Oil Cooler Hose Replacement Tips - PeachParts Mercedes-Benz Forum

rs899 · #1 07-23-2002, 02:26 PM

I just replaced the oil cooler hoses on my 83 300D Turbo this last weekend after watching my lower hose weep over the last four months since I got the car. I had read all the posts on this and other websites and talked to a mechanic or two and finally decided to take the plunge. It was bad, but not as bad as I had expected. For those of you who have this action ahead of you, I offer a few words of advice. This is not intended to be a detailed step-by-step procedure, just some tips/observations of the things I did that worked for me. Keep in mind that I have done this only one time, and I am sure there are several ways to do this successfully, but this worked for me THIS TIME.

1. Remove the left hand motor mount . This was tricky. It is difficult to even understand the concept of how the mount works and see the three fasteners holding it. From the bottom there is a hole to stick an 8mm allen key or socket on a bolt that holds the engine to the mount. After this is out, you jack up the engine and can access two bolts with 6mm socket-headed bolts that hold the mount to the "frame" Be very careful with these because if you strip out the socket heads it will be a nightmare to get these out.

2. Try to loosen the lines at the oil cooler, using a wrench on the line and one on the flange on the cooler. Do not apply much force here because you may strip the threads (aluminum to steel interface can corrode)or bend/break the soft cooler housing (I have done this on a Triumph). If they don't budge (mine didn't- rats), I would suggest you cut the rubber hoses , remove the cooler and bring it to the workbench. There, you can carefully cut across the threads of the female steel coupling nuts. Cut as deeply as you need to, but try not to dig into the aluminum of the flange. When you have weakened the connector sufficiently, stick a screwdriver in the cut and twist, expanding the coupling slightly. Then, you can carefully loosen and take the coupling nut off and dress the threads for the new hose. If you have been careful and have not cut into the flange much, the cooler can be reused. The seal is made by the bevel inside the male flange compressing with the oil line , not the threads.

3. On the block, under the IP , there is an L-shaped bracket that holds the lines together in front of the oil filter. I removed this (two 13mm bolts hold it to the side of the block) and it really seemed to make life easier to remove and replace the lines. Once I had the lines routed , located and secured loosely to the oil filter housing , I replaced the bracket (which was difficult because your arms aren't hinged properly- you'll see what I mean).

4. I tightened the lower oil line on the filter housing before the upper. There is very little room in there to swing a wrench (I used a 1 1/16th- it works). If I had a wrench to sacrifice I would cut it down to fit (maybe needs to be 6 or 8") or possibly cut out a piece of the box end (make a sort of tubing wrench).

Anyway, I got it over and done with. It doesn't leak and I didn't ruin the $300 oil cooler. Took me the better part of a weekend but I work slow. Any I didn't utter any German oaths.

To those of you who are destined to tackle this- best of luck. It can be done. And now...ONWARD... to the front end work...

surfblau · #2 07-26-2002, 01:10 PM

I was just working on my IP trying to get rid of a hot idle problem, when I put my hand on the oil cooler (small radiator looking thing)- it was cold. This after a 45 minute drive home with a fair amount of stop and go.

Does that sound like a correct condition to you, or should I be looking into it and searching for a thermostat of some sort?

thanks

engatwork · #3 07-26-2002, 01:49 PM

That sounds right surf. You would have to get it out on the freeway at high speeds with the a/c going to get the oil thermostat to open up. Stop and go city traffic does not load this engine up.

surfblau · #4 07-26-2002, 02:11 PM

You know how it is with these cars (when you are new to them). Working to fix something that you know is broke, then you see something that doesn't make sense and you start thinking- I wonder if that is also broke and I just don't know it...

thanks

coachgeo · #5 06-23-2003, 03:05 PM

ok..... dumb question.....

Do you have to drain the oil first. Sorry I dont have a manuel.

Not sure if I got to drain it all or just expect to loose the oil in the lines and oil filter housing.

Im about to attack this job.

JimSmith · #6 06-23-2003, 03:24 PM

coachgeo,

If you loosen the filter cannister top and lift it far enough to let the contents of the filter housing drain into the oil pan, you will only have the volume of oil in the cooler and lines to worry about.

Once you finish the job though, I would be inclined to change the oil, just to make sure any rodents and bugs that might have crawled in while you were not looking get out of the system before they dissolve...

