Spencer_P

I’m in the middle of doing a reseal on a 4.0 before dropping it in the Jeep. I’m at the RMS stage and given things are pretty dry and I don’t know how many years it’s been since it was last run I decided to pull the crank bearing caps to apply assembly lube. Well I removed the fifth cap and found a pretty good score in the lower bearing, crank looks decent and feels smooth. The rear main bearing looked good but I haven’t seen any others yet. I’d like some opinions on where to go from here.
I assume I’d need to remove the crankshaft to do both lower and upper bearings? At that point probably do connecting rod bearings as well?
Thanks in advance!

bluejeep2001

Thats not so bad, looks like the bearings took a bigger hit than the crank itself. Some crocus cloth or scotchbright might do a good job smoothing out the journals..don't look like they have to be cut. If you got it that far apart might as well do the rods also. When mine got eaten, the silver of the bearings were worn all the way down to copper color. Since it looks like the motor is on a stand...do it all

Spencer_P

The rear main bearing looks similar to 1 and 2 with no visible score. Every other bearing has a score.

bluejeep2001

In the jeep world, they're pretty clean...buff them out and just replace bearings. After you buff out the journals..wipe the bearings clean and throw some plastigauge in there to check your clearances bet you can reorder same size bearings that you have now...lets see what the rod bearings look like

Spencer_P

I’m not worried about the journals at all. I’ll try to get the clearances measured and the fresh RMS removed and crankshaft out tomorrow. . I’ll read through the FSM tonight and see what I can find.
I’m thinking I may order a new oil pump as well. I was told the engine has 70k on it but now I’m seeing some stuff that may suggest otherwise.

Ricthewrench

I am in the "buy once cry once" camp on bearings. And oil pumps. 👍

Spencer_P

I read something yesterday is the FSM about connecting rod position when measuring rod bearing clearance and I thought I took a picture of the page but I don’t see it. Is there a certain position they need to be in when measuring? I think it said to rotate until the rod starts to move upward?

Spencer_P

Here it is

Spencer_P

Plastgage results
Crank bearing clearance
RM-7: .002"
6: .002"
5: .002"
4: .002"
3: .002"
2: .002"
1: .002"

Connecting rod bearing clearance
1: .002"
2: <.002"
3: .002"
4: .002"
5: .002"
6: <.002"

The connecting rod bearings are marked .001" on the backside.
If I'm correct I think these measurements mean I'm good to order standard size bearings for both crank and rod?

bluejeep2001

The manual calls for bearing clearances of .001-.003 so exactly the same as you took off would work. I am not sure if they are stamped .001 means .001 tighter than stock for undersized journals (worn) or .001 looser than stock for repaired cranks that might be bigger than stock..if there is such a thing?

5-Speed

There is normally an X stamped on the bearing if its +.001 extra clearance. I am willing to bet these are for a worn crank, which also means someone has already been in this guys engine.

Spencer_P

… I believe they said something along the lines of “.001” 4-99x JA95”.
Given that it’s a 99 engine I was hoping that meant they were original 99 bearings…
I ordered standard, guess I’ll be exchanging them

5-Speed

Can you post pictures of the back of the bearing with all the numbers? To me it sounds like it isnt a stock bearing at all.

Jim Malcolm

Google is indicating that it was common practice for them to mix-match bearing sizes to account for tolerance during manufacturing. You can get 0.001 undersized rod bearings on Rock Auto, but not main bearings.

Spencer_P

I will take pictures when I remove the crankshaft this weekend. The FSM states that the sizes were not marked on production engines.