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Old 08-25-2002, 10:23 PM
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Join Date: Apr 2000
Posts: 459
You CAN replace oil cooler line without removing the motor mount.

I thought I would just share this afternoon's experience replacing my oil coolier line. I read the archives on this topic, and most said you had to remove the motor mount, although a couple people said you didn't have to. This was my experience replacing the line that connects to the bottom of the cooler, although the process would be the same for replacing the top line:

1) get everything loose - oil cooler-to-radiator brackets, a/c compressor (this step is key), both oil lines at oil filter housing, the two brackets that hold the lines in place

2) pull the bottom of the oil cooler out a couple inches so you have some space to work. Put some wrenches on there and see if the nut will come loose. Do this step first, because if you can't get that nut loose, you might as well stop now.

3) Open the lid on the filter housing and drain the engine oil

4) completely unscrew the line at the oil cooler. Have a drain pan ready because this gets messy. I would estimate at least another 1/2 quart of oil drained out of the cooler as I took the line of.

5) completely unscrew both lines at the filter housing and pull them out of the housing. You need to undo both lines so you have room to move the lines around and pull them out. Its a very tight fit.

6) This is the fun (read, frustrating) part: pull the pipe off the bracket that attaches to the block and push it down and back (just a couple inches). Then grab the end of the line with the rubber and fish that end up so that the end of the hose with the nut on it is in your left hand. Then continue bending the rubber line back until it touches the metal part of the same line (you are basically bending the rubber part of the hose 270 degrees back onto itself). Now fish the folded up part of the line under the wiring harness and up between the power steering pump and airconditioning hose. This part is why it is important to loosen the compressor, run its tensioner all the way loose, and push the compressor down. If you don't do this step, there won't be room to maneuver the hose in between the power steering pump and airconditioning hose and brackets.

7) Now just gently wiggle and tug at the line directly towards your body until, moving it around for clearance, and it will come out!

8) As the manuals say, installation is the same as removal!!

Anyway, I hope this helps. It was kind of tough figuring this out on my own, but hopefully no one else will have to go through this now that I wrote it out for everyone.

'84 300D

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Old 08-25-2002, 10:47 PM
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Join Date: Jan 2001
Location: California
Posts: 2,068
I think we should add this to to the "DIY" section! Great advice.
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Old 08-26-2002, 08:29 AM
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Very nice instructions. I'm now prepared to tackle this apparently unpleasant but important task.

Thanks very much.

'85 300CD
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Old 08-26-2002, 11:09 AM
junior member
Join Date: Oct 2001
Posts: 592
realize this is a dumb question, but i pose nevertheless. would it be possible to run hydraulic hose to either replace the steel tubing entirely or some portion of same to make installation easier? removal would be made easier buy cutting the steel tubing into mamageable lengths. my try at easy fix.
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Old 08-26-2002, 01:24 PM
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P.S. I thought I should mention that you don't need any special tools to do this job. Believe it or not, the best tool for the job was a small (6 inch) crescent wrench. There is very little space to unbolt the lines at the oil cooler, so the small crescent wrench worked very well. A regular open-end wrench would have been too long (and a 22mm wrench would have required a special trip to Sears).

The only other thing you need is a very thin wrench to fit on the oil cooler boss. My full size crafstman wrenches were too thick to fit on there (there isn't much space inbetween the oil cooler and the nut on the oil cooler line), but I had a cheapie, no-name standard size wrench which was very thin. I think it was 15/16 or 11/16. I also had some very long 1/4 inch extentions which helped remove the bolts holding the lines to the brackets.

Good luck,

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Old 02-09-2003, 09:22 PM
Fredmburgess's Avatar
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Join Date: Apr 2002
Posts: 358
Great tip!

Thanks for the instructions, Greg. I just replaced both hoses on my '84300Dt. I just cut the old ones to get them out of the way, figured there had to be a trick and found your post. I already had the filter housing out for other reasons, so just removed that bracket under the IP, moved the A/C compressor, and I kid you not it took all of 30 seconds each to get the new hoses in place.


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Old 02-09-2003, 11:32 PM
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Join Date: Aug 1999
Location: Cincinnati, Ohio
Posts: 1,937
I just did both oil cooler lines and the O/F housing-to-block gasket on my '83 300SD about a month ago. I've done the job before (many on customers' cars) but it differs between the W123 and the W126 chassis. On the 126, you have to take the engine mount and the shock off to get the old lines out and new ones in. It won't budge any other way. The plus side is that it gives you an excuse to put new (or at least one if you're cheap) engine mounts in. I changed both of mine since they were flat anyways.

I WANTED to take digital pics and send them to Donnie to put up here on the DIY section but wouldn't you know it that I completely forgot my digital camera when I began tearing the car apart in my workshop!
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Old 02-10-2003, 06:01 AM
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Join Date: Aug 2000
Location: Houston, Texas
Posts: 333
Misery Loves Company

I've got an '82 240 D and have spent already about 4 hours in the removal of the oil hoses and have already got the new ones in place. I still have about another few hours to go because I still need to reconnect the new oil lines, attach the oil line brackets, attach the oil cooler, reattach the engine mount with the engine shock absorber. While I've got the front of the car up, I'm going to also change out the transmission cooler hoses (this should go much more smoothly).

