djowen

I'm getting NO hits on the brakes tech forum, thought I'd try over here:

My drivers side front brake locks ONLY when weather outside is above 80F-ish and it's been sitting in the sun. It does not start locking until I've pressed the pedal in one good time, once I've done so, they will release slightly, but I can tell my pad is touching rotor. So now the pads dragging the rotor, and continuing to drive of course heats them up further now locking the brakes, and continues locking harder and harder within a short distance.

Now for the weird thing, lets say it's a cool 50F night. I can drive for hours, with no brake problems, sure enough, the next day, during the hottest part of the day, I can only get about 5 miles into a trip before they start locking again.

Stat's and history:
This is an '89 civic DX
front disk, rear drum
I had front brakes lines replaced due to a leak 4 or 5 months ago at the dealership, they also checked the M/C and said it looked good. I replaced the rotors and pads around the same time. This was during the winter, no problems yet.
I noticed some minor problems 1ce or 2ce but not often enough to connect the hot weather. After about a month of hot weather now, I've connected the problem, testing this "hot weather theory" 30 or 40 times now during hot weather and then not again.
Took it to my local mechanic (not dealer) he wanted to replace the calipers, which he did(he also checked M/C and said it seemed to be fine). It seemed to help, (it's been a week) but then today it's blazing hot outside, and it happened again after about 5 miles of running errands.

Also wanted to add, just got off the phone with my mechanic, he thinks it could either be contaminated fluid or a bad proportioning valve.

I kinda get the feeling he doesn't believe my "hot weather theory", and I think he's fishing for old parts to replace...

any thoughts on this?

90efhatch

Sounds to me like the caliper piston is swelling when its hot and then sticking. When its colder outside it might not swell that much and not have the problem.

I would try a new/different caliper on that side and see if you still have the problem.

McGruber

Since you said you just had the calipers replaced (I'm assuming with brand new ones) I don't think they are the problem. I would have to say that fluid and the proportioning valve are a good place to start. I'm leaning more towards your prop valve due to the fact that your problem is only on one side.

djowen

cool, makes me feel a little better to hear someone agree with my mechanic, I've already poured so much money into my braking system its getting scary.

Good news is I'll be visiting him Sat morning, I'll update the post afterwards