[rmajchro]

Ok, here's the situation. 1970 GTO, Power brakes, front discs, rear drums, distribution block (no prop valve), and front metering valve (all stock brake components). I just bought this car and when I firts drove it, I noticed that the front brakes felt like they were dragging. I noticed the smell of hot brakes then jacked up the front end and both tires where very very hard to turn. Started with replaceing the front hoses. Same problem. Then replaced front calipers, same problem. While the brakes were hot and locked, I jacked the car and started cracking lines to release the pressure. Nothing released the brakes. I took the front caliper bleeders out, nothing. Then I disconnected the front hoses, nothing. I had to manually colapse the the calipers to get them to release. So I replaced the calipers again. Better this time, but still when hot they start dragging. I then adjusted the rod under the dash that goes throught the fire wall in hopes that maybe the pedal is keeping some pressure on the master and it helped, but now after driving for 15-20 mins they are dragging again. I'll add that I have bleed the entire system, have new brak fluid in it, and I have disconnected the lines at the distribution block, master cycl, and front metering valve to be sure that none of those are the problem. I'm not sure where to go next. Another set of calipers? Keeping agjusting the rod under the dash?? Any comments would be appreciated! Thanks!!!!!

[PITTSBURGH 64]

Maybe the master cyl is wrong and is for an all drum set up. It would have a residual valve on the front brake port which wouldn't work for a Disc/ Drum set up.

[getmygoat]

Don't just keep buying new calipers. Obviously something is wrong and is destroying your brakes after a short time period.

I assume the brakes won't release after they get hot.

Check that your rotors are not too badly warped. All that overheating could defineity warp the rotors and this might contribute to overheating if they are warped bad enough.

Perhaps you are using the long rod between the master and booster, when you need to be using the short rod?

Here's a trouble shooting process:

(with fresh calipers) Jack the front wheels off the ground (follow proper safety guidelines).

Have a friend spin the fronts and then step on the brake. Release. See if the brakes drag. If they do, you can trouble shoot from there. (Since things are not overheated, releasing brake pressure at the trouble spot will free the brakes - versus when the system is overheated your troubleshooting efforts are not possible).

Fred

[BlueGTO]

Does your brake booster have a adjustable rod that pushes on the master cylinder that may have come loose or is out of adjustment? I know its not factory but some aftermarket ones are that way.

[4dblnkldude]

I,d put money on the fact it has to do with the rod. Adjust it as loose as it will go and tighten from there. Perhaps it is to long after other than stock components were installed. I had to hacksaw off a little bit of mine to get it to work, and theres only so many threads to adjust, so you have to die some on there with 3/8 24. good luck!

[rmajchro]

I thin it might have to due with the rod too. As I bring the rod loose, toward the drivers seat, the pedal drops. Is there anything to consider there? Also which hole is the rod suppose to be on for Power front discs? The top or bottom hole? Thanks again.

[4dblnkldude]

I cant remember which hole the rod get put into but probably the one with the straitest shot. and I know it doesnt take many threads to disengage it. How muck could the pedal drop, a half inch? I seen alot of cars at shows and so on and alot of pontiacs have different pedal heights. on stick cars especially the brake pedal is below the clutch.

[69lm69gp]

Originally Posted by rmajchro

While the brakes were hot and locked, I jacked the car and started cracking lines to release the pressure. Nothing released the brakes. I took the front caliper bleeders out, nothing. Then I disconnected the front hoses, nothing.

Unless something has changed, this tells me your problem is NOT hydraulic.

[69lm69gp]

Originally Posted by rmajchro

I had to manually colapse the the calipers to get them to release. So I replaced the calipers again. Better this time, but still when hot they start dragging.

This tell me there is somthing wrong with the clearances causing the pads to bind.

[getmygoat]

Originally Posted by 69lm69gp

This tell me there is somthing wrong with the clearances causing the pads to bind.

Yeah, but the clearances can be hosed because the caliper is overheated due to sticking brakes.

Overheated calipers can definitely seize, that's why I suggested beginning diagnostics with a set of unfrozen and unoverheated calipers.. Once the system is overheated, you can't effectively diagnose the root cause.

[69lm69gp]

Originally Posted by getmygoat

Yeah, but the clearances can be hosed because the caliper is overheated due to sticking brakes.

Yes they can. But define overheating, brakes get hot by design. Since rmajchro didn't say the rotor was glowing red or say something like "after I let the brakes cool down...". In fact he said.

While the brakes were hot and locked, I jacked the car and started cracking lines to release the pressure.

which leads me to believe the brakes where not all that hot.

rmajchro,

A couple of questions:

How bad do the brakes drag, can you spin the wheel with one hand, two hands, two people?

Overall condition of the brakes clean and freshly painted/plated or typical used car?

Did you grease the O-rings in the caliper with high temp grease?

[rmajchro]

Once they are locked, I cannot move the car in nuetral by pushing it. If I jack the car up, I can turn the wheels with 2 hands and significant force, if the the wheels are off its alomost impossilbe to turn the rotors.

I cleaned everything when I installed the new calipers. The sliders are clean and lubed. The calipers are cleaned and lubed where they make contact with the spindle bracket.

The brakes never got glowing red hot. But they do begin to smell when they are getting hot and you can start to notice the resistance as the cars drives. I'll work on it some more tonight.

[69lm69gp]

One more question, do the brakes free up after they cool down?

[jjscerbo]

See this all the time.. Check for pushrod clearance to the booster. Possably tight and not allowing the master cylinder to relax and keeping pressure in the system..

Easy to check..when the brakes are locking, loosen the M/C mounting nuts and see if that corrects the problem..

[360Rocket]

What are the chances that those are the wrong pads? maybe they are binding up because they aren't the right brake pads.