Pagoda SL Group
W113 Pagoda SL Group => General Discussion => Topic started by: Longtooth on July 07, 2006, 23:05:36
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I need to remove, have it resoldered and pressure tested, then replace it. My question is whether the removal can be done by only removing the injector pump 1st (and associated hoses, lines, and electrical connects)?... or is there a lot more involved.
I searched key words "oil cooler" on this site but couldn't find what I'm looking for. Also went thru my big blue MB repair book with same results... in fact, the big blue book doesn't even mention the oil cooler that I can find.
I developed a small water leak (1/2 gallon coolant per 150 miles at high speeds.... less at lower speeds or none around town driving) in a seam on the exchanger... which is just below the injector pump on left side of engine.
It looks like (my best observation without jacking the car up) it can be removed after removing the injector pump, but I can't tell for sure if that's all I have to remove to get to it to remove and reinstall. Since my MB manual doesn't even mention the damned thing (has all MB models with updated info thru 250SL's)... my normal resource for deciding what I'll repair / replace, and what I'll let a paid mechanic do is for naught.
I was also told that the exchanger can't be bought new ... so repair is the only way to go without bypassing it. The exchanger is original equipment on my car... was flushed, & pressuure tested and re-installed on car when engine was sent out for rebuild... and I live just South of San Jose where summer temps run well into the 90's and low 100's from time to time... more often than not in the mid 80's.... so driving at high speeds on those hottest summer day's needs all the help I can get, but never red-lined or even close, even in slow to no go traffic jams with 90F+ temps... otherwise, the temps stay just below, at or just above the normal range circa 180F on my coolant temperature gage.... oh, and I use the A/C when temps hit over 90F even if the top's down.
I discovered the leak (though not the source) embarrassingly at the beginning of a 1st Sunday Drive in the Bay area... sitting the parking lot before starting the event, there was a little trickle of green water coming from directly under my engine... right out there for everybody to see. Darn... don'tcha hate it when that happens? Hadn't had any leaks I'd noticed before... and look under the car when I park in garage every-time (just in case).... so this developed enroute to the 1st Sunday Drive. Anyway, I drove the 1st Sunday drive all out up hill, down dale, all around in 70-80F weather... had a ball (hadn't rev'ed and clutched so much since I was a teen-ager) and the temperature gage didn't waver much off normal... except on the longer down-hill grades when temperature dropped below normal. Checked and added 1/2 gal. coolant to get back to the mark when I got home (had topped up to mark before leaving that mnorning).
Strangly the leak/drips stopped by the time I'd arrived home, and after driving the next few days around town there was no further indication of a leak... and I was looking for it judiciously so I could pin-point the source or at least figure out what it wasn't coming from. It finally re-appeared after an 18 mile run to work at 85 mph... dripped onto the pavement when I parked at work.... so i crawled under the car (with my normal jeans, nice shirt work attire --- we're a relaxed bunch of engineers here) and saw the drips coming off the bottom of the heat exchanger... so from above I could see a wet line at one of the seams.... which was oozing coolant slowly.
Do any of you mechanics out there know if the heat exchanger is mounted to prevent stresses and vibration fatigue at the seam(s)? I ask 1) because I'm an engineer, and 2) because unless there's a fatiguing element involved, or un-necessary force/bending stress n the seam, there's no reason for it to fracture and leak. Solder's (60-40) a notoriously poor material for resisting mechanical fatigue...it's too brittle.... but that's what's used so I don't want to go thru this proceedure (or pay for it) twice in my life-time on the same part.... I've got this thing (compulsion is more like it) with doing it right the 1st time. Is there supposed to be some kind of vibration absorbing rubber mounting or material between whatever it's mounted to (a bracket off the engine, or a feature for mounting on the block???) and itself?
The only fatigue related stress by design should be ("should be" as spoken by an engineer) thermal expansion / contractions, and pressure changes in the water jacket, which from a fatigue point of view would cause stresses to change only a few times per drive (operation up to temperature).... say max 10x from near low pressures and temperatures to max pressures and temperatures (and gradiant induced thermal stress) each operation. If the car was driven 365 days/year that would still be less than 4k stress cycles/year.... and say 10 years worth is still only 40k stress cycles, and cyclic fatigue to fracture shouldn't set in before at least 100k max stress cycles... give or take.... which would be on the order of 25 years worth of daily driving with a bunch of start/stops each day for 365 days /year. Given some normal conditions for driving 200 days/year at an average of only 2 start/stop max pressure/temperature cycles / drive, then the solder shouldn't reach fracture thru fatigue for 75 years! Even if i assume less than ideal soldering conditions (imperfectly cleaned... cleanliness = no oils or other contaminants on the surfaces, no oxidation layers --- copious use of flux, as would generally be the case in factory production modes), it should last at least 1/2 the estimated 75 years... or ~32 years or thereabouts. Which, perhaps not coincidentally in fact, is in the range of the car's age now.... but I let it sit for 15 years in the garage... so from a use point of view it's only equivalent to 24 years worth of driving... so imo, it failed pre-maturely.... hence my question about vibration damping mechanism's that may be pre-requisite on the mounting brackets.
