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Repair Questions and Answers.

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 #274678  by FIREM
 February 5th, 2012, 2:37 pm
We are seeing more and more engine failures related to rod bearings as our cars age.
There seems to be a trend for 02 and up having failures but there have been some pre 02's with failures.
Here are some facts and photos from my experiance.

2002 Pro Am 129,000, car appeared to have regular maintenance 3-5k OCI, various suspension parts changed, decent body, T/B -WP done @100k etc. Car also had evdience of being driven "hard". Severe brake dust build up on wheels, two wheels cracked from pot hole impact, one dented but not cracked. Mixed drive from Staten Island to NJ daily commute. Lost Rod Bearing #6 on the highway.
Bearing did not spin in the rod cap but was ground to dust in the pan
I did drive this car 10 miles to the shop while knocking severly. Recurculating debris making tear down failure analysis pretty much worthless.

2002 Special 110,000. Appeared to have been run hard. Evidence of previous engine repair. Suspect the timing belt broke at some point. Left Bank head had been replaced along with the belt/pump. Had a slight miss that turned out to be bent exhaust valves #5 cyl. During the swap process I checked and replaced the rod bearings in this engine.
All showed "Accellerated wear" for the miles.
Plastigauge confimed .002-.0025 clearence (Spec .0007 to .0031)
All Upper bearings showed "full" wear across the entire bearing.
"Normal" wear would show as only 2/3 of the bearing surface diminishing towards the parting line, like the lower shells show.
All bearings had lost their crush fit into the rod & cap evidence of heat. None of the shells had fretting evidence on the back, but they fell out of the cap and rod once the nuts were removed.
Slight evidence of heat and or extened OCI from the dark area extending near the wear area and slight pitting in some areas.
These bearings look worse in the images than they really are. Scratches are extremely fine and you could not "catch a nail" on the crank or bearings.
Main Bearings were checked, .0015 clearence, "normal" wear, and reused (sorry no pics)
I feel there are a number of factors to the increase in bearing failures we are seeing.
Hard driving/High RPM
OCI & Viscocity, as bearing clearences increase 10W-30 will protect better than 5W-30
Heat may also be a factor. Maybe that Engine Oil Cooler, deleted for 02 was more important than I realized.
Based on the above information I will be dropping the pan on FIREM some time this summer and report back what 150,000 miles with regular 5k OCI shows for bearing condition.
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 #274680  by 300maximilien
 February 5th, 2012, 3:22 pm
nice info Bob...thanks. I was going to start a thread similar to this with a poll.

I would like to reread any stories of pre '02 bearing failures if someone can point me to the thread. TYIA
 #274681  by PurpleCat
 February 5th, 2012, 4:12 pm
Interesting info, Bob. Many, if not most, of our 300M's had multiple previous owners who may not have performed proper maintenance, and it is the abuse that occurred thousands of miles back that results in wear problems today. There are many drivers who never change oil/filters, and never replace coolant which is reason for the gummy gunk coolant sometimes found.

No amount of regular oil changes and maintenance can fix damage already done.

As to protection benefits of 10-30 v 5-30 oil, may not be any unless in extreme cold climate. The lower viscosity is only in effect at engine start up and evolves to 30 weight when engine reaches operating temp. Back when Mobil-1 was invented in mid-1970's and about 10 years thereafter, it was only available in single grade 5W. I have hundreds of thousands of trouble-free miles running Mobil-1 5W in Mercedes, Audi, and Chrysler, and that is in desert heat. Never a bearing or wear problem but I started with new vehicles and had total control over maintenance.
 #274722  by user97
 February 6th, 2012, 4:44 pm
Very interesting info -- your guess about the oil cooler might be onto something...

