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DCM, Auto Mechanic
Category: Car
Satisfied Customers: 680
Experience:  18 yrs Mechanic
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99 gmc: I fix or adjust (maybe diagnose..parking brake..sticking

Customer Question

How do I fix or adjust (maybe diagnose) my 99 GMC C6500 parking brake which was sticking and is now not coming on?
Submitted: 9 years ago.
Category: Car
Expert:  DCM replied 9 years ago.
Hello and thank you for using JA.

There is a few reason for the emergency brake or parking brake to get stock,

Possible reason are:

The cable is coroaded, and it's very stiff to slide back when release
: Solution, replace the cable.

Return spring is not pulling back any more:
: Solution, investigate the return spring of the parking brake, and see how it function,
if the spring is not pulling strong enough, replace the spring.

The cable is not align to the V harness of both rear brake.
: Solution, check the harness.

If the vehicle is equiped with brake shoe, check the slave cylinder, probably its not compressing back the fluid any more, and check the brake shoe return spring, could be missalign.
Customer: replied 9 years ago.
The cable looks good from my inspection. It piece where the cable pulls that is on the back of the transmission appears to be moving properly down into the transmission, maybe it is sheared off inside? Your answer sound more suited for a regular car or truck, this is a box/moving truck. The cable does not go all the way back to the rear wheels. I also checked the pink fluid in the reservoir and it appears ok. The cylinder that pulls the cable has quite a bit of rust but appears to be making its full travel and working fine. I think I have narrowed the problem down to the point where it goes into the transmission. Any advice?
Expert:  DCM replied 9 years ago.
We are not talking about air brake are we, or we are talking about hydraulics emergency brake?
Customer: replied 9 years ago.
Reply to DCM's Post: No sir not air brakes. It is hydraulic, it has a reservoir of pink liquid next to the part that pulls on the cable. (not sure what name to give that part, piston?) I read that the brakes are assisted in emergency braking situations by the power steering pump if that makes any difference. I looked a little closer at the part on the back of the transmission and it appears to be its own drake drum mounted between the trany and the drive shaft with pads and springs and such.

A couple of things happened previously...
1. Exhaust broke and was laying against the linkage on the side of transmission (no apparent visible damage)

2. Trans cooler line blew and covered underbody with trans fluid

3. The shaft of that cylinder that pulls the cable was rusting and it appeared to be pulling large rust chunks inside cylinder (cleaned that up and removed loose pieces)

4. Now when I engage the brake the cylinder pulls the cable fine, moves all linkage properly, shows "park brake" light on dash, but doesn't even attempt to hold truck still.

The truck is a 1999 GMC C6500 with 3126 Caterpillar diesel
its an under 26,000 lb truck with an 18 foot cargo box
Customer: replied 9 years ago.
Relist: No answer yet.
Not sure if he gave up or what? I need to get this fixed!
Customer: replied 9 years ago.
Relist: No answer yet.