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LF Hub Heating Up

3K views 19 replies 5 participants last post by  djleblan 
#1 ·
Hi All.

I noticed yesterday that the front left hub of the car ('08 Sonata w/ ~237,000kms) is getting hot - hot enough that you do not want to leave your hand on it. I suspected the brakes were binding but when I checked them last evening the sliders moved easily, the brake caliper piston was easily pushed back into the brake caliper (with a small c-clamp) and the brake pads themselves were easy to remove without any prying tools - not much play in the carrier assembly but again easy to remove with my fingers. I am now wondering whether the wheel bearing could be starting to fail. Is it normal for the wheel bearing to heat up in this way prior to failure? I also checked for play in the tire before removing and could not feel any whatsoever (so the bearing may be failing, but there is no noticeable bearing play yet).

In this other post it appears that the temperature may be an indicator of a failing bearing:

http://www.hyundai-forums.com/nf-2006-2010-sonata/150598-bad-wheel-bearing-maybe-2006-sonata.html

Thanks.
 
#2 ·
Wheel bearing failure doesn't always show up as looseness in the bearing. Actually, it usually doesn't. Modern bearings stay tight most of the time but will be noted as being bad by making a loud noise. (****** GM wheel bearings are the exception, they always get loose and wobble when you shake the wheel)

Try this:

Put car in neutral, jack it up so you can spin LF wheel by hand. Grab onto the LF spring with one hand and rotate the tire round and round with your other hand. The spring magnifies the feeling of a rough bearing so you can tell easier. I think that if it was worn enough though that it would generate heat, you'd be hearing it on the road. Anyway, that's how you check wheel bearings nowadays.
 
#3 ·
Thanks MNV33 - we just used this method on my mother's Pontiac G5. Easy to isolate which side the bad bearing is on by feeling for vibration in the coil spring. I will give this a try on the Sonata as well. I have since removed the brake carrier and descaled it - the pads have lots of slack now so it should not be caused by them. I also removed the caliper and removed the piston to check for rust / binding. Very little rust found but cleaned everything up and piston was re-inserted with minimal finger pressure so it should no lnger be the cause either. Left front hub still appears to be heating more than right (37/27 Celsius this after commute to work this morning (LS/RS)), although it doesn't appear to be heating as much as it was before.
 
#4 ·
Hello again.

I checked the LF (and RF for comparison) coil springs as suggested by MNV33. There was no vibration whatsoever in either side. I tried it while spinning the wheel manually, and then tried it again with the engine idling and in gear (while on the lift). No vibration that I could tell with two fingers laying on the coil spring. I also listened to the hub with a mechanic's stethoscpe, thinking that I might hear some signs of bearing harshness - no such luck. Both sides of the car produced a soft sound like this - sshh, sshh, sshh, sshh - while the wheel was spinning. I think that it was likely brake pads dragging as I did not remove them for this test. I will continue to drive the car and chock the heating up to slight differences in brake pad material or rotor surface friction. I will continue to monitor for evidence of a problem - perhaps I simply caught it so soon that there isn't sufficient evidence to isolate it yet. :)

Thanks for the help.
 
#12 ·
Hi Red Raspberry.

The temperature of the tires as taken earlier this week (measured at midpoint of tire sidewall) were as follows:

LS - 38C top, 28C bottom, 58C wheel hub
RS - 34C top, 28C bottom, 44C wheel hub

As you can see, the tires appear to be similar in temperature. I suspect that the warmer tire temp at the top of the LS tire is due to the heat coming off of the hub / rotor assembly. The hub however is consistently warmer on the driver's side.

Thanks.
 
#7 ·
About a year ago,I replace pads and rotors on a car we were selling with 145,000 miles on it. In driving it,the rim itself was hot enough to the point I could not keep my hand on it for 10 seconds.Replaced the original brake hose and all was good.

If its not a bearing and your caliper is good,I would replace the hose,they are pretty cheap.
 
#9 ·
Test for collapsed brake hose:

Stab brake pedal hard with foot and then open up the bleeder on the suspect caliper.

Good brake hose will do nothing, normal dribble out of bleeder.

Collapsed hose will hold some pressure in the caliper and will squirt when you open the bleeder.

Never done that myself, but that's what I was taught. Might be worth a shot.
 
#13 ·
Hi All.

The brake hose on the LS seems like a stretch, but I will check it as described. It is possible that it has some internal resistance preventing the pressure from releasing completely. This would be an easy fix if it turns out to be the cause.

Red Raspberry, the axle nut has not been off the car while I have owned it, and that has been for the last ~180,000kms. In fact it is likely that it has not been off since installed at the factory. Is it possible for it to have tightened up over that time?

Thanks for the ideas!
 
#14 ·
Hi All.

