'09 MB M272 3.0 V6 - Rod knock

[pezzy669]

Hoping there are some fellow M272 (3.0 and 3.5) owners around here that may have some input on the "normal" hot start rod knock that seems to afflict these otherwise pretty fantastic engines.

Bought my '09 C300 w/~62k miles on it last August which has been maintained pretty well by both Mercedes dealers and independent Mercedes mechanics so it has seen probably 5W-40 and 0W-40 its entire life. Appears one oil change was extended to ~12k miles (vs 10k) but with a 8+ quart sump I am sure there was no ill effects from this one oversight.

Problem is that when engine is shut down at operating temperatures it will knock pretty heavy if you start it anywhere from ~1 hour to ~5-6 hours later. If the engine has plenty of time to cool (8+ hours) it won't knock at all and does not knock on a morning cold start. Mercedes has told multiple owners it is normal and reading online it appears this issue comes to light almost from new, some owners have had luck with MB performing repairs and there are photos of the affected bearings that show significant scoring and wear. Apparently most engines had improperly sized bearings installed so the fix is to replace all the rod bearings with tighter tolerance bearings.

I have an extended warranty going through the next 2 years and I believe I have a $100 deductible. My annual oil change is coming up in the next 60 days, so my question is should I even try to get MB to address this or am I in for a fight? Currently at ~73.5k and oil was last changed at ~65k, won't hit the 10k mark on this change as I did not drive enough so looking at ~9k on this oil run.

Any other M272 owners have this successfully fixed by MB under warranty or extended warranty? I don't have the time or patience to fight the dealership or my extended warranty company on this. Seems there are some high mileage M272 that have had this issue from new with no major ill effects later in life, sounds like the old GM piston slap issue where it is obnoxious but does not seem to significantly impact its lifespan.

 

[RooflessVW]

Take the car in for service. Tell them your concerns and that you have an extended warranty.

The tech will want the job, and the service writer will call your warranty and make it happen.

 

[pezzy669]

Originally Posted By: rooflessVW
Take the car in for service. Tell them your concerns and that you have an extended warranty.

The tech will want the job, and the service writer will call your warranty and make it happen.


Thanks for the heads up, I have never dealt with 3rd party extended warranty companies before so was not sure what to expect. I guess looking at the larger picture it would just be a bill from the dealership to the warranty company and to the dealer its more $$$ in their pocket so that makes sense.

 

[RooflessVW]

Originally Posted By: pezzy669
Originally Posted By: rooflessVW
Take the car in for service. Tell them your concerns and that you have an extended warranty.

The tech will want the job, and the service writer will call your warranty and make it happen.

Thanks for the heads up, I have never dealt with 3rd party extended warranty companies before so was not sure what to expect. I guess looking at the larger picture it would just be a bill from the dealership to the warranty company and to the dealer its more $$$ in their pocket so that makes sense.

Exactly. Now, depending on the cost of the repair, the extended warranty company may send an adjuster to speak to the mechanic. It will likely still end with an approval if the concern and repair is valid, but it can add some time.

 

[turtlevette]

How long does it knock after hot start? I wonder if a preluber or straight weight oil would cure it.

In Atlanta you could run redline straight 40 or 50wt.

 

[pezzy669]

Originally Posted By: turtlevette
How long does it knock after hot start? I wonder if a preluber or straight weight oil would cure it.

In Atlanta you could run redline straight 40 or 50wt.



Its a good 5 seconds of heavy knocking, seems to be worst around the 2-3 hour mark and somewhere around the 6+ hour mark after shutdown it cools enough to not knock.

We get pretty cold here during the winter so 20's to high teens are not uncommon for us during the depths of winter, don't think a straight weight would be an option for year round use here. We saw about 10 degrees a few winters back, those kind of temps are unusual but not unheard of.

 

[Smoky14]

Originally Posted By: turtlevette
How long does it knock after hot start? I wonder if a preluber or straight weight oil would cure it.

In Atlanta you could run redline straight 40 or 50wt.


With respect, it won't cure anything. Covering a condition with thicker oil only covers up a problem until the warrantee has expired.
Fix it right and soon.

Smoky

 

[Andrew1972]

Just see what transpires at mechanic. If a third party warranty expect your mechanic frustrated as company will not make this easy.

If fight ensues with warranty company an upside is you can easily trade this car in with symptoms masked.

 

[Audios]

Be ready for a fight. The warranty company is going to have you authorize the tear down to find the affected part, Im guessing an 8-10 hour diag charge. If they find whats failed is covered, they will pay for that and that alone, so you're probably going to be on the hook for something, a few hundred. If the part that failed isn't specifically listed in their covered repairs area, then YOU WILL BE ON THE HOOK FOR EVERYTHING. I had this happen on an Explorer, they found that the part that failed wasn't covered, so we were stuck in the middle with a disassembled engine in our bay while the guy fought it out for a few days. He ended up buying a used motor which we installed. I cut the diag down of course, but I had to get something for the 2 days of tear down and dead lift time. Ended up costing him more than if he had just bought a used motor to start. Other times, Ive seen the companies just ask for an oil sample and saw the metal particles in it, and Ok'd a rebuild, but more times than not they want to put you in a tough spot to save themselves some money. It really comes down to the warranty company and their policies.

 

[SatinSilver]

Which warranty company is it? You can PM the name if you like to keep it off here. The few warranty companies that are worth dealing with are from the manufacturer and Carmax. Otherwise, good luck.

 

[Yah-Tah-Hey]

Those so called warranties are nothing more than high cost insurance policies. Paying out claims is the last thing those companies want to see. They will go to great lengths to avoid having to repair anything. Billy the Kid had to use a gun to rob his victims. Good luck and all that.

 

[RooflessVW]

Not all warranty companies are bad. There are quite a few that are a pleasure to work with and only send adjusters out as a formality. Carmax and Fidelity stand out, and have payed out 10k+ several times, on cars I was personally involved with, without batting an eye. I'd recommend a Fidelity Platinum warranty over even OEM plans.

Some can be a challenge, but a good service adviser can sell to a warranty company just like they can sell to a customer.