Out of 4 LHs that I am involved with (all 3.2/3.5 engines) the one that seems to have developed some fairly subtle sort of thudding/tapping (mostly in the oil pan area) audible only at idle/when engine is decelerating from 2K to idle) is the '02 3.5 (non-H.O.). I am not 100% positive that the thudding/tapping is related to the rod bearings (have not pulled the oil pan yet). It's been doing this for about 15K so far and it has only gotten very marginally worse. Since the car is nearing 200K at this point, I am pretty much waiting to see what will happen. If it is the bearing and it eventually destroys itself, I will probably replace the engine wholesale. Based on forum posts it does not look like trying to swap the bearing in place will lead to lasting success and it hardly makes sense to do a yank/rebuild/re-install a 200K miles engine.

I don't drive my cars hard by any means and do regular oil changes/other maintenance.
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 #274733  by Maximus
 February 6th, 2012, 5:42 pm
I have been talking about the oil cooler for a while but everyone just blew it off as oh well. I to have been saying the oil cooler is very important.

Also how many times do I say you cant run these cars hard, but when Bob says it its ok.

I don't run my car over 3000 rpm and I have a 00 with a oil cooler.
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 #274775  by TrueBlue
 February 7th, 2012, 10:07 am
Quite simply, one of the most important threads on this site. All M owners should read and take heed.

Adding to the sample size: 2002 300M Special, 92K when rod noise was detected. Car was originally a Texas corporate fleet car - high heat plus impersonal maintenance for the first 60K miles contributed to a highly-sludged engine.









Keep the pics coming. Hopefully we can save some Ms from untimely deaths.
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 #274787  by Maximus
 February 7th, 2012, 3:56 pm
It may already be too late for some. I do beleive that you can nurse along a sick car by going easy. Warm it up. Don't go past 3000 rpm. Nice and easy. I feel cold starts...cold starts with high rpm...Not changing the oil every 3000...Over heating the engine.....can cause damage.
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 #274828  by TrueBlue
 February 8th, 2012, 4:15 pm ... rtcopy.jpg

An oil analysis is a great tool as well. @ $35 from a laboratory. I view it as bloodwork for your engine.
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 #275211  by Maximus
 February 16th, 2012, 8:50 am
You know what I mean.....Don't romp on it or will most definately spin a bearing if you have high mileage on your motor.

I drove all week so far back and forth to work without going over 2700 rpm and still managed to go the speed limit which is 40, but you can cruise with this car at 60 and still stay under 3000. Just dont spin it up to 6 grand.
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 #275217  by 300maximilien
 February 16th, 2012, 9:40 am
speers wrote:Well crap, according to Maximus my car is going to blow the motor soon. I am often and above 3k on the tach.
Hey Sean nice to see you posting. How is the car doing?
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 #275218  by speers
 February 16th, 2012, 9:49 am
Good bout yours? I think I have 81k on mine now..but it has now become my daily commuter so the mileage is adding up faster. I have the P0340/44 code, so going to change out the cam position sensor when I change the oil this weekend. Restarting the car clears it for a couple weeks at a time.
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 #275220  by speers
 February 16th, 2012, 9:59 am
@ Maximus..just messin with you. I agree that if you abuse a motor it will shorten its lifespan. Which is seriously why mine probably will never see 150k. I am just too hard on it. Start and stop on Wash DC beltway, fighting my way to work and back home during 1 hour commute...0 - 60/75 repeatedly. But I keep her well maintained with good synthetic oil, so we will see...if she does go south..maybe that will be my excuse to move to the Challenger...
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 #275230  by 300maximilien
 February 16th, 2012, 10:41 am
speers wrote:Good bout yours? I think I have 81k on mine now..but it has now become my daily commuter so the mileage is adding up faster. I have the P0340/44 code, so going to change out the cam position sensor when I change the oil this weekend. Restarting the car clears it for a couple weeks at a time.
Good to hear your's is well. Unfortunately the Special in my Sig developed a Rod Knock, so I sold it to a Member (Not sure if he was able to rehabilitate it yet) I bought a '99 2 years ago that I just gave to my 16 year old Son. I am on a constant search for another M for myself though!

Hope the sensor solves your codes.