To answer your question directly, the only oil that should come out is what is being stored above the lowest point you will break into the system. For most of these cars that does not include the oil pan volume. There won't be a siphon effect, and you will minimize the spillage mess if you open that oil filter cap and drain that volume to the pan. Good luck, Jim

coachgeo · #7 06-23-2003, 03:43 PM

Thanx Jim,

I was assuming all I needed to do was crack the filter cap like you said buttt.... having had the ASSUME thing make an ass out of me more than once; these days to save time and aggrivation I just ask someone first.

Thanks again.

#8 06-23-2003, 03:56 PM

I replaced the lower one a couple years ago. Lets just say it was a ROYAL pain in the a$$! After seeing many posts about removing engine mounts I'm thinking this would make things easy. Should have done them both but didn't.

coachgeo · #9 06-25-2003, 12:01 AM

ARe you kidding..... it was a SINCH

see why it was such a sinch for me here

removing 617 oil cooler lines

Here is a teaser

coachgeo · #10 06-25-2003, 12:02 AM

Found out the hose ends are
15mm and 1.5 thread pitch
Seems both ends are this thread and pitch

I got the two cooler ends done as elbows. Better for my application. I think stock is one hose has an elbow and one does not.

I don’t know about the flare fitting correctly I forgot to have him check that. I'll call tomorrow before they build the hoses. They were minus one fitting and had to order it.

I went with a shop making them cause yes....... as stated earlier the prices are about same as MB buttttt. I think mine may be a little longer. Maybe not but just in case I went with having them made to the lengths I need instead of guessing that they were stock lengths. (mine were cut and spliced together to bypass the cooler while I was driving the Unimog so I don’t know the originally lengths. I did not think to keep the pieces I cut out. I did keep all the fittings though. )

(put this here too for archive purposes.. all the answers in one thread kinda thing)

coachgeo · #11 06-25-2003, 06:47 PM

Flare is fine so this hose is a go. Installed, holding oil and pressure

300sd2000 · #12 07-17-2003, 06:45 PM

I once did the oil cooler lines on both my 300SD after the first car's hose burst unexpectedly on the freeway.

I did everything carefully, but 6 months later the other car's hoses that I had so carefully replaced burst as well!!!

I don't know what I did wrong but I will never attempt the oil cooler lines again...too scary to lose all your oil like that.

Had to get both cars towed to the garage to have them fixed by dealer. Now, no problems in over 5 years.

These lines are too fragile and too important to have anything go wrong.

I wonder if the part I installed was defective? or did I not do something correctly? I bascially did everything rs899 stated in his post.

coachgeo · #13 07-17-2003, 07:04 PM

Quote:

Originally posted by 300sd2000
I once did the oil cooler lines on both my 300SD after the first car's hose burst unexpectedly on the freeway.

I did everything carefully, but 6 months later the other car's hoses that I had so carefully replaced burst as well!!!
......

Grrrrrrr..... How dare you pop out of nowhere into this old thread and go jinxing me with a post like this when Ive just redid my hoses and I got BIG trip (OH to FL) ahead of me shortly

:p

Wish me luck.

dieseldiehard · #14 07-17-2003, 08:08 PM

Get some hose that has an ID about that of the oil cooler line OD, put that and some heavy plastic tape and various sizes of hose clamps in your tool kit for the trip. That might hold a small leak if applied right, you slit the short section of hose along the side and apply it over a rupture, after taping it first, and clamp it well.

You were planning to take some tools weren't you? At least take a dozen latex gloves. I always carry a few tools and the gloves on long trips, just in case I have a problem as well as to be able to help another Mercedes driver when I find one on the road (not often I might add).
I blew a heater hose while doing 70+ MPH, I smelled the coolant and saw the steam issuing from under the hood as I quickly pulled off the highway and coasted into a gas station which luckily was close by. I am certain if my wife had been driving that engine would have been toast. The temp gauge was crawling higher as I shut the engine off. I used some hose I purchased at an auto parts place a few miles down the road and made a patch until I could get home I drove back (slowly) with the rad cap loose to avoid building up pressure.

Dieseldiehard
1971 220 (gas) 4-spd manual 104041
1979 300TD w/ ’85 turbo engine 288975
1983 300D 237300
1985 300TD 205437

rs899 · #15 07-17-2003, 08:57 PM

scary things can happen...

Just as a epiloq to my post last year, a few weeks after I replaced the hoses, one of them developed a pinhole in the rubber near the cooler and started leaking. It turns out that there was a defective lot of these (aftermarket ) hoses loose and I had one of them. So I had to go through this all again about a month later, after sweating that the pinhole would turn into a blowout.

Rick