This has been the most frustrating project on the car to date. I had to finally feed the new hoses through the bottom of the car while it was raised and was able to snake them through to where it is supposed to line up with all the connections. The most difficult hose was the upper hose that attaches to the oil filter. Man, if I had to do that again, I couldn't tell you how I did it because my mere accident, I got that hose snaked through where it was supposed to end up.

If you try this project yourself, you will need alot of patience but eventually you'll get them in by mere trial and error. I wish I would have read GregS comments before tackling this job, it may have saved me a few hours. Anyway, the hoses are in place, now the next step is to get everything connected.

BTW, has anybody done this little exercise on a 300SDL? I already have the oil hoses for it and am wondering if changing the hoses in the SDL is as or more difficult than the 240D.

'82 240D
'87 300SDL
'92 300D 2.5 Turbo.
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Old 02-10-2003, 01:29 PM
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I'm glad I can be of help guys. I've certainly learned an incredible amount form this board over the last couple of years, so I try to contribute when I can.

'84 300D, 173k
'90 300CE, 162k
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Old 02-11-2003, 12:03 AM
lrg lrg is offline
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Join Date: Jul 2001
Location: San Francisco
Posts: 1,163
As one who did this job on his 123 sometime ago I offer one last bit of advice. Note how the hoses fit before you remove them and pay attention to how you got the old ones out. I was in such a hurry pulling the old ones out I didn't pay attention and had a tough time figuring out the right way to wiggle them back in. I got it done, it just too longer than it had to.
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold
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Old 02-11-2003, 09:28 AM
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Join Date: Apr 2002
Posts: 358
I can relate to that, LRG! Since I had new hoses anyway, I just cut the metal tube portions of the old ones and yanked those suckers out thinking I'd remember how they fit...(yeah, right...should have taken a digital photo first!). Anyway, between GregS's post and a great photo in the Haynes manual I got them back in correctly. (...and I got the broken # 5 glow plug out with a drill and an EZ out without trashing the head...phew!)..All in all a good evening in the garage!

Thanks all for contributing to this board. This car is my daily (business) driver and hobby all in one made possible and enjoyable by the info posted here!

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Old 02-11-2003, 11:59 AM
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Join Date: Oct 2001
Posts: 592
i'll chime in ....

replaced my oil cooler lines on 83 300d t in august, i believe. to this day i have no idea how i managed to remove the old lines. not a clue as to how i managed to get the new lines in. do remember this. did not touch the engine mount. it can be done. i did it. i just don't know how! now this is a very helpful post!!
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Old 02-11-2003, 07:18 PM
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Join Date: Feb 2003
Location: Houston, TX
Posts: 48
I replaced my lines on my 84 300SD about 6 months ago. I remember I had oil all over my arms/hands (some in my hair before it was over) and I did spend time to drain everything I could.

I got the hoses out without removing a motor mount but it was a pain. I remember that at the begining, I had not removed the bracket that attached to the block. I wrestled with the new hose for an hour before I finally decided to remove the bracket. After that, I wouldn't say it was easy but it was manageable.

I also remember bending the "filter side" of the top hose some when I was forcing it through. I paid for it later, because I had to bend it back. With it bent just a little, the nut always crossthreaded when I started screwing it in. Luckily though I was able to bend it back without pulling it out.

Next time I'll try GregS's option, anything to make that task easier is worth a try. Thanks Greg!
02 E320 Black (198K)
85 300D Blue (147K)
83 300D Blue (299K)
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Last edited by PDeputy; 02-12-2003 at 07:10 PM.
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Old 02-12-2003, 12:29 AM
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Join Date: Jan 2003
Location: Okanogan County, WA
Posts: 108
Me Too!

I'v now acomplished this task 3 times, twice on my 123's and once on my 126.

You don't have to remove the motor mount, but it sure makes the job easier. I removed the motor mount and jacked up the engine, and didn't have to loosen the AC compressor. The toughest part of the job was getting the lines loose from the OF housing, and this too is facilitated by the engine being lifted up, more clearance between the OF housing and steering box.

The first two were done in a friends shop (on the 123's) under professional supervision. the third was on a cross country road trip from Ft Myers, FL to WA state. the oil was leaking fast, and was getting sucked through the wheel and onto the driver's side of the car. What a nasty mess! I put a cardboard deflector under the air dam, and somewhat alleviated the "blowout" but still had to make frequent stops to top off the oil level.

I ordered the parts from my Mech. in WA, which were delivered next day to a farm in rural (as if any part of the state isn't) ND. I changed the lines in a really hot and humid garage with lots of clingy flies and much sweat, as well as oil all over. My cousin let me grind down one of his cheap wrenches to hold the nipple on the OF housing, and the job was completed by sunset. ( got the parts at 3pm and sunset is at 8:30!!). Drove from eastern ND to Oregon coast (to drop off my co-driver) in 22 hours with no further problems

The job is done, and now I have leak free MB's!

Happy Motoring


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