Main.TrailIndexPage | Engine | Lubrication


This component is part of Engine.


The engine needs oil to run. Changing the oil regularly is the single most important thing you can do to prolong the life of your engine. When your car is at rest, the oil slops around in a container located at the bottom of the crankcase, the oilpan. When the car is running, oil is pumped by an Oil Pump through holes and channels in the engine where the oil helps cool and clean the engine and provides a nice slippery surface that keeps moving parts (such as pistons) from grinding into one another. Oil has the following functions:

Oil capacity

The W113 M130 280SL total engine oil capacities are:

Sump / Crankcase: 5.5 liters ( ~ 5.8 US quarts)
Oil Filter: 0.5 liters ( ~ 0.5 US quart)
Oil Cooler: 0.5 liters( ~ 0.5 US quart)

TOTAL: 6.5 liters ( ~ 6.86 US quarts)
Total excluding Oil Cooler drain: 6.5 liters ( ~ 6.34 US quarts)
Total excluding Oil Filter change and Oi Cooler drain: 5.5 liters ( ~ 5.8 US quarts)

The "max" and "min" marks on the dipstick are a 2 liter ( ~ 2.1 US quarts) difference (5.5 liter crankcase/3.5 liter crankcase).
Ref: MB Service Manual (aka Big Blue Book; aka BBB)

Use 6.5 US quarts, but no more. The extra half quart can be used to top-off in case your engine is using oil over the course of time until the next change.

Late model 280SL's may have larger sump, and 6.8 liter total capacity. A replacement ribbed sump will also increase capacity.

Oil Filter Operation

Oil Filter Seals and parts

Oil Filter Seals

Standard Filter Seals in kit (see list)

Oil filter MB 000-180-00-09. It comes with one new large o-ring and the copper seal ring for the engine oil drain plug. See the list below for the additional seals

Additional Seals

There are three other seals that do not need changing every filter change but do deteriorate with time and need to be changed. They are shown in the picture, below the standard seals provided in the filter kit. The garden hose type seal fits on the filter head and seals the top of the oil filter element to the head (If its not there, you may not be getting 100% filteration). The donut looking seal fits at the bottom of the filter cannister. On inspection, this one feels very hard and may have a 'fried' look. The last one is in the bolt hole of the cannister. If nothing else, it holds the bolt in the bowl when you undo it and keeps the hot oil from burning up your hands.

  • A tubular rubber seal: MB 000-184-33-80
  • A rubber seal in the bottom of the canister: MB 000-184-17-80
  • A small flat rubber seal: MB 000-184-32-80

Filter Replacement

How to replace the filter

Oil Change procedure (including filters, rings etc)

(Originally provided by Longtooth)

