Three weeks ago: After 62k, my Dodge Quad Cab gets its first new brakes…new pads and rotors up front.
Saturday: after driving about 25 miles, I smell burning, then my truck pulls to the left. Smoke billows from the left front wheel. The brakes are cooking, and car is pulling to that side. Brake seems stuck. Get it towed to mechanic.
Monday: Mechanic replaces both front calipers, rotors and some brake lines. Drives it about 10 miles, certifies it okay.
Tuesday: I take several short trips, everything seems ok.
Wednesday: About 15-17 miles into my work commute, it is de ja vous: smell, pulling, cooking of left front brake. Back to shop. Mechanix scratch their heads.
Car guys: Could we have poorly adjusted brakes…a bad booster…master cylinder???
I need to have some idea where to look, what to expect, how to reason with the mechanix.
The left front rotor looked awful both times, visible smoke/stench and the truck was fighting its brakes. To keep the fluid from boiling, I didn’t drive very far and nursed the truck to the shop today (rather than a tow job).
The most common causes of sticking disc brakes are a restricted brake hose, sticking caliper slides, and a sticking caliper piston. Presumably these have been taken care of.
Another less likely cause is a faulty brake master cylinder. Depending on the master cylinder’s design, each front brake might be on a separate circuit. If that were the case, I’d expect the circuit for the left front brake to also serve at least one of the rear brakes.
A booster problem would affect all four wheels. Disc brakes are self-adjusting (by the flexibility of the caliper piston seal) and cannot be adjusted, nor poorly adjusted.
One possibility is that the pistons were reset into the calipers without the calipers bleeders having been opened, and that this pushed some debris into the master cylinder. This doesn’t strike me as terribly likely, as it has been a standard technique for decades and I haven’t heard of it actually occurring. However, if the vehicle has ABS, debris might have gotten into some part of that system, which might more readily explain only one wheel being affected. The proper piston-resetting procedure for ABS systems is to open the bleed screw and let the fluid exit there rather than back up through the brake lines, for the very reason of avoiding such an occurrence. Assuming the rest of the job has been done properly, I would say this is the most likely explanation. If that is the case, a brake fluid flush might solve the problem (if you’re lucky), otherwise some very expensive part(s) will need to be replaced.
No. It’s an internal part of the just-replaced caliper. It’s extremely unlikely that your previous caliper suddenly went bad and the replacement is faulty.
I assume when you say “some brake lines” that the hose(s) on the left front were replaced.
There could have been an assembly error that keeps the caliper slides from working properly (assuming it has slides rather than bushings built into the caliper), but it’s unlikely (though not impossible) that such an error would have been made twice on the right side but not on the left.
To test for a master cylinder problem: When the wheel is locked up, loosen the metal line at the master cylinder that goes to the left front wheel, so that fluid leaks out of the fitting. If that alleviates the problem, the restriction must be in the master cylinder, as obviously a restriction anywhere between there and the caliper would have still kept pressure in the circuit.
If that doesn’t free it up, work from the master cylinder toward the caliper and loosen each fitting/joint in turn. When the brake unapplies, the restriction is upstream of the last fitting loosened. If the brake stays applied, the problem is not pressure retention, but must be either a faulty caliper or some sort of mechanical interference acting on the caliper.
There’s usually a return orifice in the master cylinder reservoir, which allows fluid to return to the M/C from the caliper when the brakes are “off”. If this return port gets blocked by crud, you can get exactly the situation you describe, thusly:
Brake fluid in the caliper heats up and expands theough normal application of the brakes. Normally, this expansion would be bled back into the M/C via the return port.
Port is blocked, fluid expands and has nowhere to go.
Expanded fluid forces the piston out, effectively applying the brakes.
Pads drag on the disk, heat up, smell bad, warps disk, etc.
Brakes cool off, no apparent problem.
Were the seals in the M/C replaced? It could be dirt blocking the port or a seal installed incorrectly.
I will know more tomorrow, so I’ll let you know.
The scenario of the brakes cooling off is dead on, because I was able to drive, stop, drive, stop and make it about 15-17 miles to the shop.
I think my mech still focused on calipers, although I expressed the points in here without insulting him.