Boost leak? or worse?

[JLMazzella]

Ahh thanks alot for the info, much appreciated.

[JLMazzella]

So i got the pressure tester, and started doing some tests. I turned the pressure regulator on my tank to about 20psi (i gradually increased im not dumb) and it was leaking so bad that the pressure tester was reading 9 LOL. i fixed a few leaks (stock BOV, couple of hose clamps and vacuum lines) now it reads about 11. i get in the car and notice the same wooshing sound that i thought was the rear turbo (we got that fixed and it wasnt the cuplrit). Upon further inspection its the vacuum booster (im not sure exactly what it does but i know it has something to do with the brakes and maybe some other things). when u press the brakes in and out the tester psi surges up to match whatever i have my regulator set at, and the wooshing sound goes away.

But heres the kicker. we pinched the line going to it (assuming if no air is getting to it how can it leak) and the pressure tester was reading up to 18 without any leaks) but when we got in the car with it pinched and took it for a test drive, it still wont boost past 9psi regardless of MBC setting. What is the deal? bad mbc? tommorrow morning im gonna take it off and run a modified stock set up and see if i can at least get to the stock setting of 12.

BTW i do not recommend driving the car if uve pinched the line unless u have ALOT of straight road and no traffic, slowing from 40-50 mph with hardly any brakes is scary and dangerous. We were as safe as humanly possible while doing this.

[syangvr4]

You got bad vaccum check valve. I had the same problem go buy new check valve and put them in between the plenum and the brake booster. you might also want to check your clutch vaccum also. theres a check valve for both of these.

[JLMazzella]

Thanks ill give that a try later today.

[phantomrt]

Originally Posted by syangvr4

You got bad vaccum check valve. I had the same problem go buy new check valve and put them in between the plenum and the brake booster. you might also want to check your clutch vaccum also. theres a check valve for both of these.

Bad check valve(s), or the clutch booster hose is installed backwards. The check valve is in the hose that exits the drivers side of the plenum. I had no idea it was there, either.

I had this problem, too and I figured it out only by trying to find out why my clutch booster wasn't working. The clutch booster must also be able to bleed off boost pressure on its own...which is why you hear the boost leak sound so close to the firewall and on the drivers' side.

[etecnifibre]

Originally Posted by syangvr4

You got bad vaccum check valve. I had the same problem go buy new check valve and put them in between the plenum and the brake booster. you might also want to check your clutch vaccum also. theres a check valve for both of these.

Originally Posted by phantomrt

Bad check valve(s), or the clutch booster hose is installed backwards. The check valve is in the hose that exits the drivers side of the plenum. I had no idea it was there, either.

I had this problem, too and I figured it out only by trying to find out why my clutch booster wasn't working. The clutch booster must also be able to bleed off boost pressure on its own...which is why you hear the boost leak sound so close to the firewall and on the drivers' side.

Can you guys explain a little more? I'm also having a wooshing boost leak somewhere. Can you show me exactly where you are talking about?

The other thing is, my car HOLDS 13.5 PSI, but it feels like I have a little less power.

[syangvr4]

Originally Posted by etecnifibre

Can you guys explain a little more? I'm also having a wooshing boost leak somewhere. Can you show me exactly where you are talking about?

The other thing is, my car HOLDS 13.5 PSI, but it feels like I have a little less power.

If you look at the back of your plenum there is a larger Vaccum line that goes to your brake booster and to the right of the plenum you have the clutch booster vaccum line. These two hoses I believe contain your check valves. The point of a check valve is to direct air flow one way only. like letting vaccum into the brake/clutch booster and keeping boost out. To indicate if you have bad check valves:

1. You cant brake boost or brake while building boost.
2. Your clutch seems to move at you while building boost.

[phantomrt]

^^^ basically sums it up. There are two large vacuum lines going to the intake manifold. One is for the brake booster, which is on the back (firewall) side and the other is for the clutch booster, which is on the driver's side. The clutch booster hose is about 10"? long and pre-bent. It will install nicely either way but it is supposed to go on only one way. Inside this hose is a check valve (1-way valve)--you cannot tell by looking at the outside of it, but it is in there. Or, perhaps somewhere in the last 15 years someone decided to replace it with a piece of silicone hose or something and the check valve is long gone.

[etecnifibre]

Originally Posted by syangvr4

If you look at the back of your plenum there is a larger Vaccum line that goes to your brake booster and to the right of the plenum you have the clutch booster vaccum line. These two hoses I believe contain your check valves. The point of a check valve is to direct air flow one way only. like letting vaccum into the brake/clutch booster and keeping boost out. To indicate if you have bad check valves:

1. You cant brake boost or brake while building boost.
2. Your clutch seems to move at you while building boost.

Originally Posted by phantomrt

^^^ basically sums it up. There are two large vacuum lines going to the intake manifold. One is for the brake booster, which is on the back (firewall) side and the other is for the clutch booster, which is on the driver's side. The clutch booster hose is about 10"? long and pre-bent. It will install nicely either way but it is supposed to go on only one way. Inside this hose is a check valve (1-way valve)--you cannot tell by looking at the outside of it, but it is in there. Or, perhaps somewhere in the last 15 years someone decided to replace it with a piece of silicone hose or something and the check valve is long gone.

It appears I installed the hose backwards. Thanks for the help, guys.