Posted by WC Rick on Saturday, February 05, 2005 at 5:00AM :
In Reply to: Engine condition posted by Will (in MI) on Friday, February 04, 2005 at 8:36PM :
Will,
I agree with the others, check the crank real good where the thrust bearing runs. As far as looking for a reason why this happened, alot of mechanics have different thoughts. One thing to think of is you said it is wearing towards the front of the engine, it had a stick trans, and ever time the clutch is shove in it is pushing the crankshaft forward in the engine, putting pressure on the thrust bearing, with the forward pressure on the thrust bearing it is slowly working the oil out from between the bearing and the crank and it gets hot and starts wearing the bearing away, the oil is not pressure fed in that area, so until you let up on the clutch pedal, the crank doesn't move away from the bearing to let oil back in there to lube it, we're only talking about .005-.010 end-play on the crank to let the oil in that area, and when you have the clutch pedal down the crank moves forward and there is no clearance there now except for the layer of oil, and that slowly get squezed out, and then it is metal to metal, and the bearings start wearing. Then if you have a heavy duty pressure plate in it, it just puts that much more load on the crank thrust bearing. One thing most say not to do is sit very long with the clutch in while the engine is running, like sitting at a stop light, or in heavy traffic where you let the clutch out and move a few feet and stop again, it's always keeping constant pressure on the thrust bearing and not letting the oil in properly, always try to put it in neutral and release clutch untill light is ready to change and from time to time in the traffic. Also make sure you have the proper free-play on your clutch pedal, so it's not keeping the throw-out bearing against the pressure plate and not letting the crank move freely in that .005-.010 end-play.
Some what the same problem can happen with an automatic transmission, if the torque convertor "ballons" it put pressure on the crankshaft pushing it forwarded in the engine and continually keeps pressure on the thrust bearing, not letting oil in there and the bearing wears away. I have seen the thrust bearings completely gone and the crank rubbing on the main webs in the block, ruining the block and everything.
When motors get this bad, with the motor running you can see the harmonic balencer and lower pulley move back and forth, when someone is engageing and disengageing the clutch.
Like I said earlier, mechanics have different reasons why this happens, bad bearings, dirty oil, high mileage, low oil pressure, but if your crank is in good condition and you put in new bearings, and with proper oil pressure, you shouldn't have any problems.
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