Extremely hot left front wheel

Post by **Eddystone** » 29 May 2022, 15:15

I'm above my daily quota of allowed questions, I know.

Hot metallic smell from left front wheel. You can feel the heat on your face about 18" away.

First assumption would be stuck caliper. Rotor didn't turn easily with trans in neutral but loosened up as you might expect it to as the piston in caliper was pressed back. If the caliper was seized, why would it free up by hand but not on road?

Nothing feels tight or loose in the wheel bearing hub assembly.

There's some play in the CV joint when rotated backwards and forwards.

Lots of Bosch brake pad left. Caliper was cleaned and lubed but now looks dry and possibly not moving freely side to side.

I'm trying to gather suggestions before I pull this whole corner of the car apart.

Perhaps most obvious thing might be a brake hose that is not allowing fluid to return out of the caliper. Hose that's there is not brand new, but looks fine.

Guess I should get a hose and replace it before getting too crazy, right?

Regarding heat: I'm assuming the heat would have to be from the pads and the rotor. Could a bad hub/bearing produce that much heat and still turn freely?

Car has 186k miles.

Post by **BlackBart** » 29 May 2022, 15:33

Eddystone wrote: ↑29 May 2022, 15:15 Lots of Bosch brake pad left. Caliper was cleaned and lubed...

Well there’s the problem - the rotor was not cleaned and lubed!

Yes, I would guess caliper. I believe there is little force normally pushing the piston back. With tools and/or force they're much easier to push.

My son’s old BMW E30 project car was getting terrible mileage on a trip, and he arrived with a front wheel hot hot. It was the caliper dragging on the rotor.

Post by **abscate** » 29 May 2022, 18:30

Stuck caliper. When they are good you can push them back in with strong fingers.
Hose failures are esoteric and get way too much press

Post by **matthew1** » 29 May 2022, 19:19

You could use a digital oven thermometer to touch different parts of the wheel, rotor, pads, and caliper to see what's hottest. If it was the hub there would be noise. I vote caliper.

Post by **kallekula** » 30 May 2022, 02:27

Binding caliper or shot wheel bearing? If you want to measure temps, buy one of those laser gun temp measurers. With it you can also diagnose a catalytic converter in seconds literally. They’re pretty cheap now. Saw that my EtekCity is now around $25 on Amazon.

Cees Klumper · Post by **Cees Klumper** » 02 Jun 2022, 06:05

Hose failures may be esoteric but it happened to me, so if you're going to be in there anyway, I would replace it if you don't know how long it's been on there. They are usually not expensive and you can't tell condition from the outside.

Post by **BlackBart** » 02 Jun 2022, 08:51

I vote yes on this, new calipers + new hoses. You have to disconnect them anyway, just replace them.

Post by **FireFox31** » 05 Jun 2022, 23:08

I always enjoy disassembling my calipers to see why they failed. Call it morbid curiosity.

Rust on the piston head is a dead giveaway. A small tear in the piston boot may be hard to find, but it's a sure sign of failure. It takes a lot for rust to hold the pad in place (against the rotor) but I've seen it happen. Post some pictures of the caliper on a bench if you can.