Ok I just deleted the abs system changed my rotors and pads. I added the proportioning valve to the front brake system and have put about 75 miles of driving on it so far. My issue is it seems that I lose power brakes here and there. sometimes the pedal travels nice and smooth and stops really well, but occasionally it seems to be happening more now is the brake pedal gets stiff and I lose brake power and the car stops like s***. I bleed the crap out of the brakes and it feels great when my pedal actually travels. I read a few places is to start with the check valve. How do I test this. another theory I read somewhere that it can be a vacuum problem. Now my car is a half bridge and im pulling around 10-12 psi at idle. Im not sure what our boosters req to function proper. Any one out there that is running a halfie might be able to inform me? How rare is it for a brake booster to give out?

 

Make sure the check valve in the brake booster vacuum line is functioning. The booster rarely fails and 10-12 inches of mercury (in. Hg) should be fine for the brakes.

 

So I should remove the hose from the booster to the hard line w the c valve in it and blow compressed air through it in the vacuum direction?

 

Just blow with your mouth... it's a very sensitive check valve. To test mine, I replaced the stock hose with a hose w/o a check valve and drove with very light load (definitely no boost).

 

The valve is ok but it could be sticking. You have to blow a decent amount, a light breath it does not flow. I'll give your test a shot tomorrow. If the booster is bad it would probably be a stiff pedal all the time?

 

Sounds like the valve is the issue - it shouldn't take much effort at all for it to open.

 

Agreed.

A sticking valve would give the intermittent issues you are having.

 

The booster was removed before when I sprayed my bay down could it possibly be a bad gasket as well? I'm going to try the hose trick first.

 

Sorry I do not mean to hijack this thread But I've been curious about that check valve

My car when I brake fast after boosting , say in an auto-x My pedal is very hard , and gradually gets soft as the car goes into vacume , But I've never had an issue with braking force I've always been able to force the pedal.

My question is . well is this normal? or am I missing that check valve , and to the OP is this similar to what happens to you or does it happen reguardless of weather your car is in boost or vacume?

 

Without the check valve I believe the diaphragm inside the booster would get destroyed. The c valve is inside the hose coming off the booster to the steel line on the firewall. The valve I believe us designed to hold vacuum. Its possible your valve could be bad. I can't recall having issues after boosting tho.

 

OK did some test driving w/o the c valve just a hose and I'm still getting the same results. I did notice though when I depress the pedal lightly it feels great but when it comes to a jab its hard like a rock and stops like doo doo. I'm goon a see what happens with a hand vacuum pump to the booster.

 

Tested the booster with a hand vacuum pump and gauge and I can't pull any vacuum with or without the check valve. The most I saw was barely 5 psi and it just drops to zero.

 

Another question. I installed my proportioning valve on my front line. I'm reading that people do it this way or should it be on the rear? I'm lost cause people go both ways. I'm running OE size rotors and calipers.

 

Anyone?

 

well problem solved the booster was fine. It was my brake lines from the master that were backwards. plus moved the valve to the rear lines. I had placed the line coming from the rear of the master to my fronts and the front one to my rears. after staring at multiple pictures i found the issue. So for anyone that ever gets confused the line in the rear of the master goes to the rear brakes and the front to the front.