Vacuum Booster

ebcjlc · January 1, 2008

I have a 92 blazer, 350 TBI, I replaced the brake booster and Master cylinder in it. Upon doing so, everytime you step on the brake the engine revs up and then when you let off the brakes it does it again. The pedal will go down the floor (not easily) when the truck is on but not when it is off. I have bleed the brakes..... no air in the system. I repaced the new booster (Reman) immediately and the issue is still there.

Zembonez · January 1, 2008

I have a 92 blazer, 350 TBI, I replaced the brake booster and Master cylinder in it. Upon doing so, everytime you step on the brake the engine revs up and then when you let off the brakes it does it again. The pedal will go down the floor (not easily) when the truck is on but not when it is off. I have bleed the brakes..... no air in the system. I repaced the new booster (Reman) immediately and the issue is still there.

Let me qualify my guess with this: If your vehicle is equipped with a check valve in the main vacuum line, it may have failed. It is a one way valve that keeps vacuum constant on the booster side. I am not certain if your truck has one or not...

If so... You should be able to blow through it one way and not the other. If is isn't working, the engine has to supply full vacuum every time the brake is used instead of relying on the reserve supply in the booster.

ebcjlc · January 2, 2008

I have a 92 blazer, 350 TBI, I replaced the brake booster and Master cylinder in it. Upon doing so, everytime you step on the brake the engine revs up and then when you let off the brakes it does it again. The pedal will go down the floor (not easily) when the truck is on but not when it is off. I have bleed the brakes..... no air in the system. I repaced the new booster (Reman) immediately and the issue is still there.

The Check valve is working correctly.

Zembonez · January 2, 2008

The Check valve is working correctly.

It is possible that the rebuilt booster is bypassing internally. Im afraid I can't offer up much more of a solution.

Good Luck!

ebcjlc · January 2, 2008

I have a 92 blazer, 350 TBI, I replaced the brake booster and Master cylinder in it. Upon doing so, everytime you step on the brake the engine revs up and then when you let off the brakes it does it again. The pedal will go down the floor (not easily) when the truck is on but not when it is off. I have bleed the brakes..... no air in the system. I repaced the new booster (Reman) immediately and the issue is still there.

The Check valve is working correctly.

That is what I am afraid of also.... wouldn't be the first time I have had New Reman parts be bad from the store a couple of times in a row. Boosters just suck to put in. Have it down to ten minutes but it is still a pain.

Thanks

hubbycap · January 2, 2008

I have a 92 blazer, 350 TBI, I replaced the brake booster and Master cylinder in it. Upon doing so, everytime you step on the brake the engine revs up and then when you let off the brakes it does it again. The pedal will go down the floor (not easily) when the truck is on but not when it is off. I have bleed the brakes..... no air in the system. I repaced the new booster (Reman) immediately and the issue is still there.

The Check valve is working correctly.

That is what I am afraid of also.... wouldn't be the first time I have had New Reman parts be bad from the store a couple of times in a row. Boosters just suck to put in. Have it down to ten minutes but it is still a pain.

Man, 3 R+Rs! Those pinched up nuts fight you for every thread. I feel the pain.

Zembonez · January 2, 2008

I have a 92 blazer, 350 TBI, I replaced the brake booster and Master cylinder in it. Upon doing so, everytime you step on the brake the engine revs up and then when you let off the brakes it does it again. The pedal will go down the floor (not easily) when the truck is on but not when it is off. I have bleed the brakes..... no air in the system. I repaced the new booster (Reman) immediately and the issue is still there.

The Check valve is working correctly.

That is what I am afraid of also.... wouldn't be the first time I have had New Reman parts be bad from the store a couple of times in a row. Boosters just suck to put in. Have it down to ten minutes but it is still a pain.

Man, 3 R+Rs! Those pinched up nuts fight you for every thread. I feel the pain.

Recently I stopped off at my local parts store for some stuff and there was a guy in the parking lot installing a booster on an older Ford pickup. I spoke to him and we got to talking. He said he was installing his third reman booster that day on that very truck so he brought his tools and was doing it in the parking lot! Apparently it isn't too uncommon to get a bad one.

That sucks!