  1. Get jack & jack up front end - 5 mins
  2. Place jack stands under rt & lft sides - 2 mins (if you're moving slow that day)
  3. Jack down car to jack stand supports and remove floor jack from front of car - 2 min
  4. Get & place waste pan / container under oil pan to drain old oil from engine - 1.5 min
  5. Get 13mm & 17mm wrenchs (preferrably socket) - 0.5 min
  6. Crawl / slide under engine - 0.25 min
  7. Remove drain plug - 1 min
  8. Loosen Oil filter bolt - 0.5 min
  9. Drain engine oil & fliter can - 10 min to very last drop (if engine cold; faster if warm)
  10. The following time (6 min) is in parallel with time to drain oil... so don't add to total time:
    1. Crawl / slide from under engine (0.25 min)
    2. Wipe off oily hands (0.25 min)
    3. Get 6 qts new oil from where-ever it was stored (2 min)
    4. Get long handled screw driver & flashlight or work light ready (2 min)
    5. Prepare 17 mm socket for oil filter can removal (0.5 min)
    6. Get new oil filter, included oil seal ring, drain plug washer ready - (1 min)
    7. Take a break --- sip a brew or coffee, or have a smoke (varies - at least 2 min, up to 4)
  11. Crawl / slide under engine with long handle screw driver, & flashlight or work light - 0.5 min
  12. Remove oil filter 17 mm bolt and pull off oil filter can - 1 min
  13. Pull old oil filter off mount & place in waste oil container - 0.25 min
  14. Check if upper oil seal ("donut seal" surrounding tapped bolt hole at filter can mount) is still in place (0.25 min)
    1. If so, press with screw-driver tip to determine if it's brittle or still has some give to it - 0.25 min
    2. If brittle (i.e. hard as a literal rock), remove it; then order a new one & bottom seals too, from MB)
    3. If not brittle (i.e. not as hard as a rock) with a bit of give to it be happy --- you can breath out now.
    4. If it's not there, look in bottom of oil filter can for it...
      1. If its in the bottom of the oil filter can, see 14.b above
      2. If its not in the bottom of the oil filter can, pray your engine doesn't need an overhaul, refer to 14.b above
  15. Crawl / slide out from under engine with filter can & bolt - 0.25 min
  16. Retrieve waste oil container with oil filter can from under engine - 0.5 min
  17. Wipe up any oil drops or spills under engine - 2 min (for spic & span floor... 1 min otherwise)
  18. Check bottom of oil filter can for metal debris --- hope to god you don't find any - 1 min
  19. Clean out oil filter can, remove old oil seal ring from top lip, wipe off outside surface - 2 min
  20. (Assuming bottom filter can seals and top donut seal are still ok, or that they weren't and after being pissed off, swearing at your wife, and getting over it, you've replaced them:) Place new filter can 0-ring seal in lip - 2 min
  21. Crawl / slide back under engine with - 1 min
    1. oil filter can with new oil filter inside
    2. bolt with new bolt washer
    3. 17 mm socket,
    4. 13 mm socket,
    5. Oil drain plug wth new plug washer.
  22. Install oil filter can & new oil filter and install bolt with washer & tighten up (17 mm socket) - 2 min
  23. Install oil drain plug with new washer and tighten up (13 mm socket) - 2 min
  24. Crawl / slide back out from under engine (leave both sockets under car for now) - 0.25 min
  25. Open hood (bonnet if you use British terms) - 0.5 min
  26. Remove oil filler cap from top of valve cover - 0.25 min
  27. Open new qrt of oil, pour into valve cover (6x) - 6 min
    1. CRITICAL STEP: While 1st & 2nd qts of oil are filling, check under car for oil leaks -- I don't know how often someone forgets to have replaced &/or tighted up oil drain plug before they start pouring oil into the engine. This is no lie.
  28. Replace oil filler cap - 0.25 min.
  29. Check (look) under engine for drips & leaks (assume none --- good job tightening oil drain & filter can bolts) - 0.5 min
  30. Drain waste oil into empty qrt containers (a funnel helps, btw) --- 8 min
  31. Clean out waste oil container - 5 min
  32. Make final look-see check for oil drips from oil drain plug & oil filter can bolt - 0.25 min
  33. Start engine - 1 min
  34. Crawl / slide back under engine - 0.25 min
  35. Watch for drips or leaks from oil drain plug and oil filter can while engine warms up - 3 min
    1. If oil starts accumuting on bolts or around / down oil filter can, tighten bolts as required (you left both the 13 mm & 17 mm sockets under the engine (step 21) --- right?
  36. Crawl / slide back out from under engine --- take both 13 mm & 17 mm sockets this time - 0.25 min
  37. Get floor jack and jack up front of car off jack stands - 5 min
  38. Remove both jack stands - 2 min
  39. Jack car back down to ground - 2 min
  40. Remove floor jack and return to it's normal abode - 2 min
  41. Put socket wrenches, screw-driver, & flashlight or work-light away - 5 min
  42. Place 6 waste-oil qrt containers with tops on in pile for next trip to Hazardous Waste Collection. - 1 min
  43. Wash up hands, arms, face - 5 min
  44. Tell the wife you've just saved your self $45 - 0.1 min.

