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Exhaust Systems


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Exhaust system All went well until I tried to seperate the tailpipe from the exhaust manifold. I've tried penetrating oil & heat, but no luck. Does anyone have a surefire way to get the tailpipe seperated from the manifold?

I have been told that getting it very very hot with oxy-acetylene will do the job. It is very cramped there, so I have not tried it. Also have to buy that tip for the torch that gives the wide heat area. I have also considered pulling the manifold loose from the block and just twisting it gently. This might help you, since you will be pulling it off anyway. Interested in your solution. BTW, I have soaked mine in penetrating oil off and on for 6 months (the car is up on stands) and still no movement.

Will Samples says: separating the downpipe from the exhaust manifold (or header) is done with LOTS of heat. An oxy-acetylene torch will be needed, not a butane or propane torch. The downpipe is inside the header about 1/2" and by now is completely rusted in place. I have often had to get the end of the manifold cherry red before the downpipe would release. Naturally, protect painted surfaces from the high heat, expect smoke, and have someone helping to spot fires and apply water as needed. It also helps to have the rest of the exhaust system suspended. If not, it will put a bind on the downpipe inside the manifold and make it harder to remove. Once removed look for the metal crush ring that seals between the manifold and downpipe. The ring usually stays with the downpipe and is easy to spot and remove. If you do not see it, dig inside the manifold to remove it. While the manifolds are off, have them cleaned and blasted if necessary. Using some form of coating like Jet-Hot or some similar product is a good idea.

I was warned off the stainless exhaust by a number of experts. The fit is not always perfect, but more importantly the sound is not the same. It is more tinny. If you garage the car anyway, stay with stock. You can't go wrong.

Thanks for the advice, but it's too late. The job is complete, or at least it looked that way when I walked by my MB mechanic neighbor's house (everyone needs one of these). He agreed to do the job as he has a lift in his garage and said it was one of the most difficult jobs he's done in a while. To get the head pipe out of the manifolds reqired him to heat the manifolds to red hot and wiggle the pipes out. Once cool, he had to grind the manifold openings to get the rust pitting clean to receive the new pipe. I used a stock MB head pipe. The remainder of the system is custom built stainless. I think it was pattenrned on an aftermarket exhaust system as the alignment wasn't perfect. He was able to get it in with good clearances. No bumps or rattles. It cost me $400 from a neighbor. I have to wonder what a muffler shop or MB Dealer would have charged! He said it took him 2 days. The sound is good - has that slight growl that SLs are famous for, but I didn't find it tinny. I'll have to listen to it next to a stock system.

Frank Mallory says: I need some help getting my 250 SL back on the road. When replacing the exhaust last time, I was able to obtain a set of the early 230 SL tubular exhaust manifolds so I installed them together with an early 230 SL headpipe (TimeValve). No problem there, but somehow it escaped my attention that the injection linkage is different when these manifolds are used. There is a bracket that attaches to the side of the block that is not present on later cars, and the slotted bracket is different. Both of these parts are NLA. Does anybody know where I might find these parts, or get some information on fabricating them?

I am having a problem with heat (enough to smoke my new carpet) caused by the pipes that run below the floor. The pipes are in the right poshition and the fuel and air mixture is correct it seems, but the temp about 1 ft. back from the last bend is enough to blister the undercoating off. I don't have a heat shield and don't see one missing. Did all 250 SLs have this item? I have a temporary shield in place and it works wonders ( muffler repair pad). If I create a real shield from bent metal should it mount to the floor or pipes?

Frank says: It's a rather complex curved aluminum sheet, p.n. 113 492 03 30. It was held in place by several sheet metal screws. Check with Star Quality, Europarts, Tri-Star Pete, et al -- maybe you can find a used one. They seem to be very effective. There is also a smaller, foward one at the toe board Part# 113 490 00 30.

I have a problem with the muffler hangers, especially the center ones. My mechanic installed these 8 in. long rubber mounts over the small ones on the criss-cross and they broke off. I guess you check and replace them often or hang low.

For years I have had a problem the auto transmission gear shift lever housing on the interior of the car gettting hot. In the hot summer Nebraska days it is a real pain. And it really gets quite hot. I am lost as to the source of the problem. Does anyone have any ideas?

I think that generally the car is a hot one. In the summer heat seems to radiate thru the firewall.

