- This topic has 13 replies, 9 voices, and was last updated 9 years, 2 months ago by
.
-
Topic
-
Hello all,
I have a 1972 cutlass with all drum brakes. I don’t drive it very often as my roof is rusting through. I was going drive it to a body shop to see if they could fix the roof issues but when I used the brakes, the pedal went to the floor and the red brake light came on and I was barely able to stop. So this weekend I first bled the brakes. It didn’t help so I trouble shot the pads and the calipers. The pads were not worn and the calipers were not leaking. I checked the lines for any damage and there was none. So I checked the booster and it holds pressure and responds to the vacuum of the engine. So I replaced the master cylinder and bled the brakes again. It now has better stopping power but still feels weak. I tried locking up the brakes but I couldn’t. Is there any thing I’m missing. I also braked in reverse and pressed the parking brake in case they need to be adjusted. Do I need to check something else? Or are my brakes just not very good?
-
Replies
-
I am confused… You stated that they are drum brakes all around… Yet you also said you inspected the calipers and pads… Do you have disc in the front?
Bleed it. Bleed it. Bleed it. I can’t tell you how many times I’ve seen spongy brake pedal and it just needs to be bled.
Sorry for my incorrect terminology. By calipers I meant wheel cylinders and by pads I meant brake shoes. I tried to accelerate then slam on the brakes to see if it would get stiffer/better but the car wouldn’t lock up at all and it didn’t change the braking power. As far as bleeding goes, I’ve bled it three times since I put the new master cylinder on. Thats why I’m stumped. I suppose I could bleed them again. No harm in it right.
Check the wheel cylinders. Altrough they are not leaking there could still be a problem. Notice if they are properly positioned when you take the drum off. Is one side retracted more than the other? I’ve had a wheel cylinder not going back all the way to its original position when depressing the brakes, causing the drum ot overheat and giving me the spongy brake pedal symptom. You may not have driven the car enough to heat the drums, but with a failing cylinder the brake pedal would be exactly like you describe it.
You say you don’t drive the car often. How long has it been sitting? Is it stored outside, does it sit on grass for long periods of time?
The brake system is one of the first things to rot out on cars that spend most of their time sitting around, especially on an unpaved surface. You could have a leak anywhere in the system. You’ll need to get under the car with a good flashlight and trace every inch of every brake line, looking for signs of wetness.
Having said that, you may not have fluid leak at all. Another likely culprit could be the flex hoses. If they are old, cracked and brittle, there’s a good chance they’ve been passing moisture from atmosphere into the brake fluid. Brake fluid has a high affinity to liquid and vapor water, and will absorb it through the tiniest of imperfections over time. If your brake fluid is contaminated with water, you’ll never get a firm pedal. You’ll need to drain, refill and bleed the entire system, as well as replace the flex lines.
I checked the wheel cylinders and I didn’t see any problems. None were stuck and both sides operated the same. I checked the brakes lines, especially the rubber tubing, and I didn’t see any moisture. But there may be a micro leak somewhere I cannot see. I did replace all the fluid in the lines when I replaced the master cylinder. But I haven’t replaced the flex hose ever so it may be letting some moisture in somewhere. I’ll change the hoses just to see if that improves anything.
I remember Eric having a similar problem with a spongy pedal in the PIF minivan and he repeated the bleed with the engine running to resolve the issue; maybe give that a try.
It might not be a bad idea to replace all four (4) brake cylinders when changing the flexible lines at each wheel.
Have you adjusted all the drum brakes per the video which only shows the rear
but would be the same procedure for all 4[quote=”72Cutlass442″ post=147808]I checked the wheel cylinders and I didn’t see any problems. None were stuck and both sides operated the same. I checked the brakes lines, especially the rubber tubing, and I didn’t see any moisture. But there may be a micro leak somewhere I cannot see. I did replace all the fluid in the lines when I replaced the master cylinder. But I haven’t replaced the flex hose ever so it may be letting some moisture in somewhere. I’ll change the hoses just to see if that improves anything.[/quote]
1. If there was a leak in one of the brake lines it should show up when bleeding as the line will continue to draw in air when you bleed and you will never get an air free fluid flow out of the brake nipple into the bleed tube.
2. Did you properly bleed the new master cylinder when you installed it.. You never mentioned if you did. If not it will still have air trapped.
Evil-i is spot on for replacing all the break fluid. Go buy two quarts of new dot3 and do that. Such a hugely important thing that people overlook! When you started this adventure, was there any brake fluid in the resivior? Was it clear like water, or was it not translucent? If you can’t see thru brake fluid, that’s a strong indicator that it’s contaminated with atmospheric moisture and is starting to rust the hard lines from the inside out. That is a for sure sign to flush all the old fluid out and run fresh new fluid through all the lines.
Most gm drum brakes for a very long time have an auto adjust feature. Go to a large, empty parking lot, go backwards at 20ish mph, them slam on the.brakes. if they make a ratcheting sound, that is the auto adjustment happening.
Also, pull off the drums and look at the shoes for signs of glazing. Get a few cans of brake parts spray cleaner and spray them down and the inside of the drums too.
The brake fluid in the old master cylinder was clean before I replaced it. I haven’t tried to adjust the brakes like that so I think I’ll give that a try.
I bled the brakes properly and bled until there was no air at all coming out of the lines. And I think I went through three of the medium sized containers just to be sure. However I may not have bench bled the master cylinder correctly as I only did it for about 5 mins. I watch a youtube video of a guy bleeding one like mine and he said it could take up to 30 mins of constant pumping to get all the air out of it. I’ll have to.check that out as well. And the wheel cylinders are not too expensive so I might just replace all of them if I still have problems.
- You must be logged in to reply to this topic.