jherman

I have 78K miles on a 2001 C320. I am a very easy driver and car has been religiously serviced at MB dealer only. About 3K miles prior to my A service at 70K, computer told me I needed to add 2 quarts of oil. I did so and immediately notifed the dealer who read the oil level with some manual gizmo. At 70K service, dealer performed an oil consumption test. Dealer first said I needed new piston rings, then backtracked and said all was within spec.

Now, at 78K and about 3K prior to B service at 80K, same message about needed 2 quarts of oil came on. Since moved and new MB dealer performed oil consumption test and says need new piston rings.

Is this possible? Anyone have any thoughts on this?

Vivid

I find it hard to belive that you need new piston rings. Thats just my initial thought.

You need to do a compression test. If a cylinder has way less compression than the rest, then yes, It is probably the rings. Not necessarily on ALL pistons though. It could be only one.

If that is all fine and dandy, it could be the valves that are causing oil consumption. Do you have black/blue smoke out of the exaust?

Buellwinkle

MB considers it normal if your car consume less than 1qt of oil every 1,000 miles. Of course that's unacceptable to most, specially with 10K oil change intervals. My C230 Coupe was worst with about 1 qt every 3-4K miles, my C230 SS is best at never needing even one qt between 10K mile intervals. MB recomends a very light synthetic oil. You don't have your location in your profile but assuming harsh weather is not an issue, switch to a thicker oil, won't harm the car and you'll be able to go further before needing to add oil. Also, look for a synthetic oil formulated for higher mileage engines.

jherman

don't know if dealer performed compression test. no blue or black smoke from exhaust. Also gas mileage seems to be fine.

Vivid

also, ask them how they perform an "oil consumption" test.

RES

Don't forget wet dry compresson test. That will tell you if it is valves or rings. If there is no change its valves if it is low and increases on wet test its the rings.

SUNILP

Do a cylinder leak down test as well if you want to be sure.

jherman

ok - here is the latest: dealer says excess oil consumption due to piston rings (don't know about wet/dry compression test or other details suggested by all who replied) but given impeccable service history by MB dealers only, MB will pay significant portion of repair even though car is out of warranty.

Problem is, my share of the repair, plus other necessary repairs instrinsic to 5 1/2 year old car make me consider trading for another C class.

mleskovar

Something is fishy here. First, that your car would need new rings at 70K miles after being 'properly serviced'. Second, that the dealer would chip in to have it fixed (out of character for a dealer, nice gesture though ). If it is worn rings I'm guessing they did something wrong to make it wear faster.... like wrong oil. I haven't heard of worn rings on this engine type yet, especially at 70K miles. New rings is a major job so I would get second opinion(s) to the exact cause before coughing up several thousand dollars. All the advice given so far about rings vs. valves and leakdown tests is right on and the dealer should be able to articulate the tests they used to determine it to be rings.

jherman

Dealer says performed oil consumption test by "marking the specs" on the oil, driving the car (100 miles, I think) and re-marking the specs. They also use a boroscope (sp?) looking for issues. Did not do a compression test and do not believe it to be valves.

My earlier post may not have been clear - it is not MB dealer contributing to repair, it is MB of America that will pay significant portion of repair to MB dealer.

RES

Sounds like assembly problem, They must have seen something with the borascope that they think is an issue. And your portion of the repaire is like a deductible, since you did get 70,000 out of it. Had the same issue with one of my other cars not Mercedes. Toyota replaced my brothers Four Runner engine at 120,000 miles from bad head gaskets no charge. Now thats service! To bad the dealer didn't adjust the valves and the engine ate it's self in 10,000. LOL!

C230 Sport Coup

Do a leakdown test.
Could be the valve guides
too.

mleskovar

Like a ring(s) disintegrating and coating the cylinder walls with metal...could be. Would also explain why they are willing to chip in for the repair since that shouldn't be happening unless there was a faulty ring(s) installed from new.

jherman

Makes a lot more sense to me than just the "you need new rings" statement from the dealer.

Many thanks to all who posted. However, I decided that even though I loved that car, it made more $ sense to get a new one in light of not only this repair, but also several little things also needing work (leaking rear differential, leaking seal in auto trans causing fluid to be slightly low, new blower regulator motor needed, new motor mounts, leaking a/c pressure switch).

Just came home with a new 07 C230 last night!

mleskovar

..... good decisioin. Sounds like the wheels were coming off your 320! Enjoy your new ride!