Yesterday, my dad and I tackled the oil cooler line replacement project. It started out well, we were able to get the fitting off the oil housing with no problems (thanks Dieselgiant for the tip on the special tool).

Then, the upper one on the oil cooler itself came off with no problems whatsoever... but the lower line on the cooler was stuck rock hard - using plenty of PB Blaster, and gently trying to persuade it only resulted in stripped threads - see the photo. So now I have another project - fixing the threaded nipple.

Reading through some of the posts on this forum, I was able to find an excellent thread on the topic: are the oil cooler fittings replaceable by themselves?

I ordered the parts from my local dealer (I guess nobody in CO carries it) - the part referenced in the thread was # 915013-013002. Should arrive on Tuesday, meanwhile, questions on the actual repair for those of you who fought through this already: what are some of the steps for installing the patch fitting. Reading below it seems we need to cut off the nipple with the stripped threads back to the nut that's permanently attached to the cooler - that's clear, but drilling a pilot hole is confusing me... Why would we need to drill a pilot hole - isn't there already a big hole in the place where we just cut the nipple?! Wouldn't we just tap the big gaping hole in the oil cooler? Obviously I'm missing something.... and any help here would be appreciated -


Here is the direct quote from someone on the above thread:
"... All I had to do is cut the aluminum threads off the oil cooler, drill a pilot hole, tap new threads, and install the new fittings. The thread tap size is 18mm by 1.5mm. The drill size for the pilot hole is 21/32 inches, I don't know the metric equivalent. It took a local machinist 15 minutes to cut off the aluminum threads back to the nut part, drill the pilot holes (there's plenty of metal there), and tap the new threads. It took longer to rinse out all the aluminum filings and grit out of the cooler than it did to work on it. Here are the MB part numbers for the threaded oil line fittings and copper washers. MB Part # Description 915013-013002 Screwed Nipples (That's what the label said.) 007603-018101 Ring, General, Metal"

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1987 Mercedes 300SDL; SOLD
1985 Mercedes 300D; SOLD
2006 Honda Pilot - wife's ride; 122K;
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