Diesel Truck Rod and Main Bearings


I would like to talk about when you truckers should replace those rod and main bearings to make your Diesel motor last forever. Unlimited miles!

Rod and main bearings used to get replaced from around 200,000 to 3 or 400,000 miles. The diesel engine bearings and the oil we run now a days makes them last much longer. But I have been finding that a lot of or I should say most truck drivers are avoiding changing them and taking a chance that they will make it to the next overhaul. But the time in between these is also changing to record numbers.

When to change them tho is the question since every diesel motor is different and is always changing.

Here we go I am going to give you a few and see if yours falls into one of them.

Detroit diesel 60 series 6 to 800,000 miles depending if hauling rock to over the road. I have seen them spin on out anywhere between 800,000 to mil 200,000 miles I have seen overhauls last to mil 6 or 8 before needing liner o rings and usually just gets overhauled since there but I would not of been scared to just use knowledge and little cleanup time and just re seal the motor if it would have had good bearings because everything else was very reusable.

If it was mine I would have saved a few thousand and took the chance it wasn’t using oil so why change it. I have done head gaskets and not changed the Cyls’s and their still running daily With hundreds of thousands of miles more on them. The pistons hardly ever wear any at all. I have done it to a few tight truckers diesel engine and it worked great.

Cat engines are about the same mileage. The bigger the cat the longer you can go. Cat is a rpm motor to create power. The smaller the diesel engine the harder it cranks and the smaller the bearing. If your running a C 13 or smaller change them before 800,000 or else! Most motor replacements have been cat smaller engines from spinning a bearing. 8 hours labor and $200 in parts is one hell of allot cheaper than $ 10,000 Eng plus core charges in the thousands plus labor and a few bugs to work out. The bigger cats I have seen bearings out of them up to mil 400,000 and they were shot but the cat cyl’s just don’t make it they wear out from the outside and pit through and or liner o rings blow out and put coolant in the oil.

Cummins engines are the hardest on bearings they are more of a stoker diesel motor. Low end torque! This beats the bearings out but this is one of my most favorite motors to work on to make last for ever! Esp N14! N14 requires bearings every 500,000 you can go longer but the bearings look horrible and lots of brass showing. I have found the motors with this interval seem to last for ever and this is a motor that was designed like much larger motors that were make to fix one or 2 cyl’s at a time and last forever. Only reason to ever replace a block and crank is if you have a big hole in the block and it is almost imposable to do this unless you have very unusual special circumstances. L10 , M11, ISM 6 to 800,000 this motor will spin out of pushed to far. I have seen them with allot more miles but I have seen the larger percentage of these diesel engines not make it! ISX 1 mill This motor has been very good even tho its not my favorite and have had lots of complaints on HP Idling etc etc it seems to be a very low maintenance motor. ERG seems to be its only downfall. That’s a never ending expense!

Mercedes diesel this motor reminds me allot of smaller Cat diesels in the bearing department. Not many make it to mil without changing the bearings. It has very small bearings in it compared to others.

If you follow these guidelines for changing your rod and main bearings your diesel motor may out last you!

Ask trucker diesel doc.


Source by Brett Hoene

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