Moose2

I have a '66 Olds Starfire (425 ci) and the brakes lock up (all 4 corners) after driving it 10-15 miles. When its only run a few miles the brakes seem fine and aren't binding. I took off the rear drums and they come right off (cold) so I don't think the e-brake is binding and failing to release. My problem is that I want to try replacing the master brake cylinder, and I have the screw-on top on mine so I think its a Bendix. The only replacement master cylinder I can find is the Moraine style with the snap-on spring clamp. Can I put the Moraine master cylinder on my car without any problems? I'm too dumb to know and I sure could use some feedback please!

MDchanic

You should be able to, but your symptoms are not those of a bad master cylinder.

When was the last time you changed your brake hoses?

Brakes failing to release (usually at only one wheel or axle, but there's no law about that) is often caused by the inner layer of the brake hoses swelling and creating a "check valve" effect, where fluid under very high pressure from the pedal can go into the cylinders, but it cannot return under the light pressure of the shoe return springs.

Take your car for a long drive, then jack up all 4 wheels right away when you get home and open ONE brake bleeder. If the wheel you opened relaxes its pressure, but all the others stay tight, there's your problem (note that one hose goes to both rear wheels, so opening rear bleeder should release BOTH rear wheels).

I had considered this to be a problem most characteristic of '50's and '60's era German cars, but I recently saw it on a 2002 Dodge van. In your case, it your car has the original hoses, that would be a strong argument for hose swelling as the culprit.

If you DO change the hoses, while you've got everything apart, and have damaged a number of brake lines, you may wish to consider installing a dual circuit master cylinder.

- Eric

Moose2

Thanks for the thoughtful reply and I'll give it a try. However I'm not sure about the diagnosis yet. I put the car on the freeway when the brakes had not been asked to perform, and it will travel at road speed for 10-15 miles before the engine starts to labor and strain to maintain road speed. When the car is on the surface streets prior to putting it on the freeway you can approach a stop sign and bump it up into neutral when you are coasting at a walk, and the car continues to coast without any hint that it is being dragged down by brakes that are engaged..... I will be replacing every brake line on the car within the week, but I'm not sure the brakes are failing to release because it acts very normal on short runs of less than 5-10 miles.... Anything useful in what I'm saying here???

Moose2

Hey I forgot to mention, this is definitely all 4 corners of the car, not just the rears and not just a wheel here or there. And when the car is cold I can take off the rear road wheels and the drums come right off without a struggle at all, so whatever is happening when the car is at road speed is releasing after it cools off. This problem is so bad that when it happens it makes the engine overheat and if you pull over the car binds down to a halt, and if you put it back in gear (either forward or reverse) you can run the engine up to 2,500 or 3,000 rpm and it won't defeat the bound up brakes. The car just rises on its suspension and is obviously fighting the brakes without moving at all. I need all the help I can get!!

Moose2

Another thought while I'm at it; the shop manual tells me that if the brake pedal is not a correct distance from the floor-pan it can cause the brakes to drag and bind. I plan to check and adjust, but in your opinion would that cause the kind of problem I'm describing where the amount of drag and resistance is only evident at road speed and is so fierce the engine can't defeat the binding brakes? I won't bug you with any further questions. Thanks for your patience!

oldcutlass

Do you have power brakes?? I'm assuming you do! Is there a proprtioning valve in there somewhere, or a distribution block?? There may be crud caught up in your system causing the check valve effect as mentioned above, but it has to be somewhere before the system seperates in all 4 directions. I don't believe a hose at 1 of your wheels will lock up all 4 wheels!

I would check all your lines, junction blocks, and proportioning valve, for damage, and run a fluid transfusion by thoroughly bleeding each wheel till you get fresh fluid to them!

oldcutlass

Well I was typing my input as you were adding to the symptoms. Look to see if your some of the brake system is running near your exhaust. Possibly one of the retainers has broken loose causing the line to come close and heat up!

MDchanic

He'd have to have all three hoses bad, which I have seen on cars of this vintage that have been sitting.

As for the rest of it, poor fluid return, by whatever means, combined with heat from highway-speed friction could do this.
If the drums turn completely free when cold, then it's GOT to be a fluid return problem, as it CAN'T be the shoes being adjusted too tight.

I've never heard of a bad master keeping pressure on the brakes when it shouldn't but the brake pedal adjustment idea is another possibility, IF the brake pedal was messed with recently. A properly adjusted pedal wouldn't just suddenly become misadjusted, but if there were recent changes, then the pushrod could be too long, causing the master to always be slightly depressed, possibly causing this problem - The only problem with this theory is that I would expect it to make the shoes tight in the drums as well, but maybe not...

- Eric

Moose2

Thanks guys; and you both gave me good feedback. I just got the car two weeks ago so I'm still learning what has been fiddled with recently and what hasn't. The car has 87,000 miles (actual) and it has obviously been sitting for some time before I bought it, so it's quite possible the sitting has caused some problems. They threw a new exhaust system on it, and stopped at the rear of the mufflers, which point directly at the reat axle from a distance of about 8-10 inches. I thought that might have been the problem and put downturns on the mufflers to deflect at least some of the heat until I can sort out this problem and make a date with Midas (or equivalent).

AZ455

So you don't even need to touch the brakes for them to begin to lock up?

I was thinking maybe push rod out of adjustment or incorrectly installed in the booster causing a preload of the booster/MC.

Moose2

You are so right!! You do not have to touch the brakes and they'll begin to lock up. Would checking the distance of the brake pedal from the floorpan tell me if the push rod was out of adjustment? If I examine the booster assembly closely I might be able to tell if it has been unbolted recently, but otherwise, how could the booster possibly be installed wrong to cause my problem??

MDchanic

Okay, not to sound like a wise guy, but are you telling me that you can get out of your driveway and onto the highway without touching your brakes ONCE? Not even to hold the pedal down while you shift into gear?

I'm skeptical.

- Eric

AZ455

Next time the brakes are locked up, try loosening the connection between the booster and the MC, if the brakes release its likely internal binding inside the vacuum booster.

If the pushrod is too long it'll close off the vent ports in the MC and not allow pressure to be released.

This page talks about pushrod adjustment some...

http://www.cardone.com/english/club/...s/93039354.asp

Sorry I couldn't find something better at the moment, gotta goto work!

Moose2

Don't worry; you're not being a wise guy! I have to touch the brakes as you mention and now that I'm trying to diagnose the problem, I try to be as gentle as I possibly can and not stab the pedal hard or ride the brakes. I try to time myself if I see a red light ahead so that I get off the gas way back and let the car coast down a bunch and/or give the light time to change so I don't have to stop. there are only three lights between me and the freeway, and like I said, the car shows no signs of binding brakes (that I can detect) before I get 'er on the on-ramp. You gave me an idea; I can start if from cold and just drive it through a couple of stop/go situations and take it back while the brakes aren't smokin' hot and take off a rear drum immediately to see if they're starting to bind on the drum but just haven't locked the car up yet. It might tell me if the hydraulics are pushing the shoes against the drums by whether or not the drums still come off freely or I have to fight with them after I drive it a couple of miles. Sound dumb? Thanks for your patience Eric.

Moose2

Thank you AZ455, I'll check it out!!

Moose2

I figured it out thanks to a lot of good feedback from you guys. The car sat too long without being driven and the slave cylinders weren't releasing. I'll rebuild the whole system, including the master cylinder, all lines, slaves and shoes, so I oughta have brakes when I'm done........ Many thanks guys.