What would cause brakes to stick?

[Welby]

My Limited has vacuum conversion, and I've been having loads of brake problems. I've bled the master cylinder and all of the brakes, but they still feel lousy, and the brakes stick. By sticking I mean, if I'm at a light with my foot on the brakes, when I let off the pedal, the car won't move and the pedal stays down. I actually have to put my foot under the pedal and pull up on it, then the car will start coasting. I can feel them drag alot too.
The brakes were already converted when I bought it, and was told everything was new. The front calipers/rotors and rear drums/shoes do look pretty much brand new.
Would a bad master cylinder cause them to not release like that??

 

[gofstbuick]

Is the pedal rod centered and adjusted properly? Is there 2 holes on the brake pedal? If so, the upper hole is for manual brakes and the lower hole is for power assisted brakes.

 

[Welby]

not sure, I'll have to look later on tonight. Between this and the whining steering which I still need to fix, it's annoying to even drive it

 

[wagon]

Maybe the front hoses have collapsed. This can cause the front brakes to hang up.

 

[BarnesGN]

I have seen a bent slide pin cause sticking ( on a honda).

 

[gn4u2c]

yeah if they are cheepo hoses or old ones swap them out. I had that problem on the Monte . Yes they use the vac brakes and the same hoses so it's a better refrence anyway.
Good Luck

 

[Welby]

Is the pedal rod centered and adjusted properly? Is there 2 holes on the brake pedal? If so, the upper hole is for manual brakes and the lower hole is for power assisted brakes.

There are two holes, and it's setup on the lower one. Everything seems centered OK. I don't hear any air leaks under the dash. I just ordered a TTA vacuum block (A previous owner hacked it into the PCV valve), and I'm going to get a Goodrich stainless brakeline set from Summit. I'll see if these things help any. If not I'll move on to the master cylinder... *shrug*

Thanks guys....

Mark

 

[bruce]

My Limited has vacuum conversion, and I've been having loads of brake problems. I've bled the master cylinder and all of the brakes, but they still feel lousy, and the brakes stick. By sticking I mean, if I'm at a light with my foot on the brakes, when I let off the pedal, the car won't move and the pedal stays down. I actually have to put my foot under the pedal and pull up on it, then the car will start coasting. I can feel them drag alot too.

Something just isn't releasing.
Try putting the car up on jacks, then apply the brakes, and one by one loosen the bleeder valves. If one *burps* fluid then the brake line is acting like a check valve. If any wheel is just plain hard to spin, then a caliper is sticking. If one rotor looks like it's been hotter then the other, the one that looks like it's been hotter probably has been.

There is the one in a million case of the combo valve going bad. ie not releasing the pressure in the rear brakes to release.

 

[WFO_SS]

contaminated brake fluid can also cause the brakes to act weird. sometimes the pedal might be soft, and sometimes hard. sometimes it feels like the brakes are always on and sometimes it feels like they won't stop the vehicle. if the rubber on the bottom of your reservoir cap is swollen or the fluid appears swirled/seperated, the fluid is contamintated. the most common cause of this is mixing regular brake fluid (dot3) with synthetic (dot5.)
a bent caliper pin & the brake hoses are also two common causes. raise the front wheels & make sure they spin fairly freely by hand. have a friend apply the brakes while you crack open each bleeder on the front brakes. the same amount of fluid should come out of both (relatively.) after you close the bleeder and release the pedal, make sure the wheel spins.

 

[Welby]

Well, I got my TTA Vacuum block on and replaced the front brake hoses with new stock replacements. If anything, the problem got a little worse . The dragging is really noticable, and the car is actually difficult to drive.
I jacked up all the wheels and pumped the brakes with the car off. The front brakes were completely stuck. The back were fine. When I started the car and pumped the brakes, they would release OK. I did notice when the car was running, if I would bring the rpms up to 2,500 or so and let off of the gas, I could see the brake pedal pull itself down a little on its own. Is that normal?

Thanks again for any tips.

Mark

 

[John Larkin]

The front calipers are "quick-take-up" design. Meaning they retract farther than normal to reduce or eliminate brake drag, enhancing fuel economy. If yours are not performing properly, they may need replacement. As cheap as they are, I would replace them.

 

[Gbodynutt]

Welby, you said the brake pedal actually sticks down after you release it? Any idea what vacuum booster was put on there? How much vacuum is the engine pulling at idle? 2500 rpm's?
The hoses and calipers can cause the brakes to stick but that is normally that wheel or sometimes both, i've never seen that cause the actual brake pedal to stick also. Sounds to me like something is not allowing it to release properly. Either there's a problem with the master cyl., booster, or pedal rod assembly. IMHO.

 

[Welby]

No idea what booster is on it, since I bought the car with it converted already. At idle, I have about 15lbs, and dropping down from 2,500 or so it hits 20lbs. The weird thing to me is, when I do take it to 2,500 or so and let off, the brake pedal starts to apply itself

 

[Gbodynutt]

Hmmm... it actually starts to apply itself?!?!? Almost sounds like the booster is causing the problem. Anyway you can get one to try out or would you have to buy new?