Alec

I just changed the oil in my work truck, and discovered "something" in the oil pan. Put a bar next to the clutch fork & slid the crank forward a good quarter inch. It seems pretty clear that the thrust bearing has fallen apart. I am pretty sure that it has been this way for at least 5k, if not 10k or more, based on clutch disengagement height.

The deal is that I have a new project truck from AZ that I am trying to strip & give a serious rustproofing rebuild (adding drain/discharge holes, re-sealing seams, adding polyethelene splash guards), and don't have enough time to get that project going, let alone do it & put a bunch of effort into my daily driver that I have mostly given up on due to body & chassis rot . . .

So, who has some good first hand experience with running these engines with a broken bearing, or replacing the bearing in the truck. I remember Monty said he had to pull the engine up until the front of the crank was at the top of the grill, and Aaron ended up pulling his engine -- but no one has talked about this for a while as far as I can tell, and I was wondering if anybody had some insight or tricks.

Thanks!

Alec

wannadiesel

I don't have any practical advice beyond replace it, don't just keep running it. Once you get the pan down it's not a hard job.

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JD730

I have a perfectly good John Deere 404 engine here with a similar failure, thrust bearing fell out, crank rode on the block and spun all 7 main bearing by riding them on the fillet. Could have been prevented if the guy checked the bearings when they were switching engines like I had suggested.

I've never pulled the pan out of a 1st gen while in the truck, but I've done it in a 2nd gen more than once. Had to pick the engine up as high as it will go, drop the pan down, then drop the oil pickup tube into the pan. Taking the pan down is easy, putting it back on because of the limited room to get the pickup tube back on is difficult.

apwatson50

I had the same failure, probably had 5k on the failed bearing. I ended up just pulling the engine, putting it on the stand so I could change bearings standing up. By the time you have everything unhooked to get the engine up high enough to get the pan out I figured it would be just as easy to pull it all the way.

So I did and replaced all the bearings, rods and mains, then shoved the engine back in. Been running since for ~30k miles. No known issues.

I definitely wouldn't keep driving it now though!

oh also immediately disconnect the clutch safety switch and do not start the engine with the clutch disengaged EVER!! This is the main reason, IMO, for the failure.

Alec

Well, I'll have to roll some bearings in. I can't believe that I haven't had catastrophic failure yet . . .

Hopefully I'll be able to get the pan off with the engine in the truck -- things don't come apart & go together so well after ten years of being soaked in road salt.

Thanks for the info.

Alec

Alec

To remove the engine pan in a 4 wheel drive chassis:

Remove the fan shroud, fan, & fanclutch. Drain the radiator. Disconnect the intake hose @ the turbo, the aftercooler hose elbow @ the turbo, the aftercooler hose at the intake horn (if so equipped), the exhaust pipe at the turbo, the exhaust hanger at the bellhousing, the upper radiator hose at the radiator, and the lower radiator hose at the engine. Remove the nuts on the engine mounts under the crossmember. Remove the nuts holding the transmission to it's mounting plate. Unless you have a significant suspension lift, raise the front of the truck by the frame until the front axle reaches full droop. Raise the engine by the front lifting eye until the engine mount studs clear the crossmember. Jack up the transmission about 3/4 of an inch, and slide the engine & transmission assembly forward about an inch. Raise the front of the engine another until there is about an inch between the bottom of the engine mount studs & the top of the crossmember (while paying attention to the bellhousing contacting the seam in the cab).

Jacking up the transmission gives you more room to get the pan back under the flywheel housing, and sliding the assembly forward gives you more room for the clutch housing to come up under the cab, and the head to tip back toward the firewall. With the top of the intake manifold in plane with the top of the radiator support, I had plenty of room to slide the pan in and out.

The wear surface on the thrust shell lying in the bottom of the pan didn't even look broken in. I rolled out the old number six top shell using a pencil in the oil passage, and rolled in a new Clevite shell. There were a couple of little burrs in the fillet that I rubbed off with an india stone, but otherwise everything looked pretty good. I only replaced the number six bearing. The crank had been pushing forward with the fillets wearing into the rear of the bearing shells, and the wear had been getting deeper over time. I was only a few thousands away from the edge of the thrust surface on the crank rubbing on the edge of the relief that the thrust bearing surface fits into. I think if the crank had made it that far forward it would have been serious regrind/remanufacture time.

