I got this car, because of its size. It is my 1st vehicle since my recovery from a TBI/coma that I received in a motorcycle accident.

Al of a sudden, intermittently, the brakes are engaging. While driving, the car begins to bounce. Soft at first, then with more intensity, like roling over a washboard. At first I thought it was the road I was travelling on, but then I begann to smell something and the car wouldn't coast. This prompted me to pull off to the side of the road to check the fluid. Full. The pedal would not budge, it is hard as a rock. With the car in neutral, it will not roll forward or backward.

After I let it sit for a while, 1/2 hour or more the pedal frees up and I can drive the car. Last night, I had to leave it sit overnight to release the brakes.

Anyone had this happen, or know what the issue is?

Thanks.

 

lift the car up 1 corner at a time and try spinning the wheels... more than likely a bad caliper on the front or brake cylinder on rear... if the car has been sitting for a time, parts get rusty and dont move as freely as they should...

 

87_Crown_Vic, I appreciate the reply. The issue is intermittent though and I would think that rusty parts, etc. would be a continual issue. However, the idea you had about lifting it a corner at a time next time, I'll try next time it happens to see which tire(s) locking up.

 

hard brake pedal is due to loss of vacuum assist to the brakes... but you say it locks up, which only thing i can tell is system pressurizes, and locks it up on a wheel or wheels due to parts hanging up and sticking or a hose running to the brake parts collapsing internally

 

Next time it does it, loosen the fittings on the lines to the master cylinder & let the brake fluid leak out for a few seconds & then re-tighten the fitting & see if the car will now move. If it does either the brake push rod is out of adjustment (not too likely) or the master cylinder is defective (most likely).

Replace the master cylinder. I've seen this before in those vintages of cars. What happens is the seals in the master cylinder swell up & prevents the brake fluid from being able to return to the cylinder. After sitting for a while the fluid eventually leaks past the seals back into the reservoir.

 

As the brake pedal was rock solid, with only about an inch of movement and usually requiring full body weight application and a prayer to stop, I replaced the booster. The car now requires very little effort to stop and travels/coasts very freely.
That was beautiful until I reached about 10 miles and the car started to slow. I pulled over and waited for about 10 minutes, no luck. I popped the hood and opened the master cylinder and both of the billows(?) were fully extended. I pushed them back down, replaced the top cover, started the car and it freely moved then I drove home issue free. It is however only about a mile from where I stopped so I don't know if/when it will rear it's head again.

Why would the billows(?) be fully extended in the master cylinder? The main side was only about 1/4" low, the manual says fill to it to 1/4" from the top and it was 1/2" from it. So could that 1/4" less of fluid be the culprit?

 

sounds like your master cylinder is binding up for some reason...