Strut bearing failure? - Type 44

[E. Roy Wendell IV]

>
>> What are the symptoms of a bad strut bearing?
>>
> Poor steering feel. Possibly some play in front end. Harsh over bumps.
> Alignment may deviate.  Higher turning effort.

Not entirely true for the type 44. There will be no play in the front  
end as the "strut bearing" is more correctly a "spring bearing". The  
only thing it does is support the weight of the car resting on the  
spring while allowing for its rotation. The strut rod is in no way  
supported by the bearing and is in fact stationary while the strut  
tube rotates around it.

The common symptom is a "boing boing" sound as you turn the steering  
wheel which is caused by the spring winding up and then releasing. By  
turning the steering wheel you rotate the strut housing , lower  
spring seat, and spring. The upper spring seat, supported by the  
bearing, should follow along but with a sticky bearing it won't until  
a significant angle difference between the top and bottom spring  
seats causes enough internal force to develop in the spring to  
overcome the drag. You might find that the steering doesn't want to  
return to center by itself after a sharp turn.

The surefire troubleshooting step is to jack the car up, take off the  
wheels, pop off the tie rods, and turn the strut by hand. The motion  
should be relatively easy and smooth. Because of the preload on the  
spring there will still be plenty of load on the bearing to show any  
faults although it is of course less load then when the car is  
sitting on the wheels. Due to the mechanical advantage of the  
steering rack, especially if the engine is running and power steering  
active, I don't think you can feel a bad bearing at the steering wheel.

I've taken apart a few very worn out bearings where there was little  
to no evidence of  grease, the balls and races were all pitted, rust  
abounded, and contamination in the form of dirt was profuse yet the  
bearing still rotated. Oddly enough, all the bearings I've taken  
apart show signs of the balls having pounded into the race with such  
force as to render it no longer smooth. Even if the bearing is  
cleaned and regreased it still won't rotate smoothly. Short of the  
spring compressing to the point that the coils stack up solid and  
transfer a huge load into the bearing I am at a loss to explain this.  
The bump stop on the strut should stop the spring from compressing to  
that point and in every type 44 front end I've taken apart so far the  
bump stops have been intact. I suspect that the design of the bearing  
itself is inadequate for the load. The balls aren't caged and there  
seems to be too few of them such that large gaps open up between  
adjacent balls. On my most recent suspension rebuild I actually added  
a couple of extra balls to each bearing and so far nothing drastic  
has happened but I have no idea yet as to whether the bearing life  
will be increased.

Dirt contamination of the bearing is often caused by poorly fitting  
dust shields that sit on top of the upper spring seat. These get  
warped over time and no longer keep dust out of the bearing area. The  
bearing itself isn't really sealed, rather the metal bits (top race,  
balls, lower race) sit inside of an upper and lower plastic case that  
snap together. The fit of the male upper housing into the female  
lower isn't all that tight. I'm only pointing this out so that you  
can consider ordering new ones along with the bearings. The strut  
boots will likely be shot as well so many times the best option is a  
complete kit.
>
>> The symptom I'm experiencing is a grinding feel and sound.  It only
>> occurs
>> during very low speed turning, as in parking the car, with the  
>> steering
>> cocked fully to the left.  Does not occure when turning right.

This doesn't seem right as a bad bearing can't really become a one  
way device i.e. it should have the same drag and therefore symptoms  
in both directions.

>> No
>> other
>> wierdness is evident yet.  The car in question is an 87 5ktq with
>> about 180k
>> miles, and the original strut bearings.

They are undoubtedly shot at this point. Like many parts on the type  
44 they seem to have a 100k life span at best.

>>
>> The part I'm talking about is part # 431412249D ... the ring shaped
>> thing
>> that is accessible only upon complete removal and disassembly of the
>> front
>> strut.  This is >not< the strut mount ... metal and rubber thing
>> secured by
>> three bolts..
>> If it is the strut bearing, what am I risking by delaying  
>> replacement?

Other than some steering system drag I don't see any safety hazard as  
long as you know about it. In any case,  none of the parts in  
question can really escape and fall off and as discussed the wheel  
will still be properly located by the suspension.

Roy Wendell
erwendell at mac.com
Too many type 44 tq
A pair of MR2s