Main Bearing Replacement - 223

[Anonymous]

I am thinking about replacing the main bearings in my 223 - mostly due to another post I made about my rear main seal leaking even after replacement.

A couple questions:
1. Should I try the seal one more time just to make sure?

2. If I go the route of replacing the bearings, can I replace just the rear main bearing, or should I replace all the mains?

3. Any tips or special tools needed to replace them? I have a shop manual that shows a special tool, but I'm assuming that tool is out of date or unavailable. I've never done main bearings before, so any detailed advise would be appreciated. (Note: I plan on doing all of this under the car without pulling the engine or tranny)

 

[addo]

You should Plastigage the bearings to determine clearances before making any decisions. Unless one showed specific damage (at which point crank condition would be a consideration), you'd normally do the lot.

Many bearings have a source-date code on the back which will enable you to determine the year they were made, plus their brand - trivia, I know.

Oil leakage is more likely due to seal failure, excessive oil level, or excessive crankcase pressure than the increased clearance of a worn bearing. Many blocks (not sure of 223) have an oil gallery plug above the crank, near the end of the cam bore. Could that be the source of leaks?

Bearings should go into a dry (non-oily) seat; this can be hard under a car but persevere if you're doing it. The special "in-situ" tool you're thinking about, is probably the little stud which fits in an oil hole of the crank and pushes the half shell home as you spin that crank.

Have you recently done a wet/dry compression test? This might rule in or out any blow-by.

Cheers, Adam.

 

[Anonymous]

Many blocks (not sure of 223) have an oil gallery plug above the crank, near the end of the cam bore. Could that be the source of leaks?

Can I see that plug with the oil pan removed? Is it just a bolt, like a smaller version of an oil pan plug? I'll check it out when I drop the pan - assuming I can see it from that vantage point.

Thanks for the tips!

 

[addo]

No you can't see it there - it's visible on the back of your block, up near the deck. You need the block plate removed.

That is, assuming it's like the later sixes...

 

[Anonymous]

Thanks. I'll check my shop manual and see if there is any mention of it.

When I changed the main seal last time, there was no noticable wear on the rear main bearing or the crankshaft. This was just by observation and physically touching the parts - no noticable groove in the crank at the seal and the bearing in the main cap was clean and smooth and it had no extra grooving or any weird wear pattern. The bottom end itself was pretty clean. There was minimal sludge in the bottom of the oil pan and the pickup screen was clean.

I'm thinking (and hoping) that I just made a mistake installing the last rear main seal. Going through that exercise again is hopefully all I need to get it sealed up. I really don't even care if I have a slow drop. Right now, it bleeds oil at highway speeds and that's obviously a problem.