350SDL Oil Pressure Problem After Oil Change? - PeachParts Mercedes-Benz Forum

ezrider · #1 03-07-2004, 05:22 PM

I am the original owner of a 1991 350 SDL with 159K miles on it now. I had my oil changed recently at my local MB dealer as I have done many times in the past. The engine has no history of oil pressure, or any other significant problems.

When I picked up the car after the oil change I noticed the oil pressure gauge twitching a little bit at idle, I have never noticed this before. Today after about 350 miles the pressure dropped to near zero at idle and "2+" on the gauge at 2300 RPM and above. It was always pegged at "3" at anything much more than idle in the past. I believe the gauge because I can hear some lifter noise at idle that has never been there before.

I am very interested in opinions on what might be going on here?

Thank you.

#2 03-07-2004, 05:29 PM

First things first, take it back to the dealership you serviced it at and inform them of the problem *as a result of their work*, don't let them corner you into any diagnostic fees.

What kind and weight of oil did you have put in and what does it say on the work order?

As for the possible causes, they might have put the wrong weight oil in (ex. 0W-40 insted of 15W50). Low oil level is another, hopefully not, cause.

Are there any oil drops on the ground? How much oil does the engine consume in a given time/distance?

Palangi · #3 03-07-2004, 05:39 PM

Don't drive it. Have it towed in. Could be something other than oil in there, or could be a problem with the filter.

#4 03-07-2004, 05:54 PM

Definitely don't drive it! Have the dealership send a tow truck. Insist that they pay for the tow. It is likely the wrong weight oil.

ezrider · #5 03-07-2004, 06:10 PM

My invoice from the dealer says "Lube add 8.5 Bulk".

How can I prove one way or the other what oil is actually in the car. If they put the wrong oil in it is doubtful to me that they will admit it.

Thank you.

#6 03-07-2004, 06:18 PM

Well... I'm not exactly sure how you're going to prove that.

It may be something stupid like them forgetting to replace the o-rings on the oil filter assembly. I've heard that rotted o-rings, or no o-rings at all will cause oil pressure problems.

Stevo · #7 03-07-2004, 07:05 PM

Have no idea if this applies to your car or not but on a 616 & 617 if the filter housing stem is forced in and is not properly lined up with the rubber grommet, the filter can get damaged causing loss if oil pressure . For sure take it back to the stealership that did the service.

The o rings that VeeDubTDI mentioned could be a issue also.

Palangi · #8 03-07-2004, 07:14 PM

Yes, filter grommet out of position could do that. Also the wrong filter might do that. Wrong viscosity oil wouldn't reall show much pressure difference. I don't know how transmission fluid or some other incorrect fluid would act in terms of oil pressure. That seems unlikely, however since you feel the oil may be thin, we can't discount the possibility. Maybe you can siphon a small sample, or, at least wipe the dipstick on some white paper and see what it looks like.

This is why I change my own oil.

ezrider · #9 03-08-2004, 10:04 AM

I had a ex-MB mechanic, now independent, evaluate the problem. He found the "O" rings on the oil filter stem rock hard and said they should be changed with each filter change. He said my hard "O" rings could be the root of my problem. He replaced the "O" rings but we did not get an improvement, he says the oil pump could have failed due to starvation caused by the "O" rings. He confirmed that my oil pressure is a problem and is hoping a new oil pump will solve the problem, but that it could be worse.

He also suggested that I talk to the MB dealer that should have changed the "O" rings and didn't.

Has anyone here experienced oil pressure failure due to these "O" rings?

I would appreciate any advice on how I should approach the dealer.

Thank you.

rdanz · #10 03-08-2004, 10:41 AM

The dealer will probably tell you when your car was serviced it was test driven after and everything was is normal working order when it left the shop and they can't be responsible for what happens to your car unless it was caused by something they did.

When you picked up the car did you make them aware of what you noticed? You would have to prove your problem was caused by the oil change and that would be next to impossible.

Good luck hope its not serious

PS If I'm not mistaken the O rings which you speak about help supply oil to the lifters and if defective you lifters would clatter.
Did you notice noisy lifters?

ezrider · #11 03-08-2004, 10:49 AM

rdanz,

The lifters are noisy even after the "O" rings were replaced today. They were not noisy before the oil pressure became a problem.

rdanz · #12 03-08-2004, 11:04 AM

Quote:

Originally posted by ezrider
rdanz,

The lifters are noisy even after the "O" rings were replaced today. They were not noisy before the oil pressure became a problem.

This may be a dumb question but have you checked your oil?

Stevo · #13 03-08-2004, 05:55 PM

ezrider

Again, may not apply to your engine but with a 616 or 617 those little o rings being "head" would not have that large of effect on the system. I think they might be giving you a load of crapola. maybe the other guys with your model car will know but it sounds fishy to me. I have seen them so hard they just crumble when touched and nobody changes them every oil change. Ask them to show you in your owners manual

ezrider · #14 03-08-2004, 06:19 PM

I saw a MB service bulletin today stating that these "O" rings will cause valve lifter starvation if they become hard and should then be replaced.

Thank you.

Stevo · #15 03-08-2004, 06:31 PM

ezrider

Oh, sorry I reread your post. You want those O rings to have caused the problem because the dealer didnt change them. Let us know what they say.

Steve