How to know if a wheel cylinder is bad?
 

How can you tell if a wheel cylinder is bad for the drum brakes on the rear of my 83'? My brake warning light is still on. I replaced the master and the pedal came up after bleeding the brakes but the light is still on. Thanks.

seals...
 

Leaks tend to occur on the seals on the cylinders themselves.

Typically, when doing a brake job, you replace the cylinder seals because even if they are not leaking at present, after a flush and bleed, it would really suck to get a leak and ruin a set of shoes.

They are cheap to replace...

Good Luck...

Uh, the only way I can think of a drum cylinder being bad is if it's leaking. So I guess you could just take off the wheel and see if it's wet with brake fluid around the cylinder.

How does the vehicle stop. Does it feel like it's braking correctly? I never really put too much faith in some of those factory "warning" lights. Do the brakes feel firm when you're driving down the road and then brake? If you brake hard, do any of the rear wheels lock up?

Is it the brake warning light or is it the light that tells you one of your brake lights or tail lights are out? Your car is an '83? If you're looking at the console where the diagram of the car is and shows all the lights then that's just means one of your lights have gone out. I dunno, there's a lot of things you can check. Sorry if I wasnt' any help :D.

I appreciate everyones help. It is the light on the left of the steering wheel. It is the same light that is on when the parking brake is engaged. The pedal was going to the floor but still had slight resistance. I changed the master cylinder and bleed the brakes. The pedal came up but only around 1/2 way or slightly more. It stops ok. It just has a good amount of free play at the top (or pedal travel) before the car starts braking. I didn't notice the cylinders leaking at all. I inspected all of the brake lines and found no leaks. The only other item that I can think of would be the Brake Valve (proportioning valve). I am not sure if these go bad often plus they seem to be very difficult to find. It just seems that the pedal should be higher.

Glad it has gotten a little better. You may need to bleed again. Are you bleeding the entire system by starting at the back passenger brake, then back driver then front passenger then front driver? It doesn't have to be this but I'm just throwing this in as a diagnosis. How long have you had the car? Maybe you're just not use to the braking which may vary from car to car. It could be the proportioning valve.

When I first got my '79, the brakes where really soft and you would have to press them it down really close to the floor b4 it would start braking. It'd brake fine, but something just didn't seem right. It would have a LOT of play the first few inches and then at the bottom of the range, it would all of a sudden start braking and would be kinda touchy. I went through the entire braking system starting with the easiest thing first: bleeding the lines a few times, changed the master cylinder (these older cars are great, MC only cost $20 :D), checked proportioning valve and it was fine. FINALLY I decided to change brake booster (big black round thing up against the firewall on the driver side at the top). Took a couple of hrs but that was the problem. Now the car stops great! Sorry for being so longwinded. Basically, you may want to check the booster. :D

Thanks. I actually just got the car this week. My pedal does the same thing that yours did. It goes about halfway down before you get a good amount of resistance and it starts braking. How do you check the proportioning valve and the booster? Is the booster hard to change?

If you get into the drums and don't see any leaks then your brake shoes are out of adjustment...there is an adjusting screw I believe just below the axle...crank this out until you can just get the drum on with a little resistance from the shoes...I bet this will dramatically help the pedal height.

I will try that next. I put up a new post with all of the new found info. I hope that it helps. Here is my post just in case most are following this thread.

I went out this morning to check some items that were recommended to check. As most of you know my brake warning light has been on and my pedal was going to the floor. I changed the Master Cylinder and bled the brakes. Now the pedal it up halfway and stops ok but the pedal has too much free travel and the warning light is still on. I pulled the line to the booster and plugged it off. The brakes were much harder to stop, I had to practically stand on them to get them to stop but the Pedal started to resist all of the way from the top. However it was much harder to stop the car.
I then removed my brake warning light switch from the Proportion valve. I checked the switch and my warning would go on and off according to whether the switch was in or out so the switch works fine. I did notice in the proportion valve that when the switch is in that it is always going to be in the brake warning light on position. I read about centering the valve but I couldn't get it to budge. Shouldn't this valve go down to make the light go off and mine is all the way up and I couldn't get it to go down. Here is a picture of what it looks like. My car is an 83'. Thanks Again for everyones help. I couldn't do it without all of you.

Here is a picture of it with my sensor.

puling the vacum line to the booster will efectivly remove your POWER BRAKE function... old cars didnt used to have power brakes.. and they were heavy... it was a different world... your brakes will work without the booster... but it's hard to work it...

as for your sensor.. I'm not sure what your deal is.. but it's a pressure switch a believe... if there's not enough pressure to keep the light OFF it will go on. so the light should stay on in a FAILED state...
=as

Yes, I was just trying to see if it made a large difference. I don't know of any other way to test the booster itself. I tried to get the valve to budge but couldn't in the brake proportion valve. I am going to look at the drums this afternoon. Try adjusting them and then re-bleed just to be safe. I bled all 4 last time but you never know.

The proportioning valve is stuck, which is turning the light on, and is limiting the availability of the rear brakes. Do this:

With key on, have someone apply pressure to the brake pedal while you open either of the rear bleeders. The lamp should light up. Close the bleeder while your helper is still applying pressure to the brake pedal. Release the pedal, and apply it again. The light should go out now, and stay out. If it doesn't, then do the exact same thing with one of the front bleeders. If that doesn't solve the problem, the proportioning valve needs to be replaced.

Take care,
~Chris

wondering...
 

I was wondering when PKRWUD would chime in...

what don't you know about cars?

btw, East Coast Choppers and your garage pics inspire me every day.

First try to adjust your rear brakes then do what PKRWUD suggested (it's easy and if it works, saves you the trouble of messing with the booster). The thing about the booster is I think the only 2 places you can get another one from is Ford Dealer or a junk (salvage) yard. I had another V6 mustang that I was using for parts at the time and just took it off that one. It's really not too difficult to change. First time I ever did it took me under 2 hrs (b/c I went slow and took my time).

I didn't see this addressed, so I'll chime in. You did bench bleed the master cylinder, right?

i dont know if it has been mentioned yet but the rear tire that has the leaking cylinder will somtimes lock up. and when my booster went out i could hear it hiss when i pushed the pedal