I recently replaced a 4.2L V6 in a 97 2Wd 1/2ton with a turned #6 rod bearing for my father-in-law. He's a used car dealer and tells me that this is a common problem with the 4.2, not specifically #6 but rather rod bearing failure in general. I had some spare time so I decided to autopsy it to figure out why this is a recurring theme. What I found upon tear down was that #6 had turned the bearing in the rod. Now what I would have expected as #6 is the farthest from the oil pump was that the bearings would get progressively better the closer I got to the source of the oil flow. This is not what I found. What I did find was that #3 was still good, worn but still acceptable, #5 was worn the copper but no appreciable crank damage, #2 had the copper starting to flake away from the steel but no scoring on the crank journal, #4 was nearly new looking, and #1 was worn to the copper but not scored. I'm almost tempted to say the it was the bearings themselves that where the source of the problem, inferior quality perhaps. I was wondering if anyone else has had experience with these issues and if there is anything to be done about it?

 

Sorry it has taken so long to reply. Been busy at work and on the road a lot.

I have been hanging out here in the 4.2 forum for about 12 years and can't say that spun rod bearings is anything I would mention as being anywhere close to a common problem.

I am sure there have been a few mentioned, but honestly, I don't have specific recollection of a single one.

Early years did have bearing problems on occasions when coolant got into the oil when gaskets failed, but that was due to the coolant, not an inherent problem with the bearings/bottom end.

Seems pretty much that the bottom ends will go forever if they receive regular oil/filter changes (5,000 miles is what I do and I'm somewhere around 265,000 miles now)

 

Well my father in law has done rather well buying these trucks at auction with bottom end noises then buying a insurance write off with a good motor and putting the 2 together. it's common enough in his opinion that he keeps a motor or a complete truck around to put together a quick flip.

 

I got curious and did a search. Looking back about 7 years, I didn't see one thread documenting a spun/failed rod bearing.
Either way, I'm glad to hear his operation is working for him, and glad I haven't had to deal with the problem.
We both win.

 

Is there any way that the spun bearing was from coolant leaking into the oil?

 

The oil was coolant free, and water free.

 

I have a 96 5.0L v-8. I just installed a crank position sensor when code reader said it was bad. Info in box said that if engine was run with sensor bad, damage to internal engine parts would occur. My engine has been developing noise when reved up. Noise like maine bearings make when bad.
Crank sensor & info= Auto zone