TOTAL TIME = 85.35 minutes = 1.42 Hrs = 1 Hr 26minutes

Of the 1.5 hrs, 40% (35 min) is just clean-up and put everything back time. The actual work, excluding prep and clean-up is less than half the time or only 40 minutes max, and if I use 20% as an estimate of my liberal time allowances then the actual probable time to actually change the oil and filter work is about 32 minutes. Not that prep and cleanup aren't required, but these times would not apply to a Jiffy-Lube or mechanics shop since these would be done at start of work and end of work day... therefore allocations to a single vehicle would be near nil.. 5 minutes perhaps if I'm liberal. So in reality the most that can be saved by doing it yourself is roughly 35 minutes labor x $80/hr 40 minutes or about $45 max... but for that savings you also get the benefit of the near priceless value of knowing it was done right.

The following is the content from the old Yahoo documents on the site. It needs to be structured and edited in the correct sections of the entire document. After moving particular content to its correct place in the manual, please delete it here.

Rodd: I think I found a bad thing. After the car had been sitting for a week, I checked my oil level last night. First of all, it's a little over full, about .25" over the full mark. Secondly, on the dip stick there were some streaks of light brown in the fluid. What's the bad news? Coolant? ATF? Something else? Should I drain the oil and let it sit to see if a different material seperates out? I went ahead and drove to the gas station and filled up the tank. After the drive, I could not see the light brown stuff on the dip stick. I'll check it again tonight.

Higher humidity and cool evenings will give this appearance. The engine is not getting enough heat to burn off the moisture in the oil. It 'might' be something bad, like gas washing down the cylinder walls from rich starts and not enough running. But more than likely itís moisture that will go away with use.

Will: correct. The light brown streaks are characteristic of water mixing with oil. You get the appearance of a coffee with cream that has been blended into a thick milkshake consistency.

Rodd: if moisture does that, then I'll bet you're right on the money. The weather's been in the 20's at night here and the car had not been started for a week when I checked the dip stick. The chocolate milkshake color is a great description. Actually, up near the top of the dipstick was some of this stuff and it actually had a foamy texture. How hot does it have to get to "burn off moisture"? In cold weather (40F and below), the water temp gauge only registers up to 60C (140F) at best. I know I need to drain the fluid, replace the thermostat, and replace some hoses, but I just haven't had the time yet. I plan on insulating my garage and finding a heat source for next winter. It's just your typical attached 2 car modern generic garage in a cookie-cutter development. I just had to replace the overhead door and I picked a metal one with 2" thick insulation (R value = 9.8).

Frank: possibly from a defective oil/water heat exchanger. If it persists, try routing the water line around the exchanger. The oil/water heat exchanger is located on the left side of the engine, below the injection pump.

Will: I hang a piece of cardboard in front of the radiator to artifically raise the temperature of the cooling system. I read the oil has to reach 180F before it will rid itself of fuel or water contaminants. That was in Road & Track some years ago. Anyone have exact fugures?

Back to Rodd: I was doing the 'cardboard on the radiator' thing earlier in the year, but took it of on a rare 60F sunny day in the end of Janurary. I'll try to do the job right by replacing the thermostat, coolant, and the hoses (and there are a lot of them!). Any tricks to getting ALL the old coolant out and getting all the air out when the new coolant goes in? Frank, I've read a lot about my "new" car on line and in a few books, but honestly, I have no idea what a oil/water heat exchanger is, where it is, or what it does. Can you help me out on this one?

Regarding the oil surprises, I use Mobil 1 in my Ď66 230 SL here in Frankfurt and during my first winter with the car (it never gets much below 40 degrees here, but is quite humid) I had the shock of my life finding a string of goo the color of capuccino on the dipstick. I took it to my very experienced mechanic here, who had a good laugh at my frightened face. Apparently, this condition is worse with Mobil 1 and other synthetics. In any event, it goes away when the car is warm and when the outside temperature is above 50 or so.

What is the general opinion of synthetic oil for our 113's? I have switched on my 300 TDT and found great improvement, with a large drop in apparent consumption and a noticeably cleaner top end, plus much better cold starting (we hit -40 here at times). Cold starts won't be a problem with the SL as she retires for the winter, though I have some seal leaks which I expect may get worse with synthetic, but I can live with that. Any reason not to use it?

What is the recommended oil for a 280 SL and is it a good idea to run synthetic to help preserve the engine?

