pulsing brakes

[p24-1953]

What causes this? It only shops up at low speeds. I was wondering if I have a drum out of round? but what causes this suddenly? it wasnt there before i replaced the master cylinder and rebleed the brakes. It almost feels like a warped disk, but we all know that cant be it.

[Normspeed]

Drums can warp, but unless you heated them up a whole lot they shouldn't have done that. Any chance one of your brake shoes has been dragging and may have overheated the drum after the brake work?

Also did you clean the drum inside with brake cleaner or some other good solvent after handling? Could be some contamination on the drum. Let us know what you find.

[p24-1953]

I dont know what i could have done while bleeding them that would cause brakes to stick, and i hope that brake shop that bleed them before the master cylinder failed wouldnt have messed with any of the shoe adjustments. it would be hard to confuse a bleeder valve with the toe in out bolt

[Norm's Coupe]

I've never had pulsating brakes with drum brakes before. When that happens with disc brakes it usually means you have a bad rotor. I just had to replace the rotors on my van because they started to rust and were falling apart on the inside of the rotor. So........it's possible one of your drums has rusted to the point that it's rough now and is causing the pulsating brake. I'd pull the drums to check those before anything else. While in there, you can also check the brake shoes etc.

[TodFitch]

I've had warped drums cause pulsing in the brakes. Should only happen if the brakes got really hot or the drums were turned too much. So, as mentioned in an earlier response, check to see if the shoes were dragging as that might cause the drums to get very hot. But the only solution to a warped drum that I know of is to turn it (if there is enough material) or replace it.

You should pull the drums and have them checked for roundness, contamination or glazed areas.

[aero3113]

Maybe one of your rear drums are loose on the taperd shaft or one of the front drums is loose.

[Niel Hoback]

It might also be grease or brake fluid contaminating a shoe or two that makes it feel that way. Look for leaks.

[Don Coatney]

As has been mentioned pulsating brakes are more common with discs but a warped or out of round drum will cause pulsating in drun brakes. I was driving a 50 Plymouth last week and I noticed the drum brakes in that car would also pulsate at low speeds. The car owner and I both thought this was an out of round drum problem.

[P-12 Tommy]

I had a bad pulsating brake a few months ago. I starting pulling drums and my right front had the lining come off of one shoe. The PO had put bonded shoes on the car.

[wayfarerstranger]

what would cause the car to pull real hard to the right when braking ?? not all the time ..

[desoto1939]

i had a similar pbm on my 39 desoto. The bonded linings that are being used today are starting to glaze up and the lining gets hard sports on them. This will cause the lining to grab or become slick and the wheel will pull. When my brakes were cold this was more apparent and then when they got heated up then it went away.

I keep checking for leaking cylinders never had that pbm just the glazing effect. My mechanic has been seeing this also happening on the new cars with this newer linings.

See if you can get some old riveted linings and rivet them to your old shoes or you might have to replace with bonded linings.

Rich Hartung

desoto1939@aol.com