97 Tahoe Cant Diagnose Brake Problem

[kelnol]

Hi all. I have found this forum to be xtremely helpful so hopefully someone here will have input on my current problem.

At 59000 miles my Tahoe has not been too nice the last few months. In Sept we put on 4 new tires - no biggie it was time, serpentine belt, wiper sensor - told by Chevy the "campaign" was expired, brake pads and rotors. Month later the fuel pump went - ouch at $500.

Then the brakes - While driving went from fine to hard to brake, like braking with no power. First mechanic checked the brake fluid which was fine and said it HAD to be the Master cylinder. Didnt sound right but said go ahead. $300 bill paid, started the truck and pushed the brake pedal to find the same problem existed. Back in, refund of my $300 then to a new mechanic, this time told it was the Booster at $400. Okie Dokie. All was fine for a week then intermitantly (sp?) when I press the brakes they seem fine then the last 1/4 down drop off. Told by Booster guy that the Master was bad. Went back to Master guy to replace the Master they they put in that I didnt need. Within 2 miles the pedal is doing the same drop off.

Could it be that this Master is bad, the Booster is bad, or something else?

PLEASEEEEE any input!

[dbatchle]

It could be one of the calipers needs replacing. My front right caliper was not working properly and went to a specialist (who is a friend) and got the real deal. I was told all of the same.

[tableman]

Check your power steering fluid level, If it is the same system as my van the Brake booster works off of the power steering pump.

[kelnol]

Thanks for your replies.

I know that the calipers are fine and just checked steering fluid which is fine also.

Any other ideas?

[tableman]

If the Master is bad, the usual symptom is your have brakes, then while applying them and holding them on with out backing off again the peddle will fade and drop some more. When the booster is gone, you get a hard peddle but if feels like you really have to stand on it to get the truck to stop. Try this, stop your truck on steep hill, apply brakes hard and see if the peddle will fade away. If it does your master cylinder is bad. The other thing you might want to check is the adjustment of your back brakes. If they are far out of adjustment, your will have a lot of brake fluid movement,(peddle travel) before the brakes come on, but you will only notice this after a your front brakes come on first, then the peddle will have to travel just that much further to apply the back. This might be why you have a hard peddle then a little spongy before going hard again.

[Accord_boy619]

My brakes were mush, n ive replced evtin xcept the abs n booster. N ways for tableman the hydasist only came on HD burbans n HD C/K n I gues Van. Our Hoe's are vacum lines type dealy's. (dont know actual anme) I would check the calipers n wheel cylinders for any leaks. Also check for the rear bake adjustment. Oh have u tried flushin the old fluid out.

[GMMerlin]

Originally Posted by kelnol

Hi all. I have found this forum to be xtremely helpful so hopefully someone here will have input on my current problem.

At 59000 miles my Tahoe has not been too nice the last few months. In Sept we put on 4 new tires - no biggie it was time, serpentine belt, wiper sensor - told by Chevy the "campaign" was expired, brake pads and rotors. Month later the fuel pump went - ouch at $500.

Then the brakes - While driving went from fine to hard to brake, like braking with no power. First mechanic checked the brake fluid which was fine and said it HAD to be the Master cylinder. Didnt sound right but said go ahead. $300 bill paid, started the truck and pushed the brake pedal to find the same problem existed. Back in, refund of my $300 then to a new mechanic, this time told it was the Booster at $400. Okie Dokie. All was fine for a week then intermitantly (sp?) when I press the brakes they seem fine then the last 1/4 down drop off. Told by Booster guy that the Master was bad. Went back to Master guy to replace the Master they they put in that I didnt need. Within 2 miles the pedal is doing the same drop off.

Could it be that this Master is bad, the Booster is bad, or something else?

PLEASEEEEE any input!

Why are you going to 2 different mechanics to have a brake problem diagnosed and repaired?
If the pedal is hard to push (no vacum assist) you want to check the vacum source, the vacum check valve and the booster.
The pedal falling off during the last 1/4 of travel, I would check to see if there is any air in the system...Bleed the brakes completely. You may find some air in the brake lines.

[tableman]

Air in the brake line usually produces a spongy pedal, not a drop off pedal.

[GMMerlin]

Originally Posted by tableman

Air in the brake line usually produces a spongy pedal, not a drop off pedal.

It can cause both

[michaelandersonjah]

ABS Brake Modulator Valve, The thing that the black computer sits on, on that little jewel is the proportionong velve, about 120 dollars, check there, and BLEED PROPERLY; WITH THE PROPORTIONING VALVE TOOL good luck Mike