bmoha2
15+ Year Contributor
- 1,046
- 1
- Mar 3, 2007
-
madison,
Wisconsin
My car has been stuttering under boost for a while. My car's brakes have also been pumping up. The brakes pump up to the point that all freeplay at the brake pedal dissappears and I can feel the brake pads start to drag on the rotors. I eliminated the EGr system on the car with an EGR blockoff plate. All the EGR system including the evap canister was removed and I rerouted the vacuum lines according the the VFAQ diagram. I capped off all of the now unused vacuum ports on the intake manifold that would have been used for various sensors etc. All of the various vacuum connections have been checked and rechecked and they are all sound and have not been leaking. The vacuum system is very simple now. I have one vacuum port that goes off to the Aeromotive fuel pressure regulator and my Blitz dual solenoid digital boost controller. I have one vacuum source going off to the turbo to the Blitz solenoid to the Blitz supersound BOV and then back to the intake manifold. The PCV vents to a catch can. The only other vacuum source port goes from the intake manifodl to the brake booster. I replaced this hose with a new one from the dealer with a new one way vacuum valve. The one way valve is installed from the factory in the hose and the hose is marked with a yellow arrow labeled engine and that side goes to the intake manifold. That part I figure is pretty much as no brainer. The car stuttered under boost and the brakes pumped up before the intake manifold to brake booster/one way valve was replaced and still does it now with a new one. I know the hose isn't installed backwards. If it were the brake pedal would be very hard and very hard to depress with the foot.
My theory is that as I develop boost after it gets to a certain psi the one way check valve to brake booster is getting blown open and/ or over ridden and the brake booster becomes pressurized causing the brakes to pump up. My certified mechanic friend assured me that this is not possible and that there is no way that that is possibly happening. he background is in NA stock fleet vehicles and he doesn't seem to understand the workings of a turbocharged motor. When I said that a intake manifold would be positively pressureized when the turbo spools up he couldn't understand how that would possibly work and not blow the engine apart. He's a nice guy and has helped me out alot in the past but I think this is a little beyond him as he has great difficulty thinking out side the box.
The brake booster needs 18 inches of vacuum to operate properly. As the car idles or is driven around town without boosting on it the brakes do not pump up. As soon as I spool up the turbo past 6 or 7 psi the brakes pump up and I can feel the brake pads start to drag on the rotors.
I have brand new Brmebo slotted rotors in the front and Powerstop crossdrilled cadnium coated rotors in the rear with EBC green kevlar brake pads on all four corners. I also have SS braided brake lines on all four corners and am running Dot4 brake fluid. All of the DOT3 was drained from the system and the brake master cylinder was bench bled with Dot4 prior to filling and bleeding all four corners of the brake system. The brake system has been repeatedly bled with the assistance of a friend. I am confident that there is no trapped air in any of the brake lines. I have taken off each brake caliper individually and ensured that each caliper is not siezed. I also replaced all of the slider bolts on all four calipers to make sure there is no stiction from dirt debris or possibly warped slider bolts.
I recently installed a FP BigT28 turbo with a new three layer exhaust manifold gasket, DNP SS tubular exhaust manifold, new ss turbo to exhaust manifold gasket, SS exhaust manifold studs, washers and nuts, and new turbo to O2 sensor housing gasket. I also replaced the front oxygen sensor and installed a 190 lph Walbro fuel pump. I have checked and rechecked all the connections and have not found any leaks at any of the junctions. The car is running without any CELs.