I will be shipping my exhaust manifold (2 piece) to Jet-Hot for special ceramic coating. Benefits as advertised are lower under the hood operating temperature, lower engine operating temperature (15-20 degrees) and better exhaust scavenging (whatever that is). Slight horsepower gains, but would not go to the effort for that alone. Question for the group is, what was the factory original color for the exhaust manifold? The Meredith restoration book says black, but want to double check. Where mine are not rusted, they are grey, but that could just be the 30 year black paint residue. Would be grateful for any thoughts on this.

I'm fairly sure that the Mercedes exhaust headers were left in the raw from the factory which would have been a medium Grey cast iron look. You can try to duplicate that look with the products available from On the other hand, I just completely restored my engine and engine bay and I left the exhaust headers as is, seeing as they are mostly covered by that pretty aluminum heat shield.

Does anyone have any experience or recommendations for a complete replacement exhaust system?

Http:// Stainless steel, the only way to go.

Tom Sargeant: I have a stainless steel complete system from Timevalve. It is a "free flow" style which has a very throaty, "sporty" (translate=loud) tone. While this was fun for about 3 months, I am growing weary of the tone and I am considering replacing with a stock system from MB. My thought would be to order this from Caliber Motors and have all components shipped to Jet Hot coating for a ceramic coating, inside and out. This would give, I think, two benefits: 1. Would make the exhaust last indefinately like stainless 2. Would improve the airflow and scavenging. Note that the exhaust manifold has already been Jet Hot coated. Questions for the experienced and mechanically inclined: Are the benefits I note at 2 *real* and would I get "free flow" like performance without the noise of a free flow system? Are there ways to make the current free flow system less noisy?

Les Avery: I am not interested in an exhaust system with the acoustical performance you describe from your timevalve system. Ceramic Coating would probably increase the useful life of the exhaust, however, I doubt it would be indefinite. The Stainless Steel systems are not indefinite. I do believe the ceramic coated system would outlast the stainless. Exhaust System deterioration is simple corrosion. The combination of the water from the exhaust with the Iron in the exhaust system to product Iron Oxide. The Stainless Steel exhaust systems are predominately 409 Type Stainless Steel. The 409 Grade Steel is the lowest grade of Stainless, with just enough nickel to put it out of the carbon steel class and into the stainless class. In other words, there is still plenty of free iron to combine with the exhaust moisture, to propagate the corrosion, RUST. When you initially start the car, a significant amount of moisture is produced and left in the exhaust pipes. If you drive long enough, the moisture is burnt out. If not, the moisture remains in the pipes, and then promotes the corrosion. Ceramic coating the pipes and system, would retard the corrosion, as compared with bare Steel, Stainless or Carbon. As for the system performance, there will be a slight increase in the efficiency of the flow of the exhaust gas through the system pipes with the ceramic versus the steel. However the difference would be insignificant with respect to the acoustical and/or performance i.e. Back pressure, of the exhaust system. The "free-flow" performance described is more a function of the baffling configurations inside the mufflers themselves, than the fluid mechanics inside the system, i.e. Laminar flow vs. turbulent flow characteristics. The "free-flow" type systems have, in general, less baffling, thus more noise. I don't know any practical way to reduce the noise of your existing "free-flow" system. You could replace only the muffler and resonator sections, with OEM equipment. In summary, the total cost of the OEM System plus the ceramic coating versus your particular driving habits is the key to the answer to your question. Having driven my 280SL for 33 years, and replaced my exhaust system many times, I can confirm, that as your driving distances decrease, so does the life of your of your exhaust system.

I have owned a 1971 sl for almost twenty years and replaced the exhaust system with a stainless system from Timevalve Mfg. Inc. The system is complete from exhaust manifold to chrome tips with muffler and resonator included. The cost is $560. The system is made of 304 nonmagnetic stainless, no rust ever. Their telephone number is 1-800-243-1170.

About a month ago on ebay, there was a set of factory steel exhaust headers for our cars that was promoted as being very rare, first the seller had seen. My 65 Euro 230 SL has them. Are they really that unusual and others have cast iron ones? I guess if I have the Euro cam and these headers, I have the best performance modifications that can be had, without extraordinary expense? It did seem rather peppy.

From what I've been told the early SL's use the SL-R headers, and what I've seen seems to back that up. I get the impression there is a second header design that is specific to the SL-R and different than the ones on the early 230 SL's. For a 1964, you've probably got the headers like the ones shown in the upper area of then picture, rather than the cast manifolds shown in the lower area. Only question I have see here is "Was there another header design used on the 230 SL-R's"? So far I've seen nothing to indicate that there was, but would be interested in seeing them if anyone can get a picture of them.