The owners manual calls for 10W-30 for most climates. I've seen other people recommend 10W-40 or even 10W-50. I think 10W-30 or 10W-40 would be good choices, would personally probably use 10W-40 or maybe 15W-40 in the summer. I actually use a 15W-50 synthetic, but ... I've read that switching to synthetic oil in an engine with a lot of miles on it can result in oil leaks. I think it dissolves built-up varnish, which was helping seal the old gaskets. I use synthetics in new or recently rebuilt engines, but wouldn't switch to synthetic in an older one. Any good brand name mineral oil should be fine.

My mechanic recommends 20W-50. I'll have to double check, but I thought my manual recommended 20W-50 also. He had the same comments about synthetic with regard to leaks.

Dan says: most mechanics actually know very little about oil. All they do is change it and fix things that break or wear out from lack of it. Biggest thing about synthetics is how much leaks out. Changing won't add that much to what's already happening. You just feel like your losing money on the ground.

I don't know much about the history of my engine so I used Valvoline 10w 40 high milage formula & I am pretty happy with it. My engine even seems to leak a little less! Don't forget to keep an eye on your fuel injection oil level because your engine oil will migrate into the fuel injection resivour over time.

My mechanic told me never to use 10W30. He said it was too light and would reduce the engine life. At the time, this didn't sound right to me, and I suspect his opinion may have been influenced by the fact that I had changed the oil myself. Opinions?

To keep it short, since I knew about old cars I have been told that synthetic oils were not made for our cars. Yes they are good for modern cars, but will eventually produce leaks where "older design" mineral oils did not. In addition to wear. This has always sound to mee common sense enough to believe it. Engineers will explain better how fluid dynamics and how products spread into different surfaces according to texture and shapes, and how lubrication requirements have to do with tolerances, and how this allows for modern engines to be more compact and require more fluid oils in order to reach all "angles". And while this is good for compactness of engines, and sophistication of engines, this is radically different in term of behavior within not so tight designs. I have never performed an endurance test or leak test with 2 type of oils and compared results in order to be able to preach about oil choices or brands. I personally use old-style Gulf.

The Mercedes store in Vancouver recommended that we use Quaker State FCI (Fleet Commercial Industrial) 15-40W in our '81 380SL (with 200K KM). We had tried using 10-40W synthetic oil previously, but the car seemed louder and small leaks from under the engine seemed to get worse. I am still a big fan of synthetics, but they don't belong in high mileage engines.

I bought a Ford T-bird, new, in 1994 and broke it in on regular oil. After that I switched to Mobil 1 and didn't ever change. I now have 206K miles on the car and it still runs well, passing the smog check every time and without a tune up. No guarantees, but I'm sold on the synthetic oil. The modern synthetic oils are great for gasoline engines, not the diesels, and I recommend them for older vehicles as well. Why? Because I have a 1946 Willys Jeep and a 72 Bronco that got switched as soon as I bought them and again have had no problems. The real difference is in the viscosity (slipperiness) and overall durability of the oil. True the synthetics don't have the acidic properties the older oils have but all that is a good thing. Over time the synthetics tend to clean out the oil passages and promote better lubrication and with a better product. There are those who rag on the synthetics but I think the new oils are worth the change. I use it in all my cars (4) and would not change.

I thought the rule of thumb was to migrate to synthetics after a rebuild, but never before.

Please don't worry me about using synthetic oil. I switched to 5W/50 Mobil 1 right after I bought my 280. I had heard that synthetic is always better, although it does tend to leak a little more on an older engine because the oil is thinner than conventional oil when it's cold, sitting in the garage. I would recommend the higher weight as that is what was originally common in most European engines up to the 80s. Only in the past 10-15 years the weight of oils used has come down (presumably as their ability to withstand the shear forces has increased) in order to reduce internal friction and save fuel. This means that newer engines may be designed with tolerances suitable to the lower weights. In any case the synthetic should be vastly superior. And as always, oil change intervals as little as every 3000mls are grossly overdone, even on petroleum based oils. Most European car manufacturers prescribe much longer intervals. Of course oil is comparitively cheap here, but modern oils are very capable of enduring for many, many miles. Tests done in the late 80s by German Automobileclubs, manufacturers and independent agencies which incorporated a second in-line micrifilter to filter out the smallest particles, concluded that modern oils are easily capable of 60000mls plus as far as their break-down, the ability to protect the engine and to dissolve, clean or suspend any deposites. Clearly the oil industry is not interested in such advances and the auto industry doesn't have much to gain here either. I feel more than comfortable going at least 10000 mls even in some of my higher performance engines using Mobil1.