I performed the checks suggested this morning. I pumped the brake pedal hard a few times, then loosened the bleed screw on the left front. The fluid wept out, no squirting. I repeated this procedure (including pumping the brakes again) on the right front with the same result - weeping, no squirting. These results do not support the theory that the brake hose could be failing / faulty. I also removed the cotter pin for the axle nuts and gradually worked my way up on the torque wrench from 135 ft-lbs in 5 ft-lbs increments until the nut turned under the pressure. On the left front I was at 250 ft-lbs when it first turned, and the spec is 148-207 ft-lbs, so it appears to have been too tight. I then checked the front right for comparison purposes. I was at 265 ft-lbs and the thing still hadn't turned, and I was beyond the capability of my torque wrench. I slackened both sides and re-torqued to the upper end of the range - 207 ft-lbs. Not sure why these would have been tighter than spec as they have not been off the car since installed at the factory 240,000 kms ago, at least not to my knowledge. Since the passenger side was even tighter than the driver's side, this does not appear to support the theory that the LS axle nut was too tight causing the heating. I will recheck the temperature after the next drive and see if anything has changed.

Thanks again for the ideas!
 
#15 ·
Hello agian.

I have rechecked the hub temperatures since performing the previous tests - the LS continues to be much warmer than the RS as it was before. I checked the service manual and there is nothing on a hub getting warm - all troubleshooting symptoms are listed as experienced from within the car. The only other thing that comes to mind for me is the drive axle - a failed outer CV joint could heat up but from what I have been told they generally make a lot of noise when they are bad. Is it possible that it is what is heating up and transfering that heat to the hub and rotor components? This seems unlikely. I will try to get under the car right after it has been driven and determine which component is letting off the most heat.

Thanks.
 
#17 ·
Thanks Red Raspberry. That axle has certainly seen some heat. :)

I got under the car yesterday just after driving home (~30 miles) and tried to isolate the problem further. The axle was warm on the bearing end but not on the other end and the further from the bearing end on the outside of the CV joint boot the cooler it was. The rotor and backing plate on the brake pads were cooler than the bearing area and especially the axle nut. As nearly as I can tell, the bearing is generating the heat. The following websites seem to indicate as well that a warm bearing is an early indicator that the bearing is failing...

How to Spot a Bad Wheel Hub Bearing | eBay

https://mibearings.com/page_2

I will change out the wheel bearing over the next week or two and report back.
 
#18 ·
Hello All.

I pressed-in a new front wheel bearing over the weekend. The only issue during the dismantling process was with the removal of the drive axle - it was rusted solid in the hub. I had to borrow a 14" bearing puller to force it out. The one that I pressed out did not have any obvious issues - at least not on the bearings or race that were exposed as part of the pressing out of the bearing. Everything went back together smoothly once cleaned up and lubricated. A test drive confirmed... that the bearing was not the problem. :huh: The hub is still heating as it was before - no improvement whatsoever. I noticed when I removed that caliper that it had a tighter grip on the brake pads than I would have expected - not enough to make the wheel difficult to spin but perhaps enough to generate heat on longer drives. Even though I have had it apart once already, I will remove it again and ensure that there is no rust building up beneath the seal or dust boot.

Onward and upward. :smile:
 
#20 ·
Hi All.


I resolved the issue this past weekend. As mentioned in my last post, I removed the left caliper and cleaned everything up (again) - piston seal removed and tried to remove the outer dust boot but it appears to be part of the caliper. I was unable to get it out and didn't want to tear it in the process. I did not find anything wrong so I re-assembled and re-installed it - same problem. I then wanted to rule out the pads & rotors so I took the outside pad and rotor off of the right side and put them on the left, and vice versa (I wanted to move the inside pad as well but the squealer tab interfered with the hub assembly). The result of doing this was that both sides were now warmer than expected, but exactly in the middle of the previous range and the two sides were at the same temperature. The heating problem effectively averaged itself between the two sides. This was sufficient evidence that the pads / rotors were to blame that I replaced them new and the heating problem is now gone entirely.

It is likely that I created this problem myself. :huh: A few months ago during a brake service I noticed that the pads were getting close to the wear limits so I replaced a couple of them with pads from the last brake pad change to buy myself 6 months before doing the full brake job. I would have expected those used pads to seat into the rotor after a bit of use and perform normally until worn out. This does not appear to be the case as after more than a month of driving they were still causing a heating problem. It is likely that the heating would not have caused any problems (~70 degrees Celsius at the most), but I noticed it and got it in my head that there was a problem that needed to be fixed.


MNV33, there are no noticeable heat marks (discoloration) on the rotor surface - it looks normal with the exception that there is some rust on the inner and outer 1/4 inch of pad sweep area. This could have caused some heat (I wouldn't expect much), but I believe that the pads with grooves mismatched to the grooves on the rotor are the biggest contributors to the heating problem. This is supported by the rotor without the rust (right side) still heating up when installed on the left side with the mismatched inside brake pad.


One bearing was replaced unnecessarily, but I am glad that the mystery has been solved. :smile:
 
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