It is likely that the Time Valve is not installed correctly, but after two tries to get it right and the noise, I am ready for a change. The noise (both from exhaust and contact with car) is the biggest issue. Also, my kids just don't understand and don't like to ride in the car due to the noise!

I can understand that you do not like the sound of the timevalve system, as that is a subjective opinion, however, I have the same unit.

Rodd Masteller: I have always had a vibration in my exhaust and today I confirmed where it is located. At the tailpipe, there is a rubber bumper fixed to the body above the pipes. There are two rubber hangers that try to lift the exhaust up against this bumper, but I have almost 1/2 inch of clearance. I get a vibration and loud banging when driving over the smallest of bumps in the road. I pushed the tailpipes down another 1/2 inch and wedged a bolt in there to make a tight fit. A test drive yielded no noise. Can I manually adjust (bend) the hooks for the rubber hangers, or will they break? I'm thinking of bending them away from each other to force the rubber hangers to stretch over a longer distance and therefor pull the exhaust up higher and tighter. Any suggestions??

I once purchased "O" rings from a local shop which were the incorrect size. They had a larger diameter than the correct "O" rings. Before you start with custom alterations you might want to explore this. I picked up a set of "O" rings at a Mercedes dealership for under $10. I believe from Star Quality the are under $5.

Richard Madison: the previous reply mentions the rubber rings that hold the pipes to the body fitting. The rings come in two sizes, one is a little larger than the other, one is for the fitting at the center of the car, the other size is for the tail location ... K&K and others have both sizes .... sometimes the wrong size ring is used. Another fix is to use a plastic wire wrapper (nylon plastic in various lengths, with ribbing to prevent pulling back through the end, don't know the official name, used to hold a bunch of loose wires together) ... wrap one of these around the O ring (between the body fastening point and the pipe) so it pulls the sides of the ring in toward each other to tighten the ring...this worked on one stubborn klunker ...

Rodd again: when I first got the car two years ago, I figured this noise was exhaust so I ordered an entire set (6 or 8) of rubber rings from Star Quality and had a shop install them (I didn't have jack stands yet). Well, the ones at the tail pipe are now looking old. They have cracks exposed when you push the tail pipes down. Maybe these were not replaced? Maybe replaced with the wrong size? Anyway, I will try to snug them up with plastic wire ties (that's what I call them). We'll see how they handle the heat. Step 2 would be buy more rubber and see if that helps. Step three is manual adjustments.

Cees Klumper: I've replaced these rings more than I care to remember. The fit on my aftermarket exhaust system is less than great, the worst offender actually being the two pipes that attach to the exhaust manifold. They are a bit too long, causing the whole rest of the system to sit just a bit too low under the car, all the way through to the very tailpipe ends. So the rings on my car not only hold the weight of the exhaust, they also have to overcome a bit of additional downward pressure. When one of the rings breaks, this causes the exhaust to touch the lower right rear fender, causing a loud vibration noise. I always cary spare rubber rings for this problem. So replacing the rings may not actually remedy your problem, or only temporarily so, if the fit of the exhaust is not good. I did try bending one of the loose brackets that holds the exhaust up from below the dual pipes, that the rubber rings also go around, and it bent so easily that I am afraid a bit more bending would cause it to crack. This being a loose bracket, it can easily be replaced. With the ones attached to the car body, I would be a lot more careful ...

Walter Klatt: I've done something that is a bit unorthodox with the muffler system. The original muffler had a bracket welded in the rear resonator pack between the two pipes. THis bracket is usually welded so that when installed there is a seperate bracket with the hooks for the rings and a long threaded rod that goes through the welded bracket. All get the picture? The bracket that is welded in on the bottom of the two pipes and the ring bracket in on the top. I've reversed the arrangement so that the welded(cut off) is on top and the ring bracket in on the bottom and flipped. THis way the entire system is a bit higher and the very last two sets of rings are tight, the rubber bumper is tight against the bracket for the muffler(far rear one). And there are no rattles. Also Cees, I've looked at mine and most other SL's and see the front two downpipes from the manifold are indeed a bit lower than the rest of the system. Also applies to the W108 and W109 sedans too. Could be the engine mounts are riding lower or the muffler downpipes are too long. Hope this will help those with loose hanging mufflers.