I almost feel like a very old man here. I have had this discussion so many times that it seems like the whole world ought to know by now. I can never convince you, you need to research and let the research convince you. I even use synthetic in my lawnmower, etc. Spend some time talking to a good Automotive PE, and then go search some of the research on the subject (MIT) had some papers on the subject. Go look at an OLDS 350 (tests how long oil can maintain it lubrication proporties at 90% power on a specific engine) test and the difference between di-oil and syn. If you read and understand this you will immediatly switch and never look back. That said, there are some good guidelines for switching.

  1. open the oil-filler and run your finger around inside. If you get lots of crud and not just an oily finger take off the valve cover. If the valve cover is full of crud that looks like it would clog the lines then perhaps you should not switch.
  2. If the crud is tolerable, switch and drive the car hot and hard to let the new oil clean out the crud and catch it in the filter. After the first hour or so you may want to do the finger test again and change the filter (it is catching the crud). Do this until you are happy with the finger test and then change the oil again.
  3. If there is no crud change the oil and filter and go. Use the lightest oil you can tolerate the use of. I use 0-30 on an engine with 110K km's. I started with 5-30 (the lightest oil at the time) and then switched. My oil usage is within MB specifications. Only down side, and it is purly visual, is hot at idle I am at 1 ATM or a hair below of pressure. At normal driving, i.e. >2.000 rpm I have full pressure. I also put synthetic fluids in the transmission, rear axle, and pack the bearings in synthetic grease. This has given me a +2mpg in my thunderbird over 190,000 miles. The first 40K were on syn in the engine only and now the car has 230K miles on it, AOBTW, that oil is only changed every 30K miles and filter every 5K miles.

I agree totally with Tom and Nathan, synthetic is better in all respects. I have been using Amsoil in all my vehicles for the last 17 years. Bought my 1984 Saab 900Turbo new in Oct.83, and it has been on synthetic since Dec 84 - for a guy that is passionate about his cars, there is a huge sense of satisfaction when I remove the valve cover and find the interior clean enough to eat out of (well, you know what I mean). The only things I would do differently are:

  1. Add a can of "engine flush" to the crankcase (follow directions) prior to draining the old oil, to get most of the gunk out of the system before re-filling with synthetic.
  2. Synthetic does its job so well, that it will clean the sludge out of your engine. That means that if the only reason your engine is not leaking oil is because the sludge is helping to seal the gaskets, then you may get leaks. Time for new gaskets, or a rebuild! Can't blame the oil for doing it's job!
  3. There is a lot of misinformation and folklore about synthetics - just because a mechanic is competent, doesn't mean he knows anything about the science of lubrication.

Go to , there's lot of good info there.

I called Gernold at SL Tech to talk about some other things, and I told him of the debate on synthetic vs. "virgin" oil. As expected, he uses 10-40 regular oil in all cars except fresh re-built engines. He is the first to say that he himself has seen engines with synthetic used and admits they look like new. He himself owns such a car with synthetic. However, he also says that the detergents in the synthetics help to dislodge junk and in the process can cause havoc with various systems in the engine. He also states that these engines are old and were never designed for synthetic (gaskets, etc.). With that said, he noted that if you want to convert to synthetic, you need to change the oil and filter at least two if not three times in the first 500 miles to filter out dislodged deposits.

Achim says: Some folks have different opinions about synthetic oil etc. Some say that the additional components that are in these high performance oils are not good especially for very old engines. But I was also told that our engines are not as old as those sensitive ones mentioned above. I ran Mobil 1 Oil a couple of years on our 230 sedan. It was fine. Have regular oil now but believe that I go and switch back to synthetic (high performance engine, etc. If you are unsure about synthetic or not, contact MB Tech Service in Stuttgart or New Jersey directly but perhaps better not any (low) skilled mechanic at your next MB dealership. He might not know. Personally I think synthetic is fine with our cars.

