Okay, so this is a used car that I bought a few years back and had an obvious brake problem, turned out the front right caliper was definitely not releasing. Replaced the rotors, bearings, calipers, pads, and brake hoses inside the wheel well, on both sides.
I have not used the car much since then because problems have persisted. Here are the symptoms I’m seeing. When I get up to 45+ (esp. going downhill), I start getting wobble in the steering wheel. After driving for 10 or 15 minutes, I usually (but not always) start to get a wheel/rotational squeak that goes away when I brake. The front brakes seem too hot: just got home from a short drive and both the front rotors were at 400+ degrees (F).
I’ve posted about some of this before, but I think I’m describing the situation more clearly now. To me it seems like both front calipers are keeping too much pressure on the rotors. What could do that? I looked for a pinched brake line and didn’t find anything. Power brake booster? Hydraulic control unit?
Oh I should mention that I took out the fuse for the ABS a while back and it made no difference. And the rear brakes seem okay to me, that is they are not getting too hot or otherwise attracting my attention.
And when this happens, the hoses can act like check valves,
This means when you apply the brakes, the hydraulic pressure forces the pistons out. But when you release the brakes the hoses prevent that hydraulic pressure from being released. So the brakes stay applied.
Sounds reasonable. I did pull the fuse for ABS, but I could also unplug its wire harness.
I’ve wondered if some valve in the ABS or hydralic control unit got stuck. Of if maybe there was some other malfunction/contamination in there. Causing it to act like a check valve, as you mentioned with the hoses above.
After driving for 15 minutes, jack up the front of the vehicle. Do you feel heavy drag when rotating the front wheels? Loosen the master cylinder mounting nuts and pull the master 1/4" away from the brake booster to see if the front brakes release.
Take a look at the MC. Does it have rubber brake lines between the MC and the proportioning valve? Not a common configuration these days, but my older Ford truck is configured like that. If your Explorer is like that, one of those rubber hoses could be the problem, would likely affect both front brakes.
My guess however matches up to Nevada’s above, not enough play between brake pedal and brake MC, causes the brakes to be applied slightly all the time. If so, ask your shop if it might be possible to fix that problem without replacing the MC.
The front brake drums on my Ford truck could be called the hub, b/c they contain both inner and outer wheel bearing races. There are two tapered wheel bearings that are separate parts, easily removed from the drum. According to Tester’s link above, seems some 94 Explorers are configured w/separate tapered wheel bearings, some are configured with the type of wheel bearing that is pressed into the hub, sealed wheel bearings like used on bicycles.
Just curious, OP says in top post title their Explorer is XL 4WD. Is that the same as what you refer to as all wheel drive? So it uses the type of wheel bearing that is pressed into the hub, which I’m assuming is also the disc?
