Front Pulley / Thrust Bearings


ANYONE changing a front pulley, or loosening the front eccentric shaft bolt for ANY reason!, needs to be aware of what can go wrong with the torrington thrust bearings inside the front cover/front of engine!!

Before we wade through this FAQ, the way to prevent the problem from happening in the first place is to, (BEFORE! you loosen the bolt):

1) If the engine is in the car (this DOES NOT APPLY for 93-95's) do something to wedge the clutch pedal down -- meaning a 2x4 or something like it, holding the pedal down and wedged against steering wheel or front of the seat.

2) If the engine is out of the car, set it with the flywheel down, front pulley up, the whole time you are working on the front of the engine. Do not roll the engine horizontal until the front bolt is tightened.

3) For 93-95's you need to do something to wedge the flywheel forward - easiest we have done is a small piece of wood up through the inspection plate on the bottom of the bellhousing. With the wood between the pressure plate and the bellhousing. Do something to hold it there, because if you rotate the engine while trying to get the bolt loose, the wood will fall out.

What any of the above steps will do is to hold the rear torrington bearing in place against the thrust plate - keeping it from dropping out of place if the spacer moves forward.

Assembly 1 This is what the front "stack" looks like outside of an engine. The bolts shown hold the thrust plate and front stationary gear to the front side housing.
Assembly 2 With most of the pieces out of the way, you can see where the front torrington bearing is -- the other bearing is between the thrust plate and the front of the front gear.
Assmebly 3 Side view of the "stack" with the gear not there. For those not familiar with this assembly - it is what is setting the "end-float" of the eccentric. With the thrust plate and front gear bolted to the front side housing, and pulley tightened down, the "stack" is solid to the eccentric --EXCEPT the torrington bearings, which are floating "loose".
Loose assembly Here is the "stack" spread apart - this "group" order (front to rear) is: front counterweight, thin thrust washer (which also actually "floats"), bearing, thrust plate, bearing, thicker thrust washer, with spacer under the plate and bearings, all goes up against the shoulder on the eccentric.
Bearing and Spacer This shows the rear bearing sitting up on the spacer and against the rear thrust washer - like it should. This spacer is what the stack clamps against, and is what comes in different thicknesses so end float can be adjusted.
Bearing Dropped Here is the "bad" thing that can happen when that front bolt is loosened - there is nothing to hold the spacer in place, and it gets pulled forward when the pulley is removed. Since the bearing can't also go forward (it's against the thrust plate), it simply drops down behind the spacer.
Dropped with plate This shows the bearing dropped down out of place, between the thrust plate and the rear thrust washer.
Bearing and Spacer Bearing dropped down in relation to the spacer.
Smashed Bearing You can see what happens to the bearing when the front is reassembled, and the bolt tightened! The spacer smashes the bearing.
Bearing Side View This bearing is supposed to be FLAT!
Dented Spacer Here comes the rest of the damage--

The spacer can actually be dented by the needles of the torrington bearings.

Destroyed Thrust Plate The thrust plate gets destroyed.
Split Thrust Washer This was an extreme case - normally the thrust washer is really chewed up. This was even split!
And the resulting destruction of the thrust surface of the front stationary gear.
If you think you have dropped the bearing, you are welcome to try anything you want to get it back up in place, but we strongly suggest it will be faster to just bite the bullet, and pull the front cover off.

If you think your engine may already have the bearing down, and the engine has been run, first check to see if you have ANY end float. This is the amount the eccentric / pulley / flywheel will move front to back. Spec is .0015" to .0028" - not much at all, but some. If you have absolutely NO float, you have a problem.

All of the damage CAN be repaired with the engine in the car, and the front cover off. The front gear can even be replaced (just DO NOT rotate the eccentric AT ALL while the gear is out.

Parts list if you are going to pull your front cover:
Front cover gasket

Front cover "O"ring
Oil pan gasket
Water pump housing to engine gasket
At least one torrington bearing (assuming the front bolt has been tightened)

More parts we recommend, or you may need if it has been run:
The other torrington bearing
Front seal
Thrust washer(s)
Thrust Plate

Hopefully you will not need a front stationary gear.

If the spacer has been damaged, try to salvage it with a file or something. That way (assuming end float was previously set correctly) you will not have to re-set end float by trying various thicknesses of spacers.


Return to Main FAQ Page | Return to Mazdatrix Home Page