I took the car out for a spin the other day. Warmed it up and after it was warmed up boosted on it just to 7 or 8 psi. There was no sign of the brakes pumping up before I started boosting on it. As soon as I boosted on it, within 30 seconds, the brake pedal pumped up, the brake pedal freeplay dissappeared and I felt the brake pads start to drag on the rotors. i drove it staright home and dissconnected the hose that goes between the brake booster and the intake manifold and it was pressurized. It is definitvely a big issue as when it first started to happen I was slow to figur eout what was happening and by the tme I did the brake pads were draggin on the rotors to the point that the right front brake caliper caught fire. That is to say, the high temp red paint I painted the right front brake caliper with caught fire. I can't drive the car at this point because of this problem. The hose with it's built in one way valve was brand new just weeks ago when I installed it. I am feeling pretty frustrated because like I stated before my certified mechanic friend told me this couldn't possibly be happening. plus I have never heard of this happening on any other DSMs, no posts on forums, nada. I hate to go buy a new hose and one way vacuum check valve just to have the exact same problem still happen. I am tempted to block off the port that goes to the booster on the intake manifold and install an electric vacuum pump that would be capable of providing the 18 inches of vacuum the brake booster needs but that seems kinda like a hack idea.
My theory is that as I develop boost after it gets to a certain psi the one way check valve to brake booster is getting blown open and/ or over ridden and the brake booster becomes pressurized causing the brakes to pump up. My certified mechanic friend assured me that this is not possible and that there is no way that that is possibly happening. he background is in NA stock fleet vehicles and he doesn't seem to understand the workings of a turbocharged motor. When I said that a intake manifold would be positively pressureized when the turbo spools up he couldn't understand how that would possibly work and not blow the engine apart. He's a nice guy and has helped me out alot in the past but I think this is a little beyond him as he has great difficulty thinking out side the box.
The brake booster needs 18 inches of vacuum to operate properly. As the car idles or is driven around town without boosting on it the brakes do not pump up. As soon as I spool up the turbo past 6 or 7 psi the brakes pump up and I can feel the brake pads start to drag on the rotors.
I have brand new Brmebo slotted rotors in the front and Powerstop crossdrilled cadnium coated rotors in the rear with EBC green kevlar brake pads on all four corners. I also have SS braided brake lines on all four corners and am running Dot4 brake fluid. All of the DOT3 was drained from the system and the brake master cylinder was bench bled with Dot4 prior to filling and bleeding all four corners of the brake system. The brake system has been repeatedly bled with the assistance of a friend. I am confident that there is no trapped air in any of the brake lines. I have taken off each brake caliper individually and ensured that each caliper is not siezed. I also replaced all of the slider bolts on all four calipers to make sure there is no stiction from dirt debris or possibly warped slider bolts.
I recently installed a FP BigT28 turbo with a new three layer exhaust manifold gasket, DNP SS tubular exhaust manifold, new ss turbo to exhaust manifold gasket, SS exhaust manifold studs, washers and nuts, and new turbo to O2 sensor housing gasket. I also replaced the front oxygen sensor and installed a 190 lph Walbro fuel pump. I have checked and rechecked all the connections and have not found any leaks at any of the junctions. The car is running without any CELs.
I took the car out for a spin the other day. Warmed it up and after it was warmed up boosted on it just to 7 or 8 psi. There was no sign of the brakes pumping up before I started boosting on it. As soon as I boosted on it, within 30 seconds, the brake pedal pumped up, the brake pedal freeplay dissappeared and I felt the brake pads start to drag on the rotors. i drove it staright home and dissconnected the hose that goes between the brake booster and the intake manifold and it was pressurized. It is definitvely a big issue as when it first started to happen I was slow to figur eout what was happening and by the tme I did the brake pads were draggin on the rotors to the point that the right front brake caliper caught fire. That is to say, the high temp red paint I painted the right front brake caliper with caught fire. I can't drive the car at this point because of this problem. The hose with it's built in one way valve was brand new just weeks ago when I installed it. I am feeling pretty frustrated because like I stated before my certified mechanic friend told me this couldn't possibly be happening. plus I have never heard of this happening on any other DSMs, no posts on forums, nada. I hate to go buy a new hose and one way vacuum check valve just to have the exact same problem still happen. I am tempted to block off the port that goes to the booster on the intake manifold and install an electric vacuum pump that would be capable of providing the 18 inches of vacuum the brake booster needs but that seems kinda like a hack idea.
