Intermittent rumble fixed, undiagnosable wheel bearing.

[uniberp]

2008 Forester 85k miles. I had an intermittent serious rumble, from the front end, that would occur typically after 10-15 minutes of highway driving at ~70mph. The brakes also vibrated badly when it happenned. It occurred about a dozen times over the past 3 months, unrelated to anything like braking, turning, changes in speed, road surface. It would self correct if I slowed or stopped for a few minutes. I checked both front knuckles, going so far as removing the axles to check for bearing play, but there was none. Even when I removed this the bearing
in the hub felt a-ok. It was only when it was pressed out (and broken into separate races and rollers) that I could see this discoloration that indicated overheating. The races show less discoloration, hardly detectable. The races are heatsunk to the axle and hubs so that makes sense, that they would stay cooler.

 

Here is what the bearing looked like:

 

 

I dipped it in thinner and wiped it off. The brown discoloration of the rollers is in the metal, does not scrape off.

 

This bearing felt fine. It was impossible to diagnose; only by disassembly (and destruction). When the axle was removed the bearing felt completely smooth. The hubs never felt hot, or even warm, to my hand, when I would pull off the road and check underneath when the rumble occurred.

 

I guess I will go back to regarding Subaru wheel bearings as maintenance replace items, good for 75k only.

A google search of "intermittent rumble subaru" turns up a bunch of similar complaints.

 

This has stressed me out for a while. Glad it's fixed.

[idosubaru]

yep, i've had them with zero symptoms as well, slightly unnerving guessing and hoping you're right!

 

plenty make it 200,000 miles without ever being replaced as well (i have 220k and 190k on my OB's and haven't had a failed bearing yet on mine), so there's no practical reason to preemptively replace them.  wheel bearings always give ample time for diagnosis and planning a repair.

 

if you replaced every part that has failed by 75,000 miles you'd have a lot of parts to replace.  but i can understand feeling good about a car too based on a past experience.

[uniberp]

Thanks. I should add that the overheating (probably) expanded the metal enough to cause interference in the very close tolerance bearing., and that started a cascading failure of friction, heat, expansion, and (quickly) eventual breakage, which would be pretty serious.

 

The road conditions here may have contributed to early failure.They are pretty beat up, and the left front ball joint needed replacement already (75k) also. I do recall that in an early snow this year, when the road was very bumpy with ice/snow patches, the vibration came occurred quickly. fortunately, speeds were lower and I was able to maintain 50mph. 

 

It would run all day at 50mph, no problem. I was wondering that because I baby this car speedwise (because I need it for my commute), if driving it harder would have stretched the bearing/knuckle sufficiently to allow more thermal expansion. I have seen bearings pressed out easily and pressed out with difficulty. It could be the difference in dirt and alignment, but it's still a difference. My machinist is a good guy, he tells me these things.

 

On another note, I'm dealing with a dragging front disc brake on my S10. The next thing I'm gonna try on that is to loosen the axle nut 1 flat.

That may give the hub enough runout to knock the pads away from the disc. Seems kinda non-precise to me, but it's old and worth a try after 2 new calipers/hose on that side.

 

 

 

 

yep, i've had them with zero symptoms as well, slightly unnerving guessing and hoping you're right!

 

plenty make it 200,000 miles without ever being replaced as well (i have 220k and 190k on my OB's and haven't had a failed bearing yet on mine), so there's no practical reason to preemptively replace them.  wheel bearings always give ample time for diagnosis and planning a repair.

 

if you replaced every part that has failed by 75,000 miles you'd have a lot of parts to replace.  but i can understand feeling good about a car too based on a past experience.

Edited January 9, 2015 by uniberp

[heartless]

On another note, I'm dealing with a dragging front disc brake on my S10. The next thing I'm gonna try on that is to loosen the axle nut 1 flat.

That may give the hub enough runout to knock the pads away from the disc. Seems kinda non-precise to me, but it's old and worth a try after 2 new calipers/hose on that side.

 

ummm, I personally would not try that, unless you really want to be doing bearings on that, too, in addition to more brake work...

 

there has to be a reason the brake is not releasing properly - if you have replaced the caliper and the rubber hose, then there may be an issue further up the line (brake line)

Does the S10 have ABS? could be something there that isnt functioning properly...

if no ABS then I would be investigating proportioning valve(s) and/or master cylinder.

[keith3267]

Are these wheel bearings serviceable, that is can they be repacked from time to time.  Every non serviceable wheel bearing I have seen so far used ball bearings instead of tapered rollers.  This would be the first for me.

[uniberp]

Are these wheel bearings serviceable, that is can they be repacked from time to time.  Every non serviceable wheel bearing I have seen so far used ball bearings instead of tapered rollers.  This would be the first for me.

 

The picture is of one half of the separated core of a sealed non-serviceable OEM Subaru wheel bearing, the same as used on pretty much all subarus 1990 to present. There were some OEM ball bearings, but they are typically replaced with rollers.

These never get repacked, you cannot get at outer side of the bearing between the hub flange and the knuckle, and if you were to force it you would risk pushing out the seal. These bearings can't be removed without destroying them. The only direction to push is outward, and there in no tooling possible that will support the inner race of the bearing while the hub is pushed outward. Installation amounts to 1st pressing in the bearing shell into the knuckle, then 2nd simply supporing the inner race while pressing in the hub from the outside.

Edited January 11, 2015 by uniberp