I also found two piston cooling nozzles in the pan, number 2 & number 4. Unfortunately, you cannot install them with the crank in the block. I thought I might be able to slide them up through the oil passage and into their bore in the block, but their bore is not in line with the passage. I can't believe that Cummins messed up on the thrust bearing & PLASTIC cooling nozzles. The rest of the bottom end looked like it was ready for a million miles easy.

Installing the oil pickup tube is very easy. It lies in the pan nicely, and it was easy to keep the gasket surface clean. There is very little clearance between it & the pan, so reaching into the pan to attach it before installing the pan is no problem.

Sorry no pics of taking the pan off, but it was a disaster getting dripped on and with jacks & lift in the way etc. and I was over at my friend's place, which is much nicer than my garage, but no place to run inside & get cleaned up for a minute, etc. I'll try to post some pics of the bearing shell & nozzles.

Yeah, getting dripped on and installing 36 screws while lying in a puddle of oil . . . that's most of the job.

Exekiel69

This is a common problem with the 4bt, the crank trust bearing comes apart and falls in the pan. This is more of a problem on engines with a manual transmission behind them. Cummins did come with a part to fix this, You have to call and specify what You need (the updated bearing not the old 3 piece bearing) since many cummins counter person do not know this.

Here are a few pics from the one I got for My 4bt but the problems seems to be the same on early cummins 6bt as well.
Now changing just the one bearing will fix the problem with the crank riding in the block but a new bearing with a set of used one on the crank will provably cause a drop in oil pressure or could starve it. The advise I received was to order a bearing kit and replace them all for which You might a well to a engine refresh (mild rebuild) since You will need to pull the engine anyways.
If at all possible do not run it in this condition.
Just My .02c.

Alec

So, the old number six main bearing:



The thrust face that fell off (very, little wear -- not even so much as the other face):



And the "quality" cooling nozzles. These must have been simply forced out through their bores during a cold weather start:

Alec

By the way, the pictures that Exekiel69 posted are of the OLD STYLE main bearing. You can see that the thrust faces are attached to the shell with three dove-tailed tabs. The new bearings are a single u-shaped piece.

d22019

What is the downside to running one with missing cooling nozzles?

j_martin

Nuthin major, just blown pistons.

Exekiel69

Yep thank You for clarifying that, after more than one hour on the phone with the cummins tech I still got the wrong bearing. There is a member on a 4bt forum a frequent who is a authorized cummins dealer and sells a complete kit for this particular repair and saves the aggravation from calling Your local cummins dealer and get someone who is ignorant of their own parts.
The way I was told if You have to do this repair might as well pull the engine and replaced all the main bearings and while at it check everything else that might need work in the future such a broken/fallen piston nozzles.

d22019

That's what I thought, melted pistons. I just wanted some clarification because Ive seem a few posts on different forums were guys tear apart the engine and find the nozzles in the pan. They claim no damage but who knows, maybe if its a bone stock grocery getter.

Alec

Well, the engine still runs, and runs well, even. I'm turned up more than you might think -- the advanced timing really heats up the pistons.

So, in theory, I am MUCH more worried about running without the nozzles than I am about mis-matched crank bearings. (The new bearing having a thinner oil film/wedge, etc. and all the wear from the fillets riding on the bores, etc.) The only thing is, I bet the nozzles have been gone for 50k miles or more -- years ago the oil pressure crept down a little on the dash gauge, so I put a mechanical gauge on to check & was still within spec. . . . but in hindsight, it could have been a nozzle coming out.

You can bet that I will try to take care of these problems in any future builds!

'Mad Max'

howdy folks. So, I'm about to start on my conversion, the donor truck has about 240 on the clock - runs and drives good - but while the engine is out I am planning to replace the main bearings while it's all apart. Eventually I'll do a full overhaul, but for now I just want to cure the KTB and KDP (Killer Thrust Bearing and Killer Dowel Pin).

While the engine is on the stand my plan is to rotate it upside down, pull the main caps, raise the crank out of the block about an inch or so (still connected to the rods), swap the main bearings for fresh ones, slather on some break-in lube, lay the crank back in, and put the caps back on, and button it all back up. Nothing else.

Sound about right?