Bad brake booster I think

[Backyardredneck]

OK my brake pedal is really hard to push.and the truck barely stops, I also have a constant hissing when the brake pedal is pushed. Is it my brake booster

[80Chevy4x4]

ok the very first thing to check is the one way valve between the engine and the brake booster....make sure air goes in one way but will not go the other way.........and make sure the vacumn line is not clogged or kinked allow air to freely flow through it.....before you condemn the booster...hope this helps.

[74 C-10 Shorty]

I've had that one way valve go out on me before, and you can here it when you push on the brake pedal..

[Backyardredneck]

Valve and hose Are good. I seriously have to almost stand on the brake pedal to slow down.Ive got nice air free fluid at all 4 corners.

[74 C-10 Shorty]

You might try these tests..

1. Turn the vehicle engine off and pump the brake pedal a few times to deplete any remaining vacuum in the power booster. Push and hold the brake pedal down with light but steady pressure. Start the engine. The brake pedal should drop slightly, indicating that the booster is working properly.

2. Allow the engine to run at idle for a minute or two. Turn the engine off and slowly pump the brake pedal five or six times. The brake pedal should stop at a higher position with each pump, indicating that the booster is not leaking and the check valve is working properly.

3. Start the engine and allow it to run at idle for a minute or two. Push and hold the brake pedal down with light but steady pressure, and turn the engine off. Continue holding the pedal down for 30 seconds or so. If the pedal does not rise it indicates that the booster is not leaking and the check valve is working properly.

[Fairlane514]

Your initial description sounds like a bad brake booster. Check valve would be more of a vacuum leak, cause engine misfire and idle issues, but the brakes may still work without all the effort you are having to exert.  Like you describe they feel like manual brakes, which means the booster is not functioning.

[454Man]

X2 booster. Been there. Stop driving...

[ehjorten]

If anyone is interested there is a guy on the 'net named Steve Gregori.  He repairs and restores GM brake boosters.  I had him rebuild and restore my Delco brake booster on my '69 Chevelle.  He Cad. plates them and he did an excellent job on mine!  When I had mine done the price was very reasonable.

www.brakeboosters.com