The oil dipstick in my 1969 280SL's engine shows the embossed information "230/250 SL". Is there a big difference between a dipstick for those models and mine? Am I running it with the correct oil level?

If your engine number is up to (130.983) 10-005052 or 12-002820, then you have the correct dipstick. After that the number is 110-010-01-72. Let me know if you have any questions.

Joe Alexander says: Hello John, Hope the trip is going well. I thought it may be interesting to tell the group what the oil consumption on a healthy running 113 engine like yours is! Despite what is stated in the shop manuals, I believe NORMAL consumption should be next to nothing or very little. On the other hand what is permissable by the factory on an aging engine may be quite a bit more. Of course extremely hard driving would cause consumption to increase also.

John replies: Joe, after 4,599 miles, I have used about 3/4 quart of oil.

I read an article that stated that if you are leaking alot of oil out the tach cable/housing it was probably due to a plugged crankcase ventilation tube ( blow-by). Might be worth a look.

Ever since my engine was rebuilt in 1992, I've used Syntec motor oil, principally for metal protection and easier starting after four months of storage each winter; and I think it's great But it's always seemed -- this may seem nuts -- that the engine sounds louder than I remember it. And then today I heard the comment that synthetic oils do actually cause engines to run louder, and reverting to even a hybrid motor oil will result in quieter running. Really. So I have two questions:

  1. Has anyone else heard of or experienced noisier running with Syntec or other synthetic motor oils?
  2. Is there a consensus on the preferrability (i.e., minimizing engine wear, easier springtime start-up, etc.) of using a synthetic, non-synthetic or hybrid motor oil in W113s that are put up over the winter?

Joe Alexander: sythetics which tend to be thinner and this may be what may be causing a little more engine noise and could cause some increase in leakage. However the lubrication properties are superior according to most experts. Since cold start up is said to be a major source of engine wear, a thinner oil will circulate quicker coating metal parts sooner during cold starts. Sythethic oils supposidly cling to metal parts better than conventional oils during periods of inactivity. Naturally the longer an engine sits, the more oil (any type) will run off the metal parts and migrate back to the oil pan. After long periods of inactivaty a cold engine is started without good oil protection for the first few seconds until the thick cold oil is pumped from the pan. Sythetics flow quicker during these times. The best program is to start and DRIVE the car for at least 15 minutes, avoid long periods of inactivity. Pick nice dry sunny winter days even during the winter. This will keep seals from drying out. The brakes, transmission and differential will be warmed and lubricated. Engine parts will get a fresh coating of lubrication. Moisture contaminants will be be purged from the hot engine oil,the brake system and the exhaust system. The engine will go back to sleep with warm dry air in the cylinders. The warm up mechanism on the injection will continue to work without getting stuck. Your tires will stay round also. Naturally try to store your car with fresh clean oil to prevent sludge settling in the engine. This will also improve cold start protection during the winter months. I do believe conventional oils are adequate these days, however many feel synthetics are more than adequate and superior.

Dan Caron: Iíve had extensive experience using synthetics in all kinds of applications. I once sold a brand of synthetic for about 15 years. Once I got over my initial fear, I used it in almost anything. In most cases I saw improvements and in some I didnít. The whole idea that synthetic is thinner is basically rubbish. Itís not thinner at all, itís just that it contains little or no paraffin, the thing that makes ordinary oil go thick in cold weather. The molecules in synthetic are manufactured not refined as in crude and so can be made to whatever the requirements call for. In refined oil the lighter fractions will boil off leaving a heavier viscosity over time. The fact that it flows easier is simply a characteristic of itís natural properties. Not unlike millions of ball bearings all exactly the same size. This oil may leak out faster or it may just leak out. When someone changes to a new elixir they sometimes expect miracles and see their expensive oil dripping out on the ground. The same drip that was always there - itís just a more costly drip. Can you use it in older engines? Of course you can.

