Brake problems--maybe

[Rick Yeager]

This is an odd problem and unfortunately, I cannot be accurate in describing it. The poor car has about 70 stormy miles on it. One of the problems that I have not been able to resolve is that intermittently the car will not roll freely and resistance against the engine goes up dramatically. It will get so tight that the car will not go downhill without the clutch engaged. We think it is the brakes and are not sure that it is front or back or both. Although I guess it could be the differential. One of the things that makes it so difficult is that the problem may come and go seemingly spontaneously. It began after the car had been sitting for a long time while I was attempting my first-time body work. When we tried to push it out of the garage the brakes started becoming very tight and the car would hardly move. We stopped to rest with the back of the car pointed down hill and suddenly the car started rolling down hill freely. When the car is on the road, it generally starts out fine then gradually gets tighter and tighter and then may gradually free up. Also the intensity of the tightness may very. Stopping and backing up may make it better sometimes but not always. The brake pedaly may become very hard and hardly move at all with pressure. Also the car bucks and jerks dramatically anytime I try to back it up under power but seems to roll freely when pushed by hand. At first we thought the bucking was because the clutch had sat unused for so long but now I wonder if it is not part of the brake problem. This jerking does not seem to occur with the forward gears even when the brakes are fairly tight. Part of the problem for me to identify it or even to describe it to you is that it is frequent but not constant.

The master cylinders are the twin system with the balance bar from Shell Valley that have been out for years. The front brakes are the older Mustang II conversion ECI system which uses the 11’ Granada rotors and the GM calipers and the rear brakes are a drum system that came with the 9’ axle housing from a 1974 Mercury Montego MX. The front calipers and the rear slave cylinders have been replaced with new rebuilt units by a competent mechanic. (Obviously not me ). This did not change the problem. The emergency brake cables have been loosened to the point that they are not functional. I do not have residual pressure valves on either system. It does not have a hydraulic brake lock sysem.

I am to the point that I am thinking of asking a friend to follow me in his truck. When it occurs just pull over to the side of the road and jack it up to see if I can find something. Would any of you all have any ideas about the cause or what practical diagnostic steps I might take?

I thank you in advance for any thoughts.

Rick

[bobcowan]

Ford drums are designed to tighten (self adjust) when the brakes are applied in reverse. Also, the drums don't work as well in reverse, and tend to bind if things aren't right.

Take the rear drums apart and make sure everything moves the way it's supposed to, and it's rust free. You might also need a little grease on the backing plate where it contacts the shoes.

Also, make sure the brake rods behind the maters cylinders fully retract when the pedal is released. Had that problem with mine, and it let the front brakes drag just a tad.

[jarendall]

the GM calipers are notorious for the piston sticking, you may have to change out the O ring on the piston, to find out if the piston is stuck jack the front up and try rotating the wheels, they should turn with just a little or no resistance, some calipers use a ceramic piston, if you have these, throw them in the trash and get a set of stainless steel ones, if the problem isn't in the front brakes, you can jack up the rear, with the transmission in neutral rotate the tries to see if they will turn, if not remove the rear drums and try rotating the axle, this will tell you if the problem is in the rear brakes or the drive train, if the drums are hard to get off, then the brakes maybe to tight, once you get the drums off you can loosen up on the self adjuster
PS: since you have already changed the front calipers, I doubt that the problem is there, I also have the Shell Valley pedals and duel masters, I changed them out to Wilwood's with remote reservoirs, the pedal must be set so that their is a little slack when the pedal is completely released, if not the fluid to the calipers and wheel cylinders will not return

[Rick Parker]

Jarendall makes a very good point:

the pedal must be set so that their is a little slack when the pedal is completely released, if not the fluid to the calipers and wheel cylinders will not return

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Which calipers are you using (Metric or mid 70's Chevy)?

It is also entirely possible that the balance bar is forcing either the front or rear brakes to be partially applied.

[Rick Yeager]

Thanks for the replies. They are a great help. According to the ECI brochure, the front calipers are from a ’70-77 Camaro. It seems like a good idea to start by loosening the brake pedals. That would be a good explanation. It seems that if it were the front or rear alone, the balance bar would allow for a little play. If that does not work then Jarendall’s approach sounds like the reasonable next step.

Rick

[Rick Yeager]

As usual, I am my own worst enemy. Jarendall was really close and remembering his suggestion regarding the master cylinder may have saved us a lot of trouble shooting.

To day a friend offered to look at it. In just a few minutes on his lift he had figured that it was a fluid/pressure problem and not a caliper problem. It turned out that I had adjusted the brake light switch to close to the brake pedal and it was holding the pedal in just enough to keep the master cylinder from bleeding back. Or at least that is what probably happened. Once we turned the switch back, the problem resolved.

Thank you all for your intrest and input. I think it saved us a lot of time and trouble. This is a great forum.

Rick