1987 buick turbo brakes acting up

[bigG]

my 1987 buick turbo brakes have about a one second delay and the dash light comes on before I have any brakes thanks, Brad

 

[turbojd]

Could be the electric motor going on the powermaster, or the accumulator.

 

[POWERBRAKEBOB]

Hydroboost Conversion

Those Electric Motor/pumps Wear Out The Vanes, Or The Seal Leaks Brake Fluid Into The Windings, And Shorts It Out. Read On About The Hydroboost Conversions.

 

[Lynn D. Brown]

I guess there a few guys who have learned how to rebuild the troublesome PM. A few more of us have switched to vacuum, and if U do, U probably won't have to do anything after this. My vacuum has had no problems for 100 K+ miles. However, I also don't have alot of holding power at the line.

I have tried the max soft rear lining and bigger rear cylinders, but still don't hold for sh*t. Not sure what to do next. I'm wondering if anyone has an adjustable proportioning valve to replace the stock front valve ? Haven't seen one yet. I put in a rear adjustable valve at somebody elses' suggestion long before I knew anything, and now I'm thinking that that was stupid, so maybe I should pull that out. I mean why would U want to cut the pressure to the rear when U don't have enuf pressure there to hold ?

Maybe I could go w the Hydraboost, but that's alot of $$, and looks like alot of work. Could consider big rear discs, but that ain't too cheap either, and then how would U balance front & back ? I guess I'll do something eventually, but I just don't see a clear path.

 

[zeus87gn]

G-

You need to run diagnostics. Look here -> Brake System

Most likely it is your accumulator, but you need to rule out your pressure switch and pump. Get a good timepiece and goto it. Post up with your results if you don't understand them. Pay close attention to the time it takes ot pressurize the system and the time (if any) to self cycle.

Any questions?

 

[wagon]

Old brake fluid can cause some problems too. One of mine was acting up, and I just emptied out the reservoir, and replaced it with clean fluid.(Pump the brake pedal a few times first, so that you get as much as possible.) Try bleeding the brakes too, to get all of it. My fluid was pretty old and grungy looking. The light used to come on every once in a while when I put on the brakes, and when first turning on the car, it would take a long time for the light to go out and the pump to stop. Not any more. Cheapest first thing to check. If that doesn't help, then I would guess accumulator or pump(not like there is much left).

 

[POWERBRAKEBOB]

Hydroboost Conversion

The factory prop valve is designed to cut the rear brake pressure in half. Most drum brakes lock up at 600psi. The problem with that, is, discs need 1200psi or more. to set the car down. The prop valve holds down the drum brake pressure to allow the front pressure to rise. Havng a stock valve, which cuts the pressure in half, and then a second adjustable valve cuts the rear pressure down even more, which overheats the fronts. To run an adj valve, the stock prop valve needs to be changed to a 4 disc type, and add the adj valve after it. Changing to rear discs only compounds the brake problem. Going from a 3/4" wheel cyl to a 2.5" caliper requires double the volume from the master to fill it, and because disc brakes do not "self energize" like drums do, then the pressure has to be raised up to 1200psi, like the fronts. All factory 4 disc cars have high volume, high pressure, boosters to make the system work. If you look at most new cars, the vacuum boosters are huge. On new cars, even without turbos, they have a tough time getting vacuum out of a F.I. motor. Mr. Dreamcar says his car can hold 22lbs of boost with the foot on the brake, and all the brake problems go away. In the powermaster, the piston seals rarely go bad. It is, 90% of the time, a worn out motor/pump. I have new ones, but the replacement of parts with the powermaster goes on forever.