Dan Caron: just how much wear do any of you expect from starting a cold engine? The whole notion is highly over rated and is at best a selling point among oil companies looking for market share. The major source of engine wear, is, and has always been, dirt. Cold start up is actually the SMALLEST contributing factor. So all you confused sorts out there, consider this: on any engine that Iíve worked on that had crud from one end to the other, no babbit left on the bearing shells, deep scratching on the crank journals, ridge wear at the top of the cylinders you could break a finger nail on, valve guides so loose you could see right through them, timing chain 3 inches too long (OK, but you get the idea) and gooey stuff you have to scrape out of the oil pan - what do you think caused all that wear? Do you really believe that cold starts did all that when a properly maintained engine of the same mileage shows little or no wear? This is the stuff of urban legend.


Describe common maintenance procedures, and common faults that may occur. Describe how these may be diagnosed and resolved. Again, include diagrams, photographs and explanations. Where possible, include measures, tolerances, weights etc.

  • Symptoms when it faults
  • How to test if it is faulty - what tools to use
  • How to fix / change

Link to related components where appropriate.

Old Yahoo content

The following is the content from the old Yahoo documents on the site. It needs to be structured and edited in the correct sections of the entire document. After moving particular content to its correct place in the manual, please delete it here.

Oil Pressure

Will Samples says: oil pressure is a function of the clearance between the bearings of the crankshaft mains, crankshaft rods, camshaft, and the oil pump and related pressure relief valves. As these wear, oil pressure drops. Oil viscosity is not a significant factor in this. The best way to tell if your oil pressure is not up to spec is on a warm day, on the highway, in high gear. At normal speeds the oil pressure should be pegged. If not, you are below spec.

Where is the oil pressure relief valve on my 230 SL engine?

Frank: it's on the block, just to the left (9 o'clock position) of the distributor mount. First remove an aluminum cap (about 22 mm wrech) and then use a socket about 14mm to unscrew the relief valve. The manual says that old valves should be replaced with a newer version.

Last night I removed the oil pressure relief valve and its o.k. and not stuck. The oil and oil filter and seals were recently replaced and all o.k. Subsequently we tested it with a reliable master gauge and the oil pressure at hot idle was 70 psi (about 6 bar I think) and higher as we rev up the motor. It does blow a little smoke on idle and I was thinking if the oil pressure was lower it might reduce some of the smoke, even though the real problem is probably the valve guides (I did replace the valve seals recently). Should I worry about this high pressure? Is it normal?

Will: I checked the workshop manual and it called for a 5 atu pressure relief valve in the block and a 12 atu on the oil pump. 1 atu = 14.7 psi, so 5 atu = 73.5 psi. A 12 atu valve equals 176 psi. The master gauge is most likely correct. And, unless your oil pressure goes much over 75 or 80 psi, you are registering normal oil pressure. I am allowing a little +/- pressure on either side of the 73.5 psi spec. The high oil pressure should not affect the blow by. That is a function of the breather system, the rings, the guides, and their seals. Also, I assume you are using a standard oil weight such as 10-30, 30, or 20-50. You say your oil pressure is higher than manual specs. Tell us what you have found so we can compare to other sources. I have found once in a while, Mercedes will publish contradictory specs. And Will adds: I just found a 2nd source that gives 4.5-5.5 atu as the pressure relief valve specs. That gives 66-80.8 psi. So far you are OK. Is there more to the story?

The service manual say oil pressure should be in the range of 2-6 atu (29.4-88.2psi). The gauge on the dash always reads 45psi even at idle it never moves off. I was told that once the car comes to idle (hot) the gauge should read about 15psi. So thatís why I am questioning whether my oil pressure is reading high or should I just not worry about it?

Will: I believe that the oil pressure CAN read 15 psi, hot, at idle, but does NOT have to. Not dropping below 45 psi at any time indicates that the internal parts of the engine are not showing any wear. Oil pressure is generated by the oil pump, relief valves, crankshaft main bearing clearance, crankshaft rod bearing clearance, camshaft bearing clearance. The evidence indicates that none of these areas is significantly worn. You mention the service manual gives a range of 29.4-88.2 psi, but then you were told the oil pressure should be 15 psi. These figures contradict each other. (FYI 15 psi is acceptable for an engine with moderate internal wear, hot, at idle, and is nothing to worry about either, even though it is below the normal 29.4 psi. The technical data manual states: "Operating safety of the warmed-up engine will not be jeopardized as long as the oil pressure at idle speed will not drop below 0.5kp/cm (squared) and will raise immediately upon acceleration." 0.5 kp/cm = 7 psi. Unless there is more to the story I feel your oil pressure is OK and you should not worry.

