CM2250 764K, rod and main update!

[JMBT]

Hello, here is an update on my rod and main project progress.

A little backstory: CM2250, 764K miles. Was stock for the first 600K, always driven slow 60-62. I found Rawze's site at 300K, so from then on I did regular EGR tune ups and 15K oil changes.

I pulled the pan today expecting to see soot everywhere from the first 600K. To my surprise the inside of the motor was beautiful. No soot anywhere, only clean oil, (see attached pics).

When I pulled the oil pump it was also immaculate. So I decided do some external checks before taking it apart. The pump is clearly stamped with a #4 from the factory. Per quickserve a #4 pump should have backlash between .012-.018. Mine has only .009. The other thing is quickserve shows the drive gear shaft should protrude past the drive gear .003-.006, mine is completely flush?? I am wondering what's going on with this? Was the pump stamped wrong from the factory? It specs out for a pump stamped #2.

By the inside of the motor, I am wondering if I should even change the rods and mains, or just put it back together until a million?

My brother says put it back together and roll. What do you guys think??

Currently the coolant system is at 20psi, going to leave it for the night and see what we see tomorrow.

Other strange things: the oil pan has never been off before, it was super clean, but there was a 3" piece of zip tie in the bottom!! WTF (factory f-up??) other then that 4 very small pieces, 2 of metal and 2 that looked like sealant or something.

[Rawze]

do the rod and main bearings.

It is to prevent wrist pin wear, and when you get to a million+, if it is still going strong, you will wish that you had done it so that your not driving a ticking time bomb that could sent a piston thru the block without any warning.


IT IS A PREVENTATIVE MEASURE ... IT IS NOT BECAUSE THEY ARE WORN OUT!

Someone gotta be pretty dumb to tell you not to bother after getting the pan off it and do all that work just to put it back together, only so you can regret not doing it later on.

[Rawze]

as far as the gear pump lash goes and how it is measured, here is how the old style can be done...
https://youtu.be/8NFGLKfiEXM


the new style is a bit different from what I understand.

Also, all the gear surfaces need to be dry of oil when measuring or you will get much lower readings.

[Unilevers]

do the rods and mains, you are there anyways might as well and its a preventative measure. you dont wait for them to just wear out and then change them.

[JMBT]

Thanks for the reply Rawze. Like you said, I will probably go ahead and do all the bearings since I am in there. Now I just have to decide what to do with this pump. My oil pump looks exactly like the one in your video. I did my measurement the same as you and got a .009” reading. That would be ok if it were a #2, but it is a #4 so the idler to drive gear lash is supposed to be .012-.018” per quickserve. I will make sure the gears are dry and free of oil and try it again tomorrow.

[JMBT]

Thanks for the reply Unilevers! I think I will go ahead and do the bearings. Any ideas on the oil pump drive gear to idler gear lash problem. Or the drive gear shaft end being flush to the gear??

[Rawze]

cummins has played with different clearences with those gear pumps and with the idler gears in the gear trains for various reasons over the last few years. there are even some TSB's about it on some engines.

If I owned it, I would ensure the gear spacing was set according to the book/quickserv. If it is set too close, it has a chance of accelerated wear much more-so than it being set a bit loose. just make sure you measured it correctly.


As far as shaft end clearance, I would not adjust that one.

Be sure to pack the internals with some thick (85-140) gear oil before putting it back on so that it does not dry-start.

Be sure to replace the o-ring in the pick-up tube and to pack that o-ring with vasoline before re-assembly.

[JMBT]

Ok so I am going for it. Rods, mains, new oil pump, and piston cooling nozzles, all ordered today, will be in at Cummins tomorrow. $1700+ tax. Today I worked on sanding and prepping the oil pan for paint and cleaning the block to oil pan gasket surface. Wish me luck. I’ll give updates as I go.

[JMBT]

Oh yeah, I almost forgot. Coolant tested at 20psi overnight. I found a few external leaks, but no coolant in the motor!!