Cees Klumper: I've heard from several sources that a crack / leakage in the system can affect performance / tuning of the engine. Having said that, I have had problems keeping the exhaust pipes bolted leak-free against the exhaust manifold and have not noticed any differences in engine performance before/after fixing this.

Dan Caron, about an exhaust system rubbing agains 205-14 titres at the read: “your S- pipes are on backwards. You will probably need to get new ones and have the old ones replaced. If you look closely you will see that one end of this pipe is longer than the other and if it's installed backwards it will almost rub on the tire.”

Over the years I've tried two aftermarket exhaust systems and both have fit poorly. The main rub (literally) is against the right frame rail adjacent to the exhaust manifold. Anyone suggest an aftermarket system that fits properly?

Tom Hanson: I can get the factory original, or the equivalent from the same manufacturer without the "star" on the parts.

Doug Kim: I had the same experience with the factory exhaust! In fact, I ended up cracking the manifold because the factory downpipe was so misshapen.

Water spitting out of the exhaust pipe is condensation (much like a distillation from the exhaust - which, like all combustion product contains water as vapor - when the warm gases hit the cold exhaust). This is why one doesn't run short distances, not allowing the car (and the exhaust pipes) to fully warm up; most muffler systems rot from the inside out because of this.

Albert: I have an aftermarket exhaust system on my 230 SL, and it works very well. It's hand made in stainless steel by a specialist in Barcelona. He made the line from exhaust manifold to the end. And it cost me about 350 Euros /Dollars. I suppose the secret for a good working is "how to install" it, because he also installed the exhaust system on my car.

I had my exhaust looked at by two shops. They both said that the stainless steel exhaust system was installed correctly with no play at all. They both said that they couldn't do anything, short of replacing the system, to correct the intermittent tyre rubbing on the exhaust. I have decided to drive more sedately and avoid the problem until I need to replace the tyres, and given the distance I travel in a year I may have to put up with the problem for the next 5 years.

Cees: does anyone have experience with getting the fit between the exhaust manifolds and the exhaust pipes that go in there, as tight as it should be? I have been replacing nuts, bolts and gaskets for years now, and after an initial tight fit, these joints will invariably start to loosen and leak very quickly, even when I re-tighten the bolts. Then they just will continue to leak, a bit. My last-ditch attempt will be to add one or two of the thin round gaskets on top of the one that is already in there. Is there a better way, am I missing something, or am I facing having to replace either the pipes or the manifolds?

Walter Klatt: Are the threaded rods still good and clear and crisp threads, and are you using copper nuts with expansion washers?

Cees: yes to both, my last attempt to date was brand new bolts (I assume that is what you mean by "threaded rods"?) and new original-style copper nuts (sort of slit one-third through) at the top, hard to get on, tight fit. Although these nuts seem to loosen and lose their grip sometimes easily. Also new gaskets. At first, tight as can be then, after a 10 mile drive, one bolt+nut was already missing altogether, another one could be tightened by hand!

Walter: Perhaps your manifolds (intake and exhaust) are at different thicknesses, where the bolts connect. Why not try to use some locking washers and see what happens. Maybe someone can dig up the torque specifications for those manifold bolts. Or there is a vibration that is loosening the bolts, that is not within normal specs. Can anyone help here?

Dan Caron: I bet the heating process makes them come loose. I use copper silicone sealer on that area. Good stuff. Not on the manifold gasket. Only at the flange where the pipes connect. I usually don't have this problem . I glass bead all the surfaces before installation to get a better seal which seems to help out a lot.

Cees: this morning I added two of the thin round gaskets to each of the downpipe/manifold connections. Now there finally was some space between the flange and the manifold, before there was none. So far, after a 10 mile drive, the connection has stayed tight. Moreover, this afternoon I got together with a soon-to-be Yahoo W113 member (1964 230 SL) from Amsterdam, and looking at his exhaust, I also noticed quite a gap between the flange and the manifold. So I think I have it solved. But maybe not, in which case '" I'll be back”.

