When is an oil leak not an oil leak? - PeachParts Mercedes-Benz Forum

Jeremy5848 · #1 06-19-2008, 12:32 AM

Thought I had an engine oil leak in the '85 300D-T (W123, OM617). Put the front end up on ramps, sprayed the underside with engine cleaner and hosed it off. Looked all over underneath, couldn't find anything except it appeared to be mostly on the left (driver's) side. Tightened the lower oil-pan screws, the uppers were tight. Checked everything else I could get at including the oil filter cannister. No obvious source for the leak.

Leak continued, getting worse. Took the car to my indy for a check (I'm getting the car ready to sell), asked him to look for the leak while he was going over the car.

Turns out it was a biodiesel leak -- the injector return hoses are bleeding biodiesel through their walls, not having been updated to Viton (I have a kit on order). I had suspected a slight leak but it was a lot worse than I realized. The biodiesel has been oozing down the left side of the block, dissolving the 20-year-old coating of oil and dripping onto the drip pan, looking like an oil leak.

The wrench will change the return hoses, clean off the mess, and make sure there are no more leaks. I'll change the return hoses to Viton when the kit arrives and that will be that.

I pass this learning experience on so the rest of you don't have to repeat my stupidity.

Jeremy

JimmyL · #2 06-19-2008, 02:38 AM

Been there and thought that. It drips down the engine and mixes/cleans off oil on its way down and ends up looking like an oil spot.
Perfectly understandable.......

vstech · #3 06-19-2008, 08:52 AM

viton is not needed though.
a fresh set of standard return hoses will give you great service for a good long time.
those hoses sure do make a mess as they weep.

turbobenz · #4 06-19-2008, 09:10 AM

I thought this thread was going to be about when a small leak is enough to be considered a problem..

I have a small leak on the oil cooler line where it connects to the canister. If you clean it you can drive it 100 miles and it you cant even see it. Its just enough to collect dirt

Chad300tdt · #5 06-19-2008, 09:34 AM

Quote:

Originally Posted by turbobenz

I thought this thread was going to be about when a small leak is enough to be considered a problem..

I have a small leak on the oil cooler line where it connects to the canister. If you clean it you can drive it 100 miles and it you cant even see it. Its just enough to collect dirt

IMO, ANY weeping/leaking on the oil cooler or the hoses is cause for concern. Watch your gauge like a hawk and get them replaced ASAP. Less than 3 miles of running the motor with catastrophic oil loss will do it in.

Who knows when it will decide to let loose?

turbobenz · #6 06-19-2008, 09:36 AM

its at the metal fitting to the oil filter housing. No rubber is involved

Chad300tdt · #7 06-19-2008, 09:40 AM

Quote:

Originally Posted by turbobenz

its at the metal fitting to the oil filter housing. No rubber is involved

If tightening it up doesn't stop it, you can get new "screwed in nipples" at the dealer that go between the cooler line fitting and the filter housing. Maybe your lines were replaced before and the nipple got "galled".

Jeremy5848 · #8 06-19-2008, 12:02 PM

Quote:

Originally Posted by vstech

viton is not needed though.
a fresh set of standard return hoses will give you great service for a good long time. . .

The little jumper hoses were last replaced in June 2007 and probably should have been replaced a few months ago.. So, it looks like a year is absolute max lifetime on a steady diet of B100 biodiesel, maybe longer on blends.

Chad300tdt · #9 06-19-2008, 12:05 PM

I've read that you can use urethane hoses as well as viton or viton lined hoses.

EDIT: Here's the thread where I read it and the member posted links where you can get it:
http://www.peachparts.com/shopforum/showthread.php?t=223934&highlight=urethane+hose

Jeremy5848 · #10 06-19-2008, 12:17 PM

The source at that link is US Plastics. A product that looks interesting is "Urebrade(R) Reinforced Polyurethane" here. Has anyone here actually used stuff like this with B100?

sixto · #11 06-19-2008, 01:26 PM

Looks like the stuff you see at Home Depot.

Temp range is kinda skimpy for underhood use.

Sixto
87 300D

Jeremy5848 · #12 06-19-2008, 03:42 PM

Yeah, 175F is not too great. I wonder how this stuff would do after a year of being exposed to an underhood environment? Sixto, why don't you do an experiment, get some, put it on your car, let us know how it goes.

Chad300tdt · #13 06-19-2008, 03:54 PM

The stuff in the second link is rated for 220˚
http://www.shopprocycle.us/productdetail.htm?productId=5362260&catalogId=&searchProducts=fuel%20line

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