:beers:I have a strange brake problem not sure what it could be so here goes some things I noticed. First of all it is a 1969 Chevelle with a front disc conversion that I purchased from ground up drums in rear. The problem is the the calibers seem to be hanging or some thing else. When the car sits the front wheels are free only some light drag from the pads when you go for a short test drive and come back the front wheels are incredibly hot and over heated if you Jack the car up almost in possible to spin either front wheel? If you let it sit for a while thing cool down and seem to go back to normally. (you can spin tire again) The things I noticed is that the brakes seem sensitive when the car is running pedal travels freely then you hit a spot that seems to then apply the brakes pretty quick. The other thing is that when you start the car you can watch the break pedal go down a little the come back up. I am thinking it has some think to do with vacuum or possibly when you get on it and increase rpm that the vacuum change actually causes the brake pedal to lower and apply the breaks resulting in over heating the calipers? I could be totally off with this but not sure how to check or where to start. I have tried with a partner to raise the rpm up to 2000k with the car jacked up in the front and spin the wheels they are free with no break applied. The other thing that makes me think this could be the issues is that when you take it down the road and get on it it seems as though someone is applying the brake you can feel the car hold back. This I did noticed after I drove it a little the may have been hot and seized already though. The other thing that make me seem that it is common is that it is both front brakes are doing the same thing. Is it possible to have to much vacuum or do I have a bad power booster? Any suggestions please.

Are you still using the drum brake master cylinder? You need a disk brake master cylinder. The drum brake one does not release pressure because the springs return the shoes. The disk brake cylinder has a built in pressure release. Had the same problem when I did my front disk conversion. Took it for a test ride before I changed the M/C and almost burned up the new pads.

Nope master, booster, prop valve, Break lines were replaced with the conversion kit I orderd.

They will release when standing still cold. Had my wife in car with motor running around 2000k rpm to test could apply brake and then release. It did not happen immediately seemed like a second or two after releasing the pedal.

How about contacting Groundup and ask them where they get their kits.
Then contact the mfg. and tell them your problem.

david

Thats a idea.

I've been told this can happen if the master cylinder pushrod is adjusted too long -- the M/C piston can't retract far enough to let the fluid bleed back into the reservoir. When you drive the car and the brake fluid heats up, it expands and actually applies the brakes. This leads to more heat, more expansion, ...

There should be a bit of free play between the pushrod and the master cyl. If you drive the car and the brakes are dragging when you get back, you can try loosening the nuts that hold the master cyl to the booster -- if the brakes release after loosening the master, it's related to the pushrod adjustment...

Talked to company that put the kit together for ground up they were on the same track with this. They called it pre loading. They have me checking and possibly adjusting pedal height and 2 Making sure I have the correct push rod in there and that it is not pre loading the master when it is put on. which will do exactly that when the brakes get hot the fluid has no room to expand. It sounds promising I will have to check as soon as I can some free time over next few days.