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Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 8863
Experience:  I am ASE Master Truck Certified.
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We have a 3406b 7fb fresh rebuild blowing oil out the exh and

Customer Question

We have a 3406b 7fb fresh rebuild blowing oil out the exh and wore out the rear thrust washer. disassembled to check rings are correct. ring gaps are .035,.045,.030 oil piston has .012 clearence
Submitted: 2 years ago.
Category: Medium and Heavy Trucks
Customer: replied 2 years ago.
these are PAI aftermarket parts that match up size for size with the original cat parts. The oil that was used is a mobil 15w40
Expert:  Cat Man replied 2 years ago.
Hi. Thanks for asking your question and requesting me! I will try and help you out.
Was this happening right after the rebuild? Or did it take a few miles for this to happen?
Also, when you say rear thrust washer, are you referring to the turbo washer or the crankshaft thrust plate?
Customer: replied 2 years ago.
I have been PAI user for many years and I'm getting a biased opinion not being cat parts . I'm not sold on that .
The crankshaft thrust washer
Customer: replied 2 years ago.
Right from the start up there seemed to be a problem. It progressively got worse
Expert:  Cat Man replied 2 years ago.
Thanks for the information.
It's rare I see a crank thrust wear like this. When I do it always caused by the Trans pulling or pushing on the crankshaft. As I am sure you know. When there is good end play with correct size thrust. This should not happen.
Since the rings and Pistons are OK. I must next suspect the turbo pushing oil. It's possible that valve guides can do this but not common to see them push oil. They nornally just cause a oil consumption problem.
Please reply back if you need more help or have more questions. I am happy to assist.

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