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MG MGA - Brake problem II

Glenn and Jeff, thank you for your help. Here's where I'm at now....
I pulled the drum off the front passenger side wheel. All looked ok to me. (the "untrained eye")The springs were in place, I measured about 5/32" of lining on the shoes, no shiny or uneven areas on the linings or drum. I had my daughter press the brake pedal while I watched. The left cylinder and shoe operated what I would think is normal. The cylinder opened and the shoe moved outward toward the drum. The right cylinder didn't move at all, as a result, the shoe didn't either. This is where I'm at now. I guess I could have a bad cylinder or a plug in the line going to the cylinder.
Should I pull off the small tubing running from the brake hose connection at the left cylinder and check for good fluid flow, then rpleace the right cylinder if the flow is good?
Sorry to keep the questions up, I've already learned more about the braking system today than I've learned in the past 60 years.
Appreciate any and all advice.
Jerry
Jerry Murphy

Hi Jerry. First off, your brake shoes are considerably worn, and should likely be replaced. 5/32" is getting pretty thin. (particularly so if the friction material is riveted to the shoes) In regard to your hydraulic problem, it sounds like the non moving wheel cylinder is probably seized. The fact that the one cylinder moves and returns alright, and the other one does not, would indicate a seized cylinder. It could be possible to have a plugged metal line, but this is rather unlikely. A plugged or deteriorated rubber flex hose also seems unlikely, since the "good" wheel cylinder moves and retracts as pressure is applied and then released. It sounds like the brake return springs are in good condition, so that seems to infer a problem with the non moving wheel cylinder. Seized wheel cylinders are quite common, particularly with cars that have been in storage. This is because the wheel cylinders are cast aluminum, but the pistons are steel. This combination of "different" metals causes a white, powdery corrosion to build up inside the cylinders. Usually wheel cylinders on stored vehicles are badly corroded and pitted inside, and often CANNOT be safely rebuilt. Such pitted cylinders will usually leak profusely after being rebuilt. I would remove the brake shoes, and try to move the (bad?) piston by hand. In unseized condition, the piston should pull out of the bore relatively easy, using hand pressure only. If it wont budge, it is seized and the wheel cylinder will then likely need to be replaced. You could dismantle the wheel cylinder and see if it is free of corrosion and pitting. If so, you could attempt rebuilding it. If it is corroded and pitted than chuck it and get a new one. Hope this helps! GLenn
Glenn

Jerry,
It has been a while since I did my brakes, but I believe the left or rearmost cylinder on the passenger side should operate the top brake shoe, and the right or frontmost cylinder should opperate the bottom shoe. If you hold the top shoe so it can't move, does the bottom one move when the brakes are pressed? Does it return freely? If it moves without binding when you hold the top shoe, it could just be that the rear return spring is weak or has lost its temper. The springs are supposed to be equal strength. If the bottom shoe does not move and return freely when you are holding the top shoe fixed, then it could be a blockage or kink in pipe, but more likely would be a corroded cylinder. If you can't find any external reason for it binding, I would disassemble the cylinder and check for binding and corrosion. Brakes are not something to guess at. If you find any corrosion, I would check or replace all the cylinders. How long has it been since the last time your brakes were rebuilt, and how often do you change your brake fluid?

Jeff
Jeff Schultz

When you press the brakes with the drum removed, often only one cylinder will move if the other is a bit sticky. This is not necessarily a big problem as with the drum in place the first cylinder will press against the drum and there will be more pressure to move the other.

Generally what I do is to use a G clamp held in place to stop one cylinder from moving and get someone to gently press the brakes to check whether the other cylinder is really stuck or otherwise free it up.
Dan Smithers

I was about to write what Dan did. Just pull the drums 1 at a time that way the chance of popping a cyl apart is less. On the rears with only one cyl. it is easy but on the fronts you must hold one cyl to check the other.
Goob luck Randy
R J Brown

No time to look at the car for a few days guys. Youngest daughter is off to college Thursday so we're helping with the big move. Will keep you posted on my progress and will likely have more questions when I get back at it.Meanwhile I have new brake shoes for the front wheels and a wheel cylinder ordered. I sure do appreciate your help.
Cheers, Jerry
Jerry Murphy

This thread was discussed between 16/08/2005 and 17/08/2005

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