M278 ENGINE ROD BEARING PLAY AFTER TORQUING.
Thread Starter
Newbie
Joined: Jul 2021
Posts: 14
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From: Sacramento, California
2012 S550
M278 ENGINE ROD BEARING PLAY AFTER TORQUING.
Hello all, I'm in the middle of rebuilding my M278 engine of a 2012 S550. I got the rod bearing and did torque to spec after replacing the bolts and the bearings ( 5NM then 25 NM then 90Degree)I noticed after that some of the rods do play and others don't so I don't know if it is normal or not ? Any help will be appreciated . Thank you.
Out Of Control!!
Joined: Sep 2018
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From: unbegrenzt
2017 GLE350 4MATIC
Maybe @arsupisemnet can comment.
Junior Member
Joined: Nov 2019
Posts: 19
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From: SC
07 S550, 99 Q45t, 89 Mirage Turbo
Get some plastigauge, put a strip on the bearing material, torque to spec then remove. Measure the diameter with the provided gauge to find out what the bearing clearance is. Do this to all of them and look up what the specification is in the FSM. If it is excessive, you may need oversized bearings.
Super Member
Joined: Jul 2019
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From: New Orleans
2014 GL450, 1992 W140 300SD, 1993 W140 300SE, 1987 E30 Convertible
There is no oversize (repair) bearings, at least official ones. However there are a color coding on bearings diameter. Normally each bearing pair in this engine is manually fitted for machining play and encoded on the crankshaft - there are some letters you might see like r-g-g-r and so on.
In your case get yourself plastigage. You would need the one with green color. If your clearance is around or less than 0.002 inch you are ok.
In general you use assembly lube, and there is a play along crankshaft axis - since these are free floating connecting rods.
In your case get yourself plastigage. You would need the one with green color. If your clearance is around or less than 0.002 inch you are ok.
In general you use assembly lube, and there is a play along crankshaft axis - since these are free floating connecting rods.
