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Need Help With Rear Disc Brakes Locking Up, Heating Up Hot


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#1 tlocus

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Posted 21 September 2008 - 11:20 AM

Greetings,
I recently found that my rear left brakes are not releasing or staying tight. After driving a few miles (10-20) I can barely touch the rims!
It has disc brakes but also has the interior drum e-brake.
I'm gonna attempt to tackle it this morning. But any advice would be appreciated.

-could it be a sticking piston/cylinder?
-e-brake stuck on that side?
-could the fluid be clogged on that side?
-...


So far by looking at it (not taken apart yet) there doesn't seem to be any fluid leakage.

Also, after getting that hot, does that affect the brake fluid, should I flush it after repairing? And would getting this hot adversely affect the rims/tires/drums?


t
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Current Truck: 1999 Silverado 1500 Z71 Ext. Cab 5.3L V8
(Previous truck: 1991 Chevy Cheyenne 1500 W/T 4.3L V6-->Was a great truck!!)
(First car: 1973 VW Super Beetle)

#2 kdm101

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Posted 21 September 2008 - 06:14 PM

Greetings,
I recently found that my rear left brakes are not releasing or staying tight. After driving a few miles (10-20) I can barely touch the rims!
It has disc brakes but also has the interior drum e-brake.
I'm gonna attempt to tackle it this morning. But any advice would be appreciated.

-could it be a sticking piston/cylinder?
-e-brake stuck on that side?
-could the fluid be clogged on that side?
-...


So far by looking at it (not taken apart yet) there doesn't seem to be any fluid leakage.

Also, after getting that hot, does that affect the brake fluid, should I flush it after repairing? And would getting this hot adversely affect the rims/tires/drums?


t


All of the above are potential issues.

You can test the hoses pretty easily - open the bleeder screw on the affected wheel and have a helper push the pedal down. If fluid squirts out easily and under decent pressure - that line is OK. If it trickles out, then you found your culprit. Look for any crimps in the hardline on the axle from the tee connector to the caliper. If that looks good, the flex hose to the caliper could be bad. You could test that by disconnecting it and try the pedal pump method again.

For the parking brake, if the wheels freewheel when cold, then I would think it's not the problem. If you don't use it, the shoe should simply stay where it is and not cause you any issues. I'd check to see that the cables aren't tight even with the pedal disengaged or if there's a crimp in the cable tube somewhere. You can disconnect the 2 cables from the main cable under the cab. After that, you should be able to pull them back and forth in the sleeve tube easily.

On the caliper, this may be nothing more than no lubrication left (or all dried out) on the caliper slide pins. They'll bind up and cause the type of situation you're describing. I doubt the caliper piston is seizing up, but if your fluid is really old and has a lot of moisture in it, that could be the problem too.


Regardless of your problem, flushing the brake system is advised. I do mine every 2 years. I bought a pressure bleeder kit to do it since I rarely have a helper. It's been well worth the cost.
1999 Silverado LS EC SB 2WD 4.8L / 3.42 w/G80
Black over Pewter

2005 SSR 1SB 6-spd
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1972 El Camino Custom

#3 pm26

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Posted 21 September 2008 - 08:15 PM

I have seen caliper piston stick and cause problems like you describe. In fact, years ago I had a small Ford Fiesta and one of the front caliper pistons seized and caused the rotor to glow bright red from heat!

The caliper pistons will stick for several reasons:

1. accumulation of varnish like material on the piston surface due to insufficient brake fluid changes

2. corrosion of the piston chromed surface

3. deterioration of the square cut piston seal

I would remove the calipers and pop the pistons out with compressed air (unless the calipers have built-in parking brake mechanism, in which case I would just get rebuilt calipers, as these are a PITA to work on.

#4 tlocus

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Posted 22 September 2008 - 10:47 AM

Thanks for the replies.
When I dissasembled the brake removed the caliper & pads, with the e-brake off I could move the drum/assembly with ease.
After dissconecting the caliper & lines I couldn't move the piston. With the caliper lines disconnected I pumped the brakes and the fluid flowed good.
I bought a rebuilt piston for $38.99, works great now. Comparing the old and new piston, the old one wasn't leaking but looked like hell...
Also bled the entire system (went through about 2.5 bottles of brake fluid).
Bled till there was no air in line and fluid looked clean.

thanks again guys.

t

Edited by tlocus, 22 September 2008 - 11:25 AM.

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Current Truck: 1999 Silverado 1500 Z71 Ext. Cab 5.3L V8
(Previous truck: 1991 Chevy Cheyenne 1500 W/T 4.3L V6-->Was a great truck!!)
(First car: 1973 VW Super Beetle)




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