New Guy And Old Owner Of Sierra Brake Issues

[DanielJ]

New to forum and have owned the Extended Cab Short Bed '99 GMC Sierra for many years. Well over 200K virtually trouble free miles and when purchased, it was from the "repo lot" at my Credit Union so the previous history on the truck is unknown and think luck was involved since it has been such a great vehicle.

Time to replace the air filter, plugs, anti-freeze, belts, idlers, shocks, (be aware on shock replacement if purchasing from your GMC Dealer for OEM parts, the part numbers are wrong for the '99 C/K 1500 so take in your old ones or find the PN on the units from your truck) brake pads, rotors, opted to change out front calipers (when compressing pistons, noted bubbles escaping around rubber seals) of course bleed the brakes, a process that has been successfully completed by me on other vehicles via the Motive Pressure Bleeding System.

A little embarrassed to say that it has been many years since the brake fluid was flushed on this truck. Green, dark, nasty fluid in the MBC reservoir so removed as much as possible, but noted there was still fluid left in the front part of the reservoir. Not wanting to send this gunk through the system, figured out a way to suck it out with a very small gauged tube and repeated flushing. (Have read where this fluid should never be removed from the reservoir, however, could not find a reason why not remove most of that fluid and refresh with new.)

Power bleeding completed with the Motive System and noted that the right rear clipper was very slow to bleed (painfully slow) but kept at it until clear fluid was evident. All the others were completed at the normal pace until clear fluid emerged and no air bubbles. Used a quart of DOT 3 to fill the reservoir and the bleeding process.



So now, like others have posted, pump the brakes without engine on and pedal is firm. Engine on, pedal is soft.

Air in ABS? Air in MBC?

No idiot lights stay on. Braking is good, but, hate that soft pedal feel and want to make it perfect...

Side note: Right rear caliper gets pretty hot, a lot hotter than the other calipers. Contemplating changing out that caliper and hose, but will investigate further prior to throwing more $$ at it.

Have read this post and it is interesting and am thankful to the author:
http://gmcowners.com/gmc-forum/showthread.php?t=21183&highlight=brake+bleed

Will try this process and report back, however, if others have further suggestions, would be grateful for your expertise on GMC Brake Bleeding!

A couple of pictures to complete this post:

My '99 GMC--

And a shot of the offending Right Rear Caliper:

Thanks in advance for any help you may be able to offer.

DJ

 

[Bill325]

I own a 2000 GMC Sierra, so I assume your truck and mine are essentially the same. I'm surprised that you didn't have to replace any rusted out brake lines, as I did on my truck.
Perhaps your location is easier on steel brake lines than here in Delaware. I had to replace all of the brake lines, except for the one that is attached to the rear axle. Two of my brake lines burst right in my driveway. GM has a brake line kit for these trucks, at a reasonable price. ( About $120, as I recall). The replacement lines are nylon coated for better rust prevention. I replaced one front and one rear caliper on my truck last year. Both were dragging and getting hot. The front calipers are a lot harder to work on than the rear . I suppose the reason is that the front calipers are heavier duty , since they do a lot more work than the rears. Be prepared to do battle with the front calipers !