1999 Tahoe brake issues

[damelvin]

I can't locate the problem with a low brake pedal. Everything at the wheels has been replaced, master cylinder replaced, vacuum on power booster is good, lines bled, etc. Still get a low pedal have to push to the floor almost to stop. Any ideas?

 

[Sepiroth]

Have you checked your rear brakes and wheel cylinders?

 

[damelvin]

Yes, everything at each wheel has been replaced. Even the hold down springs on the rear. I am getting no leakage anywhere. I do notice that the rear auto adjusters don't work very well, before or after they were replaced.

 

[Rivieraracing]

Could still be air somewhere in the system, some vehicles you have to bleed the calipers in a certain order, usually from the farthest back first to the closest to the master cylinder last. Try bleeding them again, might do the trick.

 

[Sepiroth]

I have heard of instances where a TECH2 or equivalent was needed to bleed the ABS system.

 

[jbdub]

Try manually adjusting the shoes out. If the shoes are not close enough to the drums, this will cause a low pedal. Adjust them out until there is some friction when pulling the drum away from the axle. Could also still be air in the system. Does the pedal feel spongy on the way down? If so you need to bleed. If the pedal goes down smoothly, and you only feel resistance when you begin to stop, then the rear brakes need to be adjusted.

 

[pincusa]

If you have air in the system, you'll be able to pump up the brakes. If you can't, then I suspect there's no air and the problem is elsewhere

 

[brodg]

take the truck to a parking lot and do a couple of panic stops activating the abs system see if this helps you could have air in the bpmv.

 

[damelvin]

Wow, thanks all for the ideas and quick response. I'll try all this weekened and post back.

 

[damelvin]

I realized I had only rebuilt wheel cylinders so I replaced them. Bled almost an entire bottle of brake fluid through the system. Adjusted rear shoes with drums off (no manual adj from the back on this Tahoe). Brake pedal comes up some but not much improvement. Any ideas?

 

[pincusa]

If you pump up the brakes, does it change? If so, you still have air in the system.

If not, I suspect you're getting blow by in your master cylinder. Maybe replace that and rebleed the whole system...

 

[damelvin]

Brakes pump up slightly. Master cylinder was the first thing I replaced when this started. I guess it's possible I got a bad one. Could the ebcm be bad?

 

[pincusa]

Just re-read your first post. Do you know if the booster is good? You might have a leak in the booster and it's not giving you any assist. This would give you the firm, but low, brake pedel feeling.

The easy way to test is to pull a vacuum on the boost and wait to see if it leaks. If it doesn't hold, then it's leaking and won't give you the assist.
You might try searching online as I know there are other ways to test it