Joe Alexander: What Cees is experiencing is not unusual. The hot and cold cycles of the exhaust manifold tend to unsettle and loosen up any connection on the system especially where it is exposed to the high temperatures in the exhaust. First of all the point of the connection should be somewhat clean and free from debris that prevents even tightening of the pipes. New exhaust seal rings are advised. Like Dan, I also like to use silicone sealer on exhaust systems, even though I have stopped using it on engines. The silicone works very well on high temperature parts (Used to hold the tiles on the Space Shuttle). It also lubricates the parts so they slide together tightly during assembly. Probably the most important thing is to use the correct hardware during assembly. All metal locking nuts are a must. Nyloc style nuts will fail since the nylon will melt at the elevated exhaust temperatures. I suggest that all six nuts and bolts be new. If available they will be inexpensive. My edition "C" dealer parts book gives part numbers #000931-008217 screws (bolts) six needed, #999901-008002 copper plated locknuts (six required) and 007603-042301 seal ring (two required). Also important is assembly procedure. The three sided flanges should be drawn together evenly, tightening a little and moving to another. Do not tighten anyone bolt down completely all at once, rather move back and forth tightening everything up in several passes. Improper tightening and or over tightening can result in breaking a flange off the very expensive cast iron exhaust manifold ($1000.00 ea. + - Tom? ). Fortunately these are exactly the same manifolds used on fuel injected sedans and used units are available. If you have a helper the job becomes much easier since one person can work from below while another works from above. A six point socket with ratchet handle some long extensions and a couple of wrenches are all that is needed. I like to coat the whole connection and seal rings with silicone before drawing everything together. Some people will use lock washers in addition to the lock nuts for extra insurance. Do not rely just on lock washers, they will not do the job by themselves. Smearing a little silicone on the bolt threads (trick used by motorcyclists) is also an little extra insurance against loosening. Good luck.

I had the same problem freeing the joint. After trying just about everything I could think of, unsuccessfully, I ended up removing all of the exhaust hanger rubbers and then moving the exhaust back and forth across the back of the car (when the exhaust was lowered to clear the underside of the car, of course). Acted like a giant lever arm, rotated the seized joints, and the little beauty popped right apart. Exhaust not damaged (pretty strong unless it is rotted out anyway), and I didn't have to torque it too much since it seemed to need only a little rotation to release .......

Cees: there has been some discussion on alternative exhaust systems that can be bought for our cars. What I would like to know is: are there stainless steel buyers who can truly recommend them and, if so, what make? I recall reading somewhere that, if one does relatively few short trips (that don't allow the water inside the system to fully evaporate, hence more risk of rust), the advantage of the stainless' durability is not so important. If not stainless steel, then should we go for original MB/OEM or are there good aftermarket systems? Are there large price differences between MB/OEM and aftermarket?

George Henne: I've had my Borla system for over 20 years. Under 3000 rpm, it sounds nice and quiet - like stock. Over 3000, where a 230SL engine is happiest, it sounds so good that I turn off the radio. A really nice, almost not too loud - a wonderful sound. If it ever wore out, I would buy a replacement from the same company right away, inspite of the the fact that stainless steel should not wear out. Of course, what it would sound like with a diesel I can only imagine. :=)

After rebuilding my transmission I was ready today to put a new exhaust system under my 1969 280 SL. I was sure this would be the easiest part of the whole job until I tried to get the downpipes in place. I had cut the old exhaust because it was welded together and made from different components so it was easy to get it out. But now it seems to be neccessary to lift the car at least four feet to be able to turn the pipes in their final position. The Haynes shop manual even suggests to assemble the complete system first and then bring it in place. I can not see how this is ever going to work. Has anybody had the same experience and has some advice for me? Or am I finally just too stupid...? The only way out I see, is to tow the car to the nearest MB dealer and let them do it.

I take it your new system is already welded together. You do have to lift the car quite high to get the system in place. I tried taking my old system out recently, and found I could not lift the car high enough without extra blocks. Of course it helps to only raise the rear (or front, I am not sure now) of the car and leave the other side on the floor. I remember thinking that if I could put the car on a proper lift, there should be no difficulty.

I had a similar problem about 3 years ago & the car was on a lift! I believe it was the rear downpipe that was just not shaped properly -- not angled far back enough, as I recall. My mechanic ended up re-ordering the piece twice, getting the same poor fit, then accidentally snapping the exhaust manifold from forcing the darn thing too hard. Ultimately, he had to carve a piece out of the thing, bend it back to fit, then weld up the new bend. Without a doubt, the worst part I've seen from the factory.

I have had a Borla stainless steel system for about 20 years now. It’s certainly louder than stock, especially at 3000 rpm when it free flows. I still think the sound is magnificent, like an old Ferrari. To each his own: the rich, round sound it produces enhances my fun in driving. (A standard transmission is a must if you want to play your exhaust system as an instrument: automatics shift too soon.)
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