Cold Weather Oil Waterfall - PeachParts Mercedes-Benz Forum

300DFarmer · #1 01-20-2008, 12:54 PM

Here's a puzzler.
On my wife's '82 300D, I just experienced the second occurrence of starting in cold weather (0F) and looking under the hood to find oil cascading down the oil filter housing. I am using a Meile filter and new o-ring, and have torqued to the recommended 25nm.
Admittedly, the first time this happened, I had to over-torque slightly in order to stop the leak.
This time, the o-ring was slightly squashed, and I had to replace it with a new one from a new filter. Torqued to 25nm, and so far now leak.
Has any one else experienced this? It's a real drag to have to out there dealing with this at low temperatures when my wife if trying to get to work.
I am thinking of trying to source a larger diameter o-ring as a replacement to prevent this from happening again. My thinking is that extreme cold causes constriction of the rubber that compromises the seal. Has anyone tried this and/or where I could find a larger diameter o-ring?

mobetta · #2 01-20-2008, 01:00 PM

how long since the filter was changed? maybe it was compromised when installed? i have had 0 problems w/ a leaky gasket, and have only heard of leaks from freshly changed, ill installed gaskets.

nhdoc · #3 01-20-2008, 01:02 PM

Maybe you just got a bad lot of o-rings in your filters. I'd have the local M-B dealer get you a couple of o-rings and try one of them out. I'm pretty sure they can order them without filter kits but it might not be all that much more just to buy the entire kit from them too.

300DFarmer · #4 01-20-2008, 01:07 PM

Filter was changed about a month ago, installed personally. This was perhaps my twentieth 300d oil change, and have not experienced this problem before. Perhaps just a deficient o-ring. Still, I'd like to consider an oversized o-ring, as upon close inspection, even when new the o-ring included with the filter doesn't provide much room for error.
My bad on the first post. Filter is a Hengst, I had just put a Meile filter in my Meile vacuum and must have that stuck in my head.

barry123400 · #5 01-20-2008, 02:53 PM

Not positive of the setup but if the pressure release valve in the oil pump is not opening the oil presure could be massive on a cold start. Heavy thick cold sludge in it is about all I could think of in the valve assembly as a cause.
May not be this but I might consider it as a possibility. I would read the oil pressure with a mechanical gauge that reads higher than the dash gauge. Thats if nothing else is found on a cold start to cause this occurance. I think it is a 60lb release pressure valve but others may correct that. Again it is only something for thought at present.

300DFarmer · #6 01-20-2008, 03:17 PM

Barry, Thanks for the insight on the pressure relief valve. I'll check it out...

F18 · #7 01-20-2008, 04:30 PM

If you are expecting consistant 0F weather you may want to run 5W40 Rotella oil. 15W40 viscosity is way to high and will cause higher than normal
cold pressure until the engine warms up(if that is what you have in there). Even a blend of half 5W40 and 15W40 would help at that temp.
Also some O Ring sources have changed the compounds over the years and some of the inferior ones tend to be too temp sensitive and shrink or loose their elasticity in the exteme cold. Once the engine warms up you are probably not experiencing any leak............

300DFarmer · #8 01-20-2008, 05:10 PM

I am running Rotella 5W40 synthetic in this engine. Definitely helps in cold weather.
I am beginning to think that perhaps the filter bypass system is not working correctly. I doubt that at 0F that the filter media is able to pass oil. In this case, the filter bypass would be activated. My thinking is that if it does not work, that increased internal pressure would result and oil would find its way out. Once the oil is warm the filter would work correctly and leaks would lesson. This theory make sense to me since the car leave a fair amount of oil where it parks, but never seems to lose a lost of oil during operation. If it was losing an amount of oil consistent with the stains on the ground, I would expect to be having to add a qt of oil every couple of days.
Does anyone follow me on this?
Any experience with a faulty bypass?

kerry · #9 01-20-2008, 05:34 PM

Quote:

Originally Posted by barry123400

Not positive of the setup but if the pressure release valve in the oil pump is not opening the oil presure could be massive on a cold start. Heavy thick cold sludge in it is about all I could think of in the valve assembly as a cause.
May not be this but I might consider it as a possibility. I would read the oil pressure with a mechanical gauge that reads higher than the dash gauge. Thats if nothing else is found on a cold start to cause this occurance. I think it is a 60lb release pressure valve but others may correct that. Again it is only something for thought at present.

My thought exactly.

300DFarmer · #10 01-20-2008, 05:38 PM

Does anyone know what kind of oil pressure is generated on start-up?
My service manual states that the relief valve is set to operate at 7 bar.
At 2000ft altitude (where we're at) 7 bar is just over 100psi.
I have to imagine that I could be surpassing that amt. at startup, especially when it is 0F or colder.