Wheel bearing to replace?

MICHAEL6390

MEMBER
1997 HYUNDAI ACCENT
120,000 MILES

Hi, brakes that arent seized but wheel nuts very hot and car has lack of Power wheel bearing to replace?

Thanks

Friday, May 31st, 2013 AT 7:51 PM

5 Replies

CARADIODOC

MECHANIC
33,727 POSTS

Wheel gets hot? You DO have a brake that's not releasing. The second symptom is poor acceleration. Nothing else, including a wheel bearing, is going to cause this.

Next time this happens, stop on a slight incline, shift to neutral, place a block a few inches downhill of one wheel, then loosen the steel lines at the master cylinder. If the brake releases you have brake fluid that's contaminated with a petroleum product. That is serious. If they don't release, open the bleeder screw on the caliper that's getting hot. If they still don't release, suspect the caliper. If it does release, suspect the rubber flex hose.

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Friday, May 31st, 2013 AT 8:42 PM

MICHAEL6390

MEMBER
5 POSTS

Calipers has been changed 3 years ago. They are in good condition. I guess I should change for new brake fluid. Probably the same since 1997. Maybe contaminated
thanks

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Friday, May 31st, 2013 AT 9:07 PM

CARADIODOC

MECHANIC
33,727 POSTS

Hold on. You misunderstand my meanin'. If any hint of a petroleum product gets mixed in with brake fluid it will cause all the rubber parts to swell and become mushy. Most notably the lip seals in the master cylinder will grow and block the fluid return ports. That traps brake fluid just as if you were holding the brake pedal down with your foot Many years ago we routinely repacked front wheel bearings with axle grease, often as part of a brake job. When it came time to fill the brake fluid reservoir, the rubber bladder seal was usually pulled down and we had to pop it back into the cap. Inexperienced mechanics would thoroughly wipe their hands with a shop rag, then use their finger to push that seal back into the cap. The residue on their finger was enough to contaminate the entire hydraulic system.

Unless you know of some recent event that could have resulted in engine oil, transmission fluid, power steering fluid, or axle grease getting into the brake fluid, the contamination you have due to age is from moisture. Brake fluid loves to absorb moisture out of the air through an open cap on the reservoir and even through the porous rubber hoses. All that will do is lower the boiling point from well over 400 degrees to 212 degrees and lead to one type of brake fade. It can promote corrosion of metal parts too. All manufacturers recommend replacing the brake fluid periodically to get that moisture out but few of us actually do it. That kind of contamination is not serious and won't lead to a locked brake.

The other clue to fluid contamination is both front wheels will be affected although with a car like your one wheel will lock up first and the other one could take days or weeks more. They are on different hydraulic circuits and the two lip seals in question won't grow at the same rate.

Loosen the bleeder screw first. My guess is the rubber hose is constricted. That's the most common cause of a sticking brake. There's a metal band around the middle of the hose where rust can form and squeeze the hose closed. You'll be able to force brake fluid through the constriction with the brake pedal, but there's no pressure to push the fluid back again so it keeps the caliper applied. As heat is generated the brake fluid gets hotter and expands which applies that brake even harder. I had that happen on both of my late '80s Grand Caravans. In my case there's a bracket crimped around the hose. It takes less than five seconds to open up that crimp and fix the problem with a large flat-blade screwdriver. On most other vehicles the hose has to be replaced.

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Friday, May 31st, 2013 AT 10:15 PM

LOUIS AHLERS

MEMBER
1 POST

Good day

I've done a Hyundai Accent approx a month ago replacing both front wheel-bearings as the old ones started getting noisy and had high mileage on it.
Done many front-wheel cars front wheel-bearings over the years with no problems accept now this particular Accent.
Pirate wheel-bearings obtained and fitted to the Accent the normal and correct way it should be done and shaft nut torqued to spec and car given back to the customer. After approx one week the customer notified me there, s noise from the front wheels whereby I found the R/F wheel-bearing humming loud plus both front hubs were excessively hot.
Stripped both front hubs again but then started to look wy the new wheel-bearings overheated and failed
Bought another new set of pirate wheel-bearings but then pre-assemble the hubs on the work bench with dummy cv shafts and no brakes involved. Hubs turned but with much resistance - to much bearing pre-load found. These bearings one cannot adjust bearing pre loads as its made to have the correct pre-load once shaft get torqued-up.
Went to buy set of wheel-bearings genuine from agents and did finer measurements to see for possible size difference and to my surprise, found a 1 mm tighter bearing to bearing clearance which tightened up the pirate bearing, causing failures. One can make shims to make up the differences but its not the correct way as one buys pre determined correctly sized bearings for the purpose of correct pre-loads on the non adjustable bearings which gets torqued up.
Since then when I do especially front wheel-bearings which are not pre-load adjustable, I assemble the hub/s, fit it to the vehicle leaving the brake calipers off and running the engine and driveshaft in the air at approx 60 to 80kms/hr for say 5 to 10min then switch engine off for shafts to stop turning then feel by hand if the bearings and hubs overheat. Belief me, I found more cars with same issues where newly wheel-bearings overheats due to poor quality bearings or incorrectly tolerances.
One can make up small shims to fit between the bearings where the cones press against each other to ease the pre-loads on the rollers. I've used a few time x 2 0.3 mm shim stocks between the cones to get the bearings not to overheat.
Adjustable wheel-bearings where one can adjust the pre-loads with the shaft nut is simpler to do and any manufactured bearing thats a bit out of spec, the adjustable nut takes up the size differences unnoticed.
The pre-determined pre-load manufactured bearings where one torque the nut tight, can be a problem at times.
Its not always easy to exact work out the shim stock sizes to use But when one sits with overheating of newly fitted wheel-bearings thats of the parts rack which were supposed to fit correctly with its pre-determined pre-load torqued - its very concerning that can lead to a serious wheel-bearing seizure and possible serious car accident.
Wheel-bearings are made in mass by numerous manufactures and not always trustworthy to be flawless.

See photos below - same car, same part numbers, different makes with pre-determined pre-load sizing that differs drastically.

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