Longtooth
67 250SL US #113-043-10-002163
95 SL500
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Hi Longtooth,
We won't hold that little coolant leak against you. Your car looked great on Sunday (mine is the gold one) We missed you at the end, did you get fed up with the slowpokes and head for home? Send me an email and I'll put you on my list of local owners.
Pete S.
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It just mountson to the bolts that hold the motor mount arm. There are no bubber buffers or insulators. They rarely leak or give trouble. It should be easy to repair but you can get them from 250S sedans as they use the same cooler.
I think I have one or two used ones around here.
Dan Caron's
SL Barn
benzbarn@ebtech.net
slbarn.mbz.org
1 877 661 6061
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hi Longtooth
there was a discussion about these heat exchangers recently, there was a picture attached to Najs' response
http://index.php?topic=4940,cooler,250
Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto
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Hello,
As Dan says, these rarely cause problems. Occasionally one is damaged from winter freezing in northern climates. It seems that I have changed one of these without removing the injection pump in the past, but it is quite a job. You may be better removing the injection pump. Maybe bad motor mounts sometime in the past caused a lot more vibration stresses on your cooler?
Joe Alexander
Blacklick, Ohio
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Hans,
Thanks, I missed the pics in my earlier search... saw the message, but didn't open the .jpg.
I see by the location of the brackets that I should be able to get to the bolts/nuts that retain the unit by removing the injector pump. What I'm hoping for/looking for though is whether I'll also have to remove anything below or besides the unit to get it out... since I'll also have to remove the metal oil input and output tubes I see.
I now also see why & how stress on the unit can be applied when the metal tubes or other even rubber hoses are mis-aligned between their end points of attachment... and the connection design doesn't allow for thermal gradiants developed between the unit and it's attachments to the metal tubes at their other end of attachment... all in all it looks like a retrofit Engineering Change that just utilized the space under the injector pump and the bolts already used to attach the engine hold-down bracket as a least changes convenient location for a quick Engineering Change. It's not like most of the engineering design features I've seen on the SL though... far from it.
I also see where the appearance of the wet coolant is from my view from above with the unit in the car.... see the annotated picture I've attached.
Download Attachment: (http://images/icon_paperclip.gif) Oil Cooler.jpg (http://www.sl113.org/forums/uploaded/longtooth/2006787057_Oil%20Cooler.jpg)
24.32 KB
Longtooth
67 250SL US #113-043-10-002163
95 SL500
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I retro-fitted the oil cooler to my 230SL without removing the F/I pump.
Just removing the engine mounting leg and rubber (support engine on oil pan...), fuel filter and plumbing should give you enough room to take it out.
New ones are available (at a price :evil: ) but the good doctor could help you with a used one....
naj
68 280SL
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Hi,
I am the 'other' guy working on my heat exchanger - actually was talking to you at the drive and looking at the exchanger install. The job is a bit nasty, so I would strongly recommend that you double check that all of the coolant hoses in that area are not leaking before you dig into the exchanger. There are at least the cold start water lines to the injector that are worth a look, and maybe some others locally that don't come immediately to mind. These might be leaking down the back of the injector body and onto the exchanger before hitting the ground. Worth a check if you haven't already.
Good Luck - hope to finish my install Monday.
Roger
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Roger,
Thanks... I remember you're peering down at my exchanger at the meet in the parking lot when I was leaking coolant out the front. I've checked the other water lines and connections that could be leaking and dripping down on the exchanger behind the injector pump.... but wasn't able to detect anything. Problem is that the leak stops when the engine cools down... and doesn't start leaking until a good long run (at least 15 miles at 80 and 80+ mph).... so this symptom is consistant with increased water pressure (hot) or increased metal distortions (thermal stresses)... not that this is the reason, only that it's a rational reason to suspect the exhanger has a mild crack in it somewhere.... and that it' opens up enough when it distorts enough on sufficient heating or thermal gradiants... or that the water pressure increases to the point where it can be forced thru a crack. The leak that occured in the parking lot on the sunday drive was with the engine and coolant already relatively cooler after having been parked at another location for 15 - 20 minutes already. That it was leaking as much as it was after a quick restart and reparking but that it hadn't consumed more than a 1/2 gal of coolant by the end of the drive and my driving home to Morgan Hill seems to suggest an intermittant condition that would fit with an intermittant variable magnitude or direction of distortion (thermal stress... or thermal gradiants induced stress). Recall also that when I arrived home in MH and parked, there wasn't a drip at all! ... so apparently whatever it is caused by had closed back up temporarily.
I'm on-call for jury duty this week, and in a bind for time related to some building construction projects I'm doing, so will probably take it in to have it checked and find the source and get it fixed ... so I can spend time driving the thing without worrying that the leak's going to suddenly open up and spill my entire coolant in two shakes a lamb's tale while cruising somewhere inconvenient for getting a tow.
Everybody I've talked to about R & R the exchanger has said words similar to yours... it's "involved" or words to that effect. If it were winter now, I'd be in down-time on driving it a lot anyway, so I could take all winter to fix it if need be.... but I hate to use up the summer / fall months with the car not in driving mode.
Longtooth
67 250SL US #113-043-10-002163
95 SL500
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Hi LT,
My first guess was thermal expansion, but that doesn't explain no leak when you got home... an interesting puzzle. For summer you may have to keep a jug of coolant and a drip pan in the trunk!
Pete S.