How much play in crankshaft and rod bearings is too much?

fferd

Original poster
Member
Oct 19, 2012
6
Low oil pressure while the engine is warm and idle as well as a slight tapping noise when the engine is warm led me to taking off the oil pan. From what little I know, a little play in the bearings is alright, but how much is too much?

[video=youtube_share;KImrhljpBA8]http://youtu.be/KImrhljpBA8[/video]

Two or three other bearings have almost as much play.
 

NJTB

Member
Aug 27, 2012
612
Flemington, NJ
Get a shop manual and find the specs for connecting rod side play and crankshaft/connecting rod bearing clearance. Then buy this product called Plasti gauge. It comes in a paper sleeve, looks like waxed dental floss, but 'crushes' at a known rate. There is a chart on the paper sleeve that you compare your results to.
Remove the bearing cap with the bearing in it, lay about 1/2" of the plasti guage in it length wise, put the cap back on and torque it. Remove the cap and compare it to the chart. If I remember correctly, the clearance should be 1 to 1.5 thousandths, but check the book.
The bearing caps go on one way only, DO NOT PUT THEM ON BACKWARDS OR MIX THE CAPS.
If you have too much clearance, replace the crankshaft with new bearings, and rod bearings. That's the 'proper' fix. If you're REAL lucky, you may be able to just replace the bearings. Check the crankshaft bearing surfaces for any ridges or wear, if you have none, you might be able to get away with it.
I've seen people just replace the bearings, it will run for a few minutes and sieze the engine, or run forever. A true crapshoot.

In the video, you were checking side play. Look in the manual, that's checked with a feeler gauge between the rod and the crank.

Good luck.
 

fferd

Original poster
Member
Oct 19, 2012
6
Awesome write up, thank you very much. Found the specs you are referring too.

4.2L i6
Connecting rod bearing journal clearance: 0.021-0.065 mm, 0.0008-0.0025 in
Connecting rod side clearance: 0.05-0.35 mm, 0.0019-0.0137 in
 

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