powermaster problems maybe?

[87ttypeV8]

just purchased a 1984 grand national with the powermaster brake unit... it was converted at some time....

ok here is the list of problems and wondering what is wrong
everytime i step on the brake.. the brake light on the dash comes on... i think just bad wiring since the car is a wiring mess

when i step on the brake it is really soft until i press down pretty hard? is this normal.. my other car is a 1987 t type with vacuum brakes and there are pretty firm... are powermasters just soft?

when at a stop and i press on the brakes... the pedal will stop about 3/4 the way down and seem like that is as far as it goes... then if i push down a lil harder the pedal goes all the way down to the floor

there are no leaks on the unit and i am new to the powermaster set up... please help me out!!

 

[TurboBuickSix]

It will act lke this if the level of fluid in not perfect according to spec.It was critical that it be in between the marks on the inside of the resevoir after pumping brakes 10 times with key off.If that checks out follow the diagnostic tree on gnttype.org.

 

[toddmingnworld]

I'm not sure but does your 84 GN have the accumulator
bowl, my 87 was doing the exact same thing & my vendor replaced the bowl & the problem vanished. It cost $170.00
for the bowl...Just my .002

Todd

 

[BJM]

Assuming it is in fact a PowerMaster and not the Hydro Boost system, it sounds like your accumulator.

Check my response in this thread Accumulator check

It will determine what major component is messed up.

 

[87ttypeV8]

ok given my accumulator ball thingy is bad... which is probably is for sure.... can i drive the car around at all like little trips around maybe or will this cause brakes to fail?
seems like they work fine but i dunno.. please help me out on this on since i dont want to crash and die

 

[BJM]

The power assist drops off a cliff at the accumulator's precharge pressure. Try stopping by pumping until the pedal goes hard, the pump will be trying to catch up the whole while. See if you can manage to stop. A small woman would have a really tough time. I unplugged the PM motor at the unit and went around the block for fun. Its a tough push on the pedal, not a huge deal but if you are not prepared for it, it might seem like there are no brakes at all.

 

[toddmingnworld]

BJM,

Agree 110%, exactly what you described happened to me....

87ttypeV8,

If you do not plan on replacing it anytime soon, keep plenty of distance between you and the next guy because the pedal can be really really soft....

 

[BJM]

According to the manual, pumping repeatedly will eventually get ahead of the pump and drain off boost pressure until the light comes on. This is normal behaviour. You have to pump more than you would in any normal braking situation however. But as the accumulator drains off, the onset of this problem creeps into the normal range of brake usage.