Odd pits found in rod bearings of 160k mile minivan motor (photo)

Some time ago someone here was running a new Hemi V-8 in a new Dodge Charger police-package sedan. He worked in a rural law-enforcement agency and received a vehicle allowance to furnish his own car, IIRC. He said oil analysis of the Charger after only a few tens of thousands of miles indicated possible bearing wear, and he had never seen that from running Ford Crown Victorias in the past.

Long story short, maybe this bearing wear is a larger Chrysler issue than people realize.
 
K-Man said:
Some time ago someone here was running a new Hemi V-8 in a new Dodge Charger police-package sedan. He worked in a rural law-enforcement agency and received a vehicle allowance to furnish his own car, IIRC. He said oil analysis of the Charger after only a few tens of thousands of miles indicated possible bearing wear, and he had never seen that from running Ford Crown Victorias in the past.

Long story short, maybe this bearing wear is a larger Chrysler issue than people realize.
Click to expand...
The HEMI throws a lot of copper when it's young, but it's not from bearings.
 
Cujet said:
That is generally incorrect. The issue is very likely to be tuning. Higher viscosity will help reduce the problem.
Click to expand...

The next oil change on this vehicle will be to Delo 15w-40 XSP (SN, SN+)
That'll be in 500 miles on the motor since new rod bearings and one new piston. (I'm trying to clean up the inside a bit)

Do you think it would be "ok" to mix that with one quart of Valvoline R&P ?
 
K-Man said:
Some time ago someone here was running a new Hemi V-8 in a new Dodge Charger police-package sedan. He worked in a rural law-enforcement agency and received a vehicle allowance to furnish his own car, IIRC. He said oil analysis of the Charger after only a few tens of thousands of miles indicated possible bearing wear, and he had never seen that from running Ford Crown Victorias in the past.

Long story short, maybe this bearing wear is a larger Chrysler issue than people realize.
Click to expand...

If Chrysler was using straight drilled rod and or main bearing oil holes, then I would think that could indeed be an issue.
The removed bearings are most likely original and are straight drilled.
 
Tman220 said:
That pitting reminds me of the type of erosion caused by cavitation. Never seen it on rod bearings but I suppose it's possible.
Click to expand...
Since it's located primarily near the oil supply holes, I think that mostly rules out cavitation, since cavitation will generally occur at the location where pressure is rapidly dropping within the bearing.

Fatigue, on the other hand, could very much initiate near the holes. Especially when the bearing experiences cycles of overloading or excessive shaft deflection.
 
Hohn said:
Since it's located primarily near the oil supply holes, I think that mostly rules out cavitation, since cavitation will generally occur at the location where pressure is rapidly dropping within the bearing.

Fatigue, on the other hand, could very much initiate near the holes. Especially when the bearing experiences cycles of overloading or excessive shaft deflection.
Click to expand...

The only problem I see with that theory is that if you look at exactly WHERE on the bearing and the direction of the damage, and how it seems to "flow", then it looks like cavitation damage (to me)

why would fatigue follow that specific pattern? It looks like some kind of flow was going on there. It even seems to have a slight "swirl" as if it followed the oil flow.

And lastly, would'nt that exact spot be where the pressurized oil exits the oil hole and immediately decreases in pressure?
 
MaximumMini said:
The only problem I see with that theory is that if you look at exactly WHERE on the bearing and the direction of the damage, and how it seems to "flow", then it looks like cavitation damage (to me)

why would fatigue follow that specific pattern? It looks like some kind of flow was going on there. It even seems to have a slight "swirl" as if it followed the oil flow.

And lastly, would'nt that exact spot be where the pressurized oil exits the oil hole and immediately decreases in pressure?
Click to expand...
Initiation and propagation can differ quite a bit.

Cavitation usually can't initiate in that location because of the pressure gradient in the bearing. But it's possible it could propagate from cavitation if the initial failure created some odd fluid dynamics.

The "swirl" you see could be as much as result of how the material wants to fail as much as the forces acting on it.
 
Hohn said:
Initiation and propagation can differ quite a bit.

Cavitation usually can't initiate in that location because of the pressure gradient in the bearing. But it's possible it could propagate from cavitation if the initial failure created some odd fluid dynamics.

The "swirl" you see could be as much as result of how the material wants to fail as much as the forces acting on it.
Click to expand...

I love the science behind engine building and I actually enjoy it, so this kind of info is Gold.
Learning is a never ending path...no matter who you are.
Thanks !

Oh.....do you think that the chamfer in the new rod bearings that replaced the old ones (that had no chamfer) will help reduce or eliminate this problem (along with higher viscosity oils)?
 
