Brakes sticking when hot...

[Sumeronthechain]

Hey Prime,

So I am having an issue with my car and am not sure what the best plan of attack is. (1995 - 80k miles)

After pulling my car out of winter storage, I noticed the brakes are sticking.

It appears to get worse when the brakes are hot.

After a short drive with moderate braking, all 4 brakes are extremely hot, and the car is not able to be pushed by hand on a flat paved surface..

I put the car on stands and tried to spin all 4 wheels. Each one was very difficult to spin.

I did do some diagnosing. The pedal is firm, as it always has been. No mushyness when warm or cold, car on or off. The brake fluid is full and at an adequate level. When actually pressing on the brake pedal, the brakes function normal. The ABS engages and works properly. A visual inspection of the exterior of the brake master cylinder looks fine. I have not changed anything on the braking system recently.

Any ideas on what to try?


Edit: SOLVED! It was the pedal stop/sensor underneath the dash being a bit too tight.

I just recalled, one of the last things I did last fall was fix the intermittent cruise by tightening the brake switch down by the pedal(The switch tells the car to disengage the cruise when the brakes are applied). Well, the switch not only acts as a sensor, but also as the stop mechanism for the brake pedal. So, in other words when I tightened it, I must have gone too far as it was not allowing the brake pedal to full disengage, applying a slight pressure to the brakes!

A few quick turns and the brakes were back to normal. Apparently there is a very fine line between having it tight enough to trigger the sensor and loose enough to disengage the brakes.

 

[goldNSX]

Regarding that all 4 brakes getting hot it must be a central problem. So it could be related to
- brake-booster
- master cylinder
- ABS

As for the ABS I would deactivate it, release all it's pressure and test again.

Good luck!

 

[Sumeronthechain]

Hmm, by deactivate do you mean remove the fuse for it?

 

[pgilliam1]

If you loosen one of the bleeders on the calipers (do this with care - attach a drain tube if you can) is there pressure there? If the fluid comes out fast when you loosen the bleeder then the system is holding pressure - and it shouldn't. Never heard of this. Be sure to post your fix.

 

[goldNSX]

Hmm, by deactivate do you mean remove the fuse for it?

Yes, part of it but first release all it's pressure by opening a solenoid and suck part of the fluid out. If you don't know what I'm talking about send your car to a qualified mechanic because 'no brakes' is no fun either.

 

[Sumeronthechain]

Ahh I understand. I won't have much time to tinker with it this week, so I will probably take it in to a mechanic.

I would check for pressure at the bleeders on one of the calipers, but the problem only happens when the brakes are hot. Hot enough where I don't want to get anywhere near the calipers with me hands!

 

[Sumeronthechain]

Mechanic will investigate today. Will let you know what we find.

 

[Sumeronthechain]

Just got the call from the mechanic. He said he drove the car around and got the brakes warm, and there was no sticking. He also opened a bleeder to check for pressure in the lines and there was none.

Maybe it was a fluke thing? I will pick up the car tonight and see for myself.

 

[Sumeronthechain]

Well picked it up from the mechanics. Drove the car around and the brakes were sticking again.

So this appears to be an intermittent issue.

The only thing we changed on the car since last year is powder coat the wheels. But I'm think that would not cause any of these symptoms.

 

[Sumeronthechain]

Bump for solution on 1st post.

It was the brake pedal sensor/stop.

 

[goldNSX]

That's for the update. Interesting, what was wrong with the pedal stop?

 

[Sumeronthechain]

I had tightened it up just before storage last fall to fix the intermittent cruise malfunction. Apparently a bit too much.