Yet another Power Master question/problem

[Wright 63]

Ok, heres my situation. Ive got an 87 GN with 57k. Its been sittin since 2002 when it was wrecked. I had to replace the brake and fuel line on drivers side frame rail after I bought the car in January this year. I also went ahead and did the aluminum drums, 7/8 wheel cylinders, new shoes, new pads and turned rotors on front. It "appears" to have a new power master motor allready on the car. When the switch is turned on, the motor will pump up the system for maybe 3 seconds and stop. When you press the pedal it will go straight to the floor and the motor will run the entire time untill you let off of the pedal. I have tried the bleeding procedure on this site writtin up by Zuess and also the info provided on GN/TType.org with no luck. Anyone have any suggestions other than switching over to vaccume or hydroboost? I have enough p/m brake systems lying around the shop there should be enough odds and ends parts to fix it but have no idea where to start. I tried the acc ball and press switch allready.

Thanks in advance guys.

Brian

 

[Wright 63]

Forgot to mention that the brake light isn't on and that I have the old cast iron proportion valve if this helps.

Thanks,

Brian

 

[zeus87gn]

The car was sitting for 6 years with a broken brake line and you have recently replaced it, correct? Did you bench bleed the master cylinder after you replaced that line? If you didn't, the cylinder is full of air and you need to bench bleed. If you did bench bleed, and got out as much air as you could find, there is only 1 thing that will allow the pedal to go straight to the floor - blown seals in the master cylinder. This is considering that you have also bled at the wheels, and both the slaves/calipers are in good condition and not leaking.

Do you know why it was wrecked? (history behind the crash?)
I'll bet the brakes went out on the driver.

That's ZEUS, thank you.

 

[Wright 63]

Thanks for the reply and sorry about the spelling Zeus. I was wondering if the master cylinder seals were bad. I bench bled twice and got air both times. 2nd time nowhere near as much, mostly the microbubbles. Was gonna let it settle and try again. I bought a vac. bleeder to try and bleed the wheels again and see what happens.

Not for sure what caused the wreck. I bought it from a Dad who got his 16yr old son entirely way too much car for his first one, musta got him rattle snakes for x-mas. He almost made it a week. They took it to the body shop for repair.... untill Momma found out and said HELL NO your not puttin my baby back in that car lol. Thats where it sat untill I wondered across it.

Thanks again for the reply!!

Brian

 

[zeus87gn]

You have to bench bleed until there is no air.
For bench bleeding, microbubbles aren't acceptable.
Try agiain and see what happens.

Something else, I think your acc may be on it's way out.
3 seconds is pretty short. Good time is 7 to 10 seconds.
Do you see the fluid level on the inboard side of the bowl drop down while the pump is running? If so, how far does it go down?

 

[Wright 63]

Well Ive Tried Everything And Decided To The Swap. Havent Decided Which Way To Go Though. Whats Your Opinion On hyd Boost Vs Vac.

 

[zeus87gn]

No contest IMO - Hydroboost.

It's what GM should have kept on the later GN's.

 

[Wright 63]

Ok Thanks For All The Help. I Really Appreciate It. Any Advice Before I Start The Swap?

 

[zeus87gn]

Research the brakes page. There are many threads on this very subject. I don't know all the technical aspects of this conversion....yet. But i do know that it is the better swap than vacuum for a turbo engine.