Report of a common problem with 4BT's

[dieselcruiserhead]

Just wanted to quickly report on something I learned a little while ago. Not sure if this belongs in the right place, for all I know might be a problem the 6BT's too. Basically the #4 bearing's OEM design is a three piece, the actual bearing and two "thrust washers" pressed into the bearing:



#2 below is the bearing. This goes top side. As you can see here one of the "washers" became seperated (sitting in the oil pan) and I got a large amount of movement on the crank. Not that big a deal but long term it can cause the crank to wear into the block.



Pretty easy to replace. I have never rebuilt and engine or ever swapped a bearing before, for what its worth...



Drain oil, drop the pan, count number 4 cover (#3 in photo above), remove bolts (#4 in photo), then remove bearing surface (that covers crank 360 of course)... Then very carefully with fingers or some sort of pry surface (being careful not to scar crank or block surface), pry bearing out of place...



Cummins improved the design and sells the replacement as a 1 piece. Pretty neat of Cummins of course... I did not take a photo of the replacement bearing out of the engine... It looks like the washer as if it were pressed together, but is actually 1 piece...



Take new bearing, cover in oil, and slide in its place. It can only go in 1 way, "the correct way")... Then bolt back cover to proper spec as mentioned in factory manual, then oil pan...



Here is photo of the new 1 piece bearing in place, with arrows show the actual bearing:



Here is photo of the pan where the washer was resting for god knows how many miles (I got the engine this way). It caused some clutch engagement/disengagement issues because there was so much play...

 

[JLEONARD]

Andre, good thing you caught this early.



I had a VW diesel that wore thru the thrust bearing... the crank had at least 1/8 end play... probably closer to 3/16 play. Anyway, I didn't find out until I heard this strange heavy knocking noise and took the engine apart to find out what was up... the noise was one of the counterweights and one rod bearing cap hitting the block from time to time. Thrust bearing was completely gone, crank was toast, and the cylinders were ALL elongated.

 

[Joseph Donnelly]

6BT's used the same type bearing.

 

[dieselcruiserhead]

Could have sworn I posted this in the Cummins conversions section. I imagine someone moved it here because the 6B's used them too? Anyway, easy fix and I honestly had some mileage with it like this with no apparent issues. I have heard those with autos have gone 30K miles with no negative effects but I would personally sooner replace it rather than later...

 

[MontyDyer]

Joe is right, last year mine went down in my truck the same way yours did in your 4bt. I was lucky, I caught it before any damage could happen. As I recall, I believe the new main set I put in also utilized the 3 piece design.

 

[Paychk]

Someone 3-4 months back was posting on this very same problem, never heard if he found a cure, I bet this is it.

 

[Philip]

Paychk I bet that was RPowell your thinking of. He had the thrust bearing gone in his truck. He had a friend put in new bearings and he is up and running now. He was at our cookout in Oct with it.

 

[Paychk]

Thanks! good to hear it is running again.

 

[swankmetal]

got a part number for that thing? good write up, btw.