brakes

Hi All,

I have a 1991 C1500 chevy pickup with a 5.7L engine. Here's my problem, I haven't had the truck for very long and when I got it I had to fix some engine problems. I've gotten those taken care of and now I seem to have a brake problem. The brake pedal is spongy, and if the vehicle is running and I put the brakes on, the engine idles up higher. Almost like there is a vacuum leak. I have bleed the brakes several times, and if I don't start the truck they pedal stays firm. But the minute I start the truck up, it's back to spongy pedal again.

Any ideas,
Bob

Check for a leak at the vacuum booster behind the master cylinder fo a vacuum leak

I had the EXACT same problem. Check your rear brakes. Mine had the self adjusters installed wrong by the previous owner. I had to change the wheel cyl because they were leaking, got all new springs for the whole works, and adjusted self adjusters until the shoes dragged and then backed them off a little. Great firm feel now. let us know how it turns out.

joe92k1500
I was going to tell him that also untill I read that his idle goes up when he hits the brakes. So what you want him to look at would have nothing to do with a high idle with the brakes on. He has a vacuum leak someware in the brake booster system. The big vacuum line coming from the booster is sucking air or the booster its self.
I had 1 that when the owner put the truck in gear the idle would go up and when put back in park the idle returned to normal all because of a bad brake booster vacuum line. When it was put in gear the engine would rock to 1 side(bad motor mount) and pull the vacuum line and cause a high idle.

FirePlug
I thought the same thing on mine ( 92 k1500)because, I had the idle increase while pressing the brake. I took care of the drums first just because , well, they weren't really working, and once i droped the truck off the stands and took it for a spin to test the brakes, the idle problem went away. I checked all the booster hoses for leaks anyway because i was thinking the same thing you were. I didn't find any at all. All hoses were tight and in good shape. Six months later still fine. I really didn't think that woud rectify the idle problem , but it hasn't come back. That being said, you're absolutely right in checking for vac leaks, but just for grins i would also take a look at the drums. Just my :2cents: Later.

WOW thats odd but its good you got it fixed

WOW thats odd but its good you got it fixed
I 'm a die hard chevy driver. I have a 98 c/k 1500 e-cab 4x4, 5.7 v, silverrado.
The first thing i noticed about this truck was the lack of brakeing power.
as a home wrencher i was taken back when i noticed the small brake calipers in relation to the 6,640 pound curb weight of the truck,not to menchin the thought of loading up the truck with fire would and driving down the mountain.
I have looked around for an up grade kit for this truck ,,,$$$ 700.00 plus and many kit's in the low Grands.
Ho hum ,,,it looks good sitting in the drive way. glen.