I wonder if someone can help with this follow-up question on oil pressure. At idle, with car in gear, my oil pressure gauge is no longer "pegged" to the maximum level of 45, but drops to between 30 and 40. Is this normal for idle (700 rpm) when the car is in gear and thus under load? I use Mobil 1 10w 30. Oil pressure is fully pegged at maximum at normal driving speed. Any damage with the oil pressure dropping this low?

I've always heard that it's normal for the pressue needle to be in the middle of the gauge at idle.

This sounds quite typical and not abnormal. The gauge should peg upon giving it gas. I wouldn't worry much at this point.

Woke up this morning to find an oil leak near the crankshaft, I had the crankshaft seal replaced last summer and it may be that it has failed. I am running 20w 50 synthetic oil and had planned to change the oil this week to 10w 40. Perhaps the cooler weather with the heavy oil caused the pressure to rise to unacceptable levels. So it occurs to me that the oil pressure relief valve may have failed. Can anyone tell me where this is (assuming the car has one-it should) and how to test the valve?

I am pretty sure it is above the crank on the front of the block under an aprox 24mm hex shaped plug. It shouldn't leak to the outside but I guess it is possible. You might want to look at crankcase ventilation as well. If the crankcase is under too much pressure it can push oil out the front and rear seals.

Looks like my problem is a failed water pump. Just had it replaced a year ago, which is why I did not suspect this. The car had been making a funny noise which I guess was a symptom. Can anyone explain why there is so much oil at the scene of a water pump accident?

Oil in Air intake

I decided to change my air filter. I removed the top of the filter housing including the large rubber tube that runs to the intake manifold. I noticed a small pool of oil in the end of the tube nearest the manifold. I didn't see any in the throttle body (correct term?) until I manually opened the flap and stuck my finger back in there. There was a coating of oil on the lower surface past the flap. Is this normal? It doesn't seem like it should be like that.

The oil inside and behind the throttle body is normal for an engine with some miles on it. It is due to valve overlap and worn guides or rings. The SL engines were always considered high performance since they neared or exceeded 1 hp/cubic inch of engine displacement. This was partly achieved with a camshaft that offered considerable valve overlap. Meaning that gasses from the various cylinders could co-mingle in the intake manifold. Part of this co-mingling involves oil vapor, which you see settled in the intake.

Valve cover air tubing

The rubber tube that comes from the top of the valve cover and attaches to the metal tube that returns to the throttle body instead had been connected to a rubber tube and re-directed down past the engine and vented out. Would this increase or decrease the amount of oil in the manifold, the oil pressure, or the amount of oil consumption? I have purchased a new rubber connector for that and for the other end at the throttle body to fix this, but there is some rust in the metal tube. How can I remove this rust? Should I just buy a new metal tube?

This is a standard failure mode on this car. The tube rusts up, because of moisture in the crankcase ventilation gases. Then it plugs up, causing all kinds of strange effects, like oil flowing out of the tachometer fitting near the distributor, and out of the front and rear seal, etc. as a result of increased crankcase pressure. So the previous owner just vented it to theatmosphere. You are on the right track, replace the rubber if broken/rotten, and probably replace the tube too. Mine just crumbled when I tried to take it off to clean. I replaced it with a piece of black PVC, and just let the puritans scream. It wonít rust. The tube should have no effect on your oil pressure or consumption. It should also have no bearing on the oil in the throttle body. I will have to look at the plumbing on my car before I can comment on that problem.

I've decided that I'll replace the rubber and steel tubing on the valve cover return system and monitor the oil in the throttle. I assume it will get worse once the valve cover gases start getting returned to the throttle. I assume I will need valve work because of this symptom as well as a friend of mine telling me I had a blue puff of smoke when I started the car the other day. I can never see this from the driver's seat - he was in another car.

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