rx78581

I have a 85 gsl-se that I have done the respeed big brake kit to with new booster and new stock master cylinder all new brake lines and hoses running here is my problem when I am sitting at idle I have great brake pedal but when I get out on the course it goes to the floor please help what am I missing

elwood

iTrader: (1)

Did you retain the check valve in the vacuum hose that leads from the booster to the intake man?

rx78581

Correct me if I am wrong but if I was loosing vacuum wouldn't the pedal get rock hard

t_g_farrell

iTrader: (1)

Answer his question. Do you have the check valve in the hose pointed the right way attached
to the booster?

What you describe is exactly what happens when the booster has no vacuum.

Also you may have air in the lines which means it will go to the floor and feel mushy as well.

rx78581

I just got home and pulled the lines off booster and intake they are the same ones that were on the car before but there is no check valve in the rubber hoses so with that being said were can I get one

rx78581

Well I just replaced the vacuum hose that goes to the booster with check valve in it and still the same issue if anyone has any ideas please let me know

dougingraham

I have not seen a lack of vacuum ever causing the pedal to sink to the floor. I drove my GSL without vacuum for over 2 years and all the lack of vacuum does is make your right leg muscles stronger.

If the pedal sinks to the floor there is either a leak somewhere or the master cylinder is allowing fluid to pass around it instead of applying pressure to the fluid. If the fluid is old or has water in it you can get steam in the lines when the brakes get hot which is compressible. You say you replaced the lines. I assume you replaced the rubber flex lines with the braided stainless. An old rubber hose could be in the process of failing and expanding like a balloon under pressure.

Look for leaks. Bleed the brakes again. Replace the fluid with fresh DOT 4. Don't mix with DOT 5. If all that fails consider replacing the master cylinder again. Take to a competent brake guy if you are unsure of anything.

MazdaMike02

iTrader: (4)

Sounds like air in the system. Bleed the master itself first; have an assistant pump the brakes, then hold it and crack the lines at the master. Do them all at the same time. Then move to the wheels, bleed them in this order; RR, LR, RF, LF.
If you havent replaced all the brake fluid I recommend doing so. If your tracking the car I would get a brake fluid for such purposes, such as DOT 4.1 or 5. Only DOT 3 and 4 can be mixed.