MaximumMini said:
I love the science behind engine building and I actually enjoy it, so this kind of info is Gold.
Learning is a never ending path...no matter who you are.
Thanks !

Oh.....do you think that the chamfer in the new rod bearings that replaced the old ones (that had no chamfer) will help reduce or eliminate this problem (along with higher viscosity oils)?
Click to expand...
Chamfers are good as the helps ease pressure gradients with softer transitions. But I have no way to know if "better" means "good enough" and bearing analysis is outside my expertise. Heck, we still don't even know what engine this is, as the OP hasn't shared anything beyond "minivan engine" that I've seen.

As far as rod bearings go, there's essentially no upper limit to viscosity as you won't be able to created local bearing speeds high enough to cavitate due to viscosity. But directionally better and sufficient aren't the same thing, and it's possible for thicker oil to help while still not preventing the failure.

Again, not a bearing guy, but it looks to me like some fatigue initiated near the hole and as it released material, it contributed to additional bearing material removal by other means (microweld, cavitation, etc).
 
MaximumMini said:
The next oil change on this vehicle will be to Delo 15w-40 XSP (SN, SN+)
Click to expand...
If this makes you feel any better here's some links:
https://www.jk-forum.com/forums/stock-jk-tech-12/15w40-heaven-210282/
https://www.jeepforum.com/threads/switched-to-rotella-15w40.2622050/

Let me know how it goes. was gonna put 15w40 in mine but decided on m1 5w40 euro next oil change instead. All info on the 3.8 is easiest found by looking up your keyword and putting "3.8 Jeep" after. these 3.8s will be newer than yours and every oil post will have something about blah blah blah 5w20 in it but just ignore those
 
Trav said:
It does not look like cavitation. Here is something to look at, note the dark marks on the bearings.

https://www.mahle-aftermarket.com/m...b-2-1114-engine-bearing-failures-brochure.pdf

https://www.kingbearings.com/wp-con...e-bearing-failures-and-how-to-avoid-them1.pdf
Click to expand...

After reviewing these documents and the images, the damage on my bearings most closely resembles surface fatigue....localized only around the non-chamfered, drilled oil passage holes. (So only a minor case and probably not indicative of pending engine failure)
This motor more than likely did suffer from knocking and detonation at some point before I acquired it so this aligns with that diagnosis.

The engine runs great now and has good oil pressure so I'll take good care of it and run it until it shows signs of looming problems.
Worst case scenario is an engine overhaul which I don't mind if and when it comes to that. BTDT

POSSIBLE CAUSES
1. Overloading (lugging, detonation, or overfueling).
2. Uneven loading (see sections on misalignment).
3. Bearing material of inadequate fatigue strength for application.
4. Bearing failure due to surface fatigue can be the result of the normal life
span of the bearing being exceeded.

Fatigue of a tri-metal overlay. Spider web like cracks are seen on the surface
(Fig.4). Fatigue limit of an overlay is determined by the strength of the material
and the thickness of the overlay. The thinner the overlay the higher its fatigue
strength.
Overlay fatigue itself does not cause the engine failure.
However running the bearing with fatigued overlay may cause partial flaking of
the overlay and lowering the oil film thickness and after some time – seizure or
 
Last edited:
Jetronic said:
No, a higher viscosity oil is less likely to cavitate, also it will slow down the flow to the rod bearing if the cavitation is flow related (as it looks to be)
Click to expand...
What. It's more likely. Ever heard how old PS pumps whine more when it's cold out?
 
Lockasiam said:
Those systems also likely have accumulated wear and some old degraded fluid
Click to expand...
Ok.

"The effect of viscosity on the cavitation characteristics of a high speed sleeve bearing is investigated theoretically and experimentally. The cavitation characteristics, the cavitation shape and the cavitation location of a spiral oil wedge hydrodynamic bearing are investigated experimentally by using the transparent bearing and the high-speed camera. The generalized Reynolds equation is established with considerations of the cavitation mechanism based on the modified Elrod method in theory, and the cavitations of different viscosity sleeve bearings are analyzed and compared. It is shown that the cavitations are strip-shaped for both the high viscosity lubricant and the low viscosity lubricant, and in the rupture region of the oil film at a high speed, the oil vapour or bubbles are produced. With the decrease of the supply pressure and the increase of the rotating speed, the rupture area of the oil film increases distinctly. The cavitation area decreases distinctly and the quality of lubrication is better for the low viscosity lubricant than for the high viscosity lubricant. The experiment results in general are consistent with the theoretical results."
https://link.springer.com/article/10.1016/S1001-6058(15)60494-2

Bonus points for running the spec instead of thicker is better.
 
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