Wrist Pin Bearing Questions

satburn

satburn

New member
So I'm all excited with the arrival of my bearings only to be disappointed when I start to take the wrist pin out of the old #1 piston. It won't move. Uh oh... I take it over to the press, it comes out quasi easily but after I remove it, I find this...

Rod1Bottom.jpg


Rod1Top.jpg


:doh: Son of a... ARGH! What the? Alright, so now lets change the diagnosis from stuck injector to an attempted seize of the wrist pin, which would explain the piston wanting to smack the cylinder wall. But why? The lubraction of the top of the rod doesn't make sense to me, there's a hole in the top of the rod, but other than than that there's a cooling jet squirting oil into the cylinder. How does this thing get lubricated? A slinging effect?

Also, after I checked the other bearings, they are all brassy and all have this interesting "blemish" on them. Is this normal?

RodBearingCrack.jpg
 
It's been a while since I've seen a cummins apart, but the rod looks very similar to a deere rod that I used for a project.
As far as the top hole on the "small end" of the rod. That hole is for lubrication, and lubrication of the passive type (as you said, splash lubrication) In theory, since the wrist pin doesn't move that much, a little oil splash in there should go a long way. Looking at the wrist pin bushings, the wear on them comes from the forces of the engine. The connecting rod is forcing the piston up the cylinder against tremendous pressure and your bushings take the brunt of the force involved there.
As far as the rod bearing goes, they are worn, obviously...(you shouldn't see the copper in your engine bearings). The line in the center coincides with the oil hole in the crank, and if I were to guess I would say a small piece of trash got in there and made the "line" you're seeing in the bearing.

Just my opinions, keep in mind..:)
 
I found out the blemish is where the bearing is put together and is somewhat normal. To me this looks like a single incident that occurred prior to me. There was an obvious failure that affected the oiling of this cylinder, low oil level, debris, weak pump, etc. The kicker is that it seems to have been corrected now prior to me getting this truck but the damage was never corrected? So now what? Its a pulling truck, its going to be abused.... A LOT, so I'm a little apprehensive about just throwing new pistons and bearings in there, sprinkle some holy water on it and wish it good luck.

That oiling system for the wrist pin doesn't give me a warm and fuzzy either, if it is indeed a splash and go setup, then I can see how important that cooling jet at the bottom of the bore is, perhaps it should be renamed to "orifice of life or death"?
 
Where the bearing is put together? :confused: If that line is where the two bearing halves come together at the split of the connecting rod end, I can see why that line is there. If that line is in the small end (wrist pin end, not the connecting rod end) I would say that isn't normal since those are a 1 piece bushing that is pressed into place.
Personally, I would take the crank out of that motor and have it machined and straightened if need be. There's a reason those bearings look like they've been through a war.
As far as the wrist pin oiling situation goes, I wouldn't be worried about it. Lots of motors out there have the same method of oiling their wrist pins, and it isn't a high failure item.
 
It is the wrist pin end and yes they are a 1 piece design, but its a piece of flat metal rolled into a cylinder and the two ends joined in a jig saw shaped pattern, sort of the same way a dove tail joint in wood works. I've taken one out and you can clearly see it now, I'll snap a pic tonight. All the pics I have taken are of the wrist pin end, the rod bearings and mains all still look perfect.
 
Ah, okay..I looked at a few pictures I had here, and they looked like one continuous machined sleeve with no joint.....:)
 
Any ideas on how to press the new ones in? They are tapered and I'm not seeing how they can be easily installed using a traditional press.
 
You must log in or register to reply here.
Back
Top