sticking rear brakes

[TimK]

I have experienced periodically a problem with the left rear brakes not fully retracting resulting in brake drag and overheating of the brake drum. I finally decided to try to find the cause. It turned out that the brake cylinder piston was not moving freely -- it was very tight and hard to move. There was so much friction that the brake springs were not strong enough to push it back into the wheel/brake cylinder. I sprayed it with some penetrating oil and worked it around with a screw driver until it moved very freely. It now works like it was supposed to.

 

[Scot]

Hi Tim,

Thanks for posting your solution to this problem. I also have a dragging brake on my BJ8 although I'm not sure which one yet.
While I find it, could you describe exactly how to get to the brake cylinder piston. Did you mean the brake master cylinder or something at the brake itself and also did you just use WD40 to free it up?
Thanks,

 

[Healeysince59]

If you have a sticking brake cylinder, something is wrong. Probably corrosion on the piston and/or dried up brake fluid. In either case, a cylinder rebuild is in order IMHO. Also, use nothing but brake fluid or a brake system compatible grease for lubrication.

Marv J

Note: WD40 is not a penetrating oil. WD stands for water dispersant

 

[Bob_Spidell]

I sprayed it with some penetrating oil and worked it around with a screw driver until it moved very freely. It now works like it was supposed to.

Suggest you bite the bullet and take the wheel cylinder out and find out why it stuck--could be crystallized brake fluid, rust or a damaged seal (or???). Also, the penetrating oil may have contaminated your brake fluid--not a good thing.

 

[TimK]

I meant the wheel cylinder in the left rear brake/wheel. I took the rubber cover off and sprayed penetrating oil in there, not WD40. I did not make contact with the brake fluid which is on the other side of the rubber seal on the piston.

 

[Bob_Spidell]

I meant the wheel cylinder in the left rear brake/wheel. I took the rubber cover off and sprayed penetrating oil in there, not WD40. I did not make contact with the brake fluid which is on the other side of the rubber seal on the piston.

The cylinder should have a very fine hone to allow brake fluid to lubricate the seal (original all-aluminum cylinders may not). I'd be surprised if the penetrating oil wouldn't travel through the hone channels--that's why they call it 'penetrating'--and mix with the brake fluid, or at least mix with the fluid on the seal. Also, AFAIK most penetrating oil is petroleum-based and may not play nice with the seal.

Your car, your call. If it was my car I'd want to know why the piston stuck.

 

[why]

tim: I understand you found a sticking piston so that seems most likely the problem, and if getting it loose fixed the problem great. Just in case it proves intractable, I had okay applying brakes but when letting off pedal, rear dragged. It was swelling of interior lumen of the rubber hose that connects steel brake line going to rear with the final steel line going out to wheel (rubber allowing for movement of chassis indpendent of axle), as I recall rubber hose near differential. Once all back together, loosen top of resevoir and the bleed screw on the wheel cylinder, fluid should run out by gravity feed, if it runs out,let a tablespoon or two go, then all should be okay, also would not worry about minimal contamination by penetrating fluid, I leave brake fluid in for life of regular cars, about 10 yrs no problem, and even at 20+ years in old cars at worst little ooze around seal--robust stuff.

 

[Randy Forbes]

Brake fluid absorbs the moisture in the air, and will lead to corrosion within the circuit as it condenses.

Even my lesser vehicles get annual brake fluid changes (BMW includes it during the free maintenance period__and they're frugal, when it's their money).

 

[TimK]

Thanks for all the advice. I drove down Woodward Ave. today (cruisin) and had no problems. I took a front wheel off and found that my pads were nearly gone (about 1/16th" left). The pads are the ones that came with the car in 1981. I had changed the rears and rebuilt the wheel cylinders at that time, but didn't touch the fronts. I've only put about 7,000 miles since then. I just ordered the premium ceramic pads from Moss. I've had good results with ceramics on my mini-van.