1987 GN brake pedal going to floor

[Victor M.S]

I have a issue when i bought the car it was already doing it so i changed master cylinder rear break cylinders and proportioning valve...my pedal keeps going down slowly to the floor only things i got left to change its front calipers and lines plz help me its been a year n cant figure it out

 

[Victor M.S]

The car was converted to vacumm. No more power master by the way

 

[TurboBuRick]

Does the pedal return or get stuck?

 

[Victor M.S]

It returns ...car stops well but when im sitting at the light pedal start going down n got to pump it to keep the car from going forward..thanks for replying by the way

 

[TurboBuRick]

Does the pedal stay up after you pump? If so there is still air in the system.

If the pedal keeps going down even after you pump the pedal, the master is bypassing.

 

[zeus87gn]

Pedal to floor creep is a classic symptom of a dying master cylinder
The only other thing that will do it is a major fluid leak that would be obvious to the naked eye
Depending on where you got the replacement cylinder from it could be the cause

 

[Victor M.S]

I bought it new at napa trying to fix the problem but it still doing the same ..after i pump it pedal stays up for like 30 seconds then strats going down again

 

[zeus87gn]

In that case, check close for leaks
It may even be worth sliding the master cylinder off the booster can and checking for leakage into the booster
If you cant find any leaks at all anywhere, the only other possibility is the master cylinder
vacuum brakes are real simple
I have seen new parts from parts stores be bad right out of the box - it can happen

 

[Victor M.S]

Yeah ur right im gonna go ahead and check that right now ill keep u guys posted thanks for ideas guys

 

[gsgnnut]

Been there done that. Classic master cylinder issue but for giggles check the booster check valve is holding vacuum.

 

[Victor M.S]

So i might have a faulty new master cylinder right? ...n im sorry for this question but how to i check if the check valve is holding vacumm?

 

[zeus87gn]

Youd' have to put a vacuum pump on it and get it up to about 18-19" of vacuum on the high side to see how much it holds

 

[Victor M.S]

Oh alright thanks im gonna try that next i need to fix this a.s.a.p thanks for sharing guys

 

[TLIMITED]

Did you bench bleed the master cyl. before you put it on?

 

[TexasT]

Bleed the master and start at the pass rear, Dr rear, pass front then Dr front last. Put a 2x4 block of wood under the pedal so your helper doesnt over stoke the master cylinder. Keep the master cylinder topped off. If you run it dry youll need to start again from the beginning.
If it still won't hold a pedal you probably have a bad master cylinder.

Sent from my HTC PH39100 using Tapatalk

 

[TurboBuRick]

A simple way to check if the booster is holding vacuum is to start the engine for a few seconds then shut it off. Pull the check valve out of the booster. If the check is good you will hear the vacuum pressure being released.

 

[Victor M.S]

Thank u guys i have been working so havent had time to do anything but hopefully i have time today in the after noon so ill keep u guys posted all ur ideas r trully useful i learn more n more on this forum thank u guys again