zee28

My 99 Silverado 1500 with 115k miles had a serious issue with the brakes today. After being parked, I started it up and the pedal went all the way to the floor. Minimal ability to stop the truck. I thought I blew a hydraulic hose because I thought I saw a puddle in the driveway where it was parked, but when I got it home...to my surprise...it wasn't really that low on fluid in the master cylinder.

The pedal still goes right to the floor with minimal effort and there is a noticeable "huffing" sound coming from the booster. What gives? I have not heard of a brake booster failing but that is what I am guessing. Any guidance would be appreciated.

Jay

golfer

If you have the Hydra-boost and not the vacum assist checklowpower steering fluid.

astroDZak

To test the booster simply pump off the vacuum until you don't hear it as you pump then hold down the pedal and start the truck. The pedal must drop enough you can definately feel it under your foot or the booster is faulty.

zee28

Guys thanks for the replies. I don't know about Hydra-boost but the power steering fluid was not low. With the truck parked and not even started, the brake pedal goes just about (within an inch or so) to the floor with minimal resistance. You can't pump it up...it's not holding pressure. When you start the truck, that minimal resistance goes away and the pedal goes easily to the floor with no resistance.

I have what looks to be some fluid leakage along the drivers side frame rail under the cab, but again the level in the master cylinder is not low.

I don't get it???

astroDZak

Hydra boost brakes have lines from the power steering pump to the booster and were used mostly on diesels. Vacuum boostis shapedlike a salad bowl with a lid on it laying on its side and has a vacuum hose from the intake.
Your booster is working or the pedal would not drop further when you start the truck. There is a possibility something has come apart in the rear brakes but I kinda doubt it.
Make sure your master cylinder is full and that there are no oil spots under the vehicle then pump the brakes and hold then pump and hold again a few times then look for oil spots. Also watch the back side of the rear tires incase it might be a blown wheel cylinder.
If you don't find any leaks then bleed the master cylinder and try again. There is a possibility the master cylinder is bypassing inside and only working on the front brakes. If you don't get a good amount of fluid after bleeding the master a few times then I would suspect it.

golfer

Some gas powered vehicles used the Hydra-boost system as was the case with my 2000 Express van.

If you have the vacuum assisted power brakes try this :

With the engine stopped , exhaust the vacuum in the lines by depressing the brake pedal several times.

While holding firm foot pressure on the brake pedal ,start the engine ,the pedal should move downward when the engine starts. If it doesn't check for vacuum leaks at the inlet hose ... should be the same as engine vacuum.
With the engine stopped the vacuum should remain in the line.

Some of the vacuum lines may have a check valve that may be faulty.