Main Bearings on Detroit Diesel 14L, Series 60

Depends on engine, some as low as 600k. It's an easy job, maybe take you an afternoon. Requires a big torque wrench.
Think of it this way, if that crank goes, the engine is likely gonna be ruined. Bearings are about 700 dollars, a crate engine is over twenty grand.

 

I'm actually curious about this. How are the two related? Oil pressure and main bearings. My series 60 (14.0L) stays over 50psi during normal operation at 1200rpm/61mph. Always seemed normal and never had a mechanic raise any red flags about it. I'm sitting at 660k on the odometer.

 

That is why you should take an oil sample, all will be revealed..

.... Philip

 

It's the same on big trucks. But when you wait for a big drop in pressure, you risk crank damage. Ona small block chevy, no big deal to yank the engine our and slap in a new crank. A cumalong and a solid tree branch is all it takes. A big diesel, not so easy and thousands more for a crank.

 

Rod and main bearings are nothing but a metal sleeve with oil pumped in between them and the crank for constant lubrication. As they wear tolerances increase and oil starts escaping out the sides and your pressure starts decreasing. The more they wear the more the oil pressure drops. There are more parts that rely on lubrication like the rings can let more oil by as they wear. Cam bearings too. That's one reason when you do a rebuild you can buy oversized bearings and rings. They just machine down the worn parts and add bigger stuff to restore the tight tolerances.

Checking bearing tolerances is actually fun. You use this stuff called plastigage which looks like wax string. You stick it under the bearing and retorque it back down. Then you take it back apart again and see how much the string squished and compare with the gauge on the package.

 

hi there;; i just find out also bout that today an older driver told me to change the rod and main bearings on the crank shaft in the engine ,,i have a freightliner 14.lt 60 series and my oil pressure its also between 45 to 55 psi on normal operation,,but he recommend it me to replace them since my truck its at 911200 miles,,so im curious also if it really needs to be done,but he scare me told me its around a couple grand for the job or a whole new engine rebuilt..

 

At that milage you should consider an total inframe, not just rod and main bearing replacement if you plan on keeping your truck. That would include rod and main bearing replacement. Your oil pressure numbers are well within specs. . Get an oil sample tested next time you get an oil change. It will help you get an idea of internal engine wear.

 

at 900k I would stop the engine and do inframe... I had few series 60 engines and none of them reached to 900k m.