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
