Brake light on on pedal press then off?

[Spool'n Fool]

My brake light started coming on for a moment, when I pressed the brake pedal. Like a good dooby, I put more fluid in the res.. Then the cap didn't seal right, so the fluid went all over. The I resealed and bled the brakes and after 5 pumps with the car off, the res would overflow on the pass res side and spew again.

I then tried bleeding with the engine running, (only fronts)... no big changes..

When running the engine, the res fluid stabilized (lowered toward 1/2 way mark)...

Soooo, what the heck is going on and how does one bleed this set up differently than the typical GM's? Oh yeah, the light is doing the same thing...On for a longer moment now when hitting the pedal with car running. I need to rebleed...

Help!! I need to drive it..

 

[Spool'n Fool]

Accumulator?

OK, I've been educated a little more:

I thought I had a problem because when I stepped on the brake pedal hard, the brake light came on for a split second. I just found out that it is considered normal..

Before I knw that, I had added fluid and it overflowed when trying to conventionally bleed the brakes. I just learned about an accumulator and motor drive.

I've now bled the brakes with the key switch on and they feel only a little better but usable, but the light stays on every time I hit the pedal for a second or two.

Per some info, I did pump the pedal 10X with key off to depressurize the accumulator. It took 6 secnds for the light to go off after turning the key on... I also cleared the accumulator 15X and it took 8 seconds till the brake light went out once the key was turned and motor drive came on.

The last caliper I bled was the driver side front. I read something about a valve and air??

Any hints of cause and cure??

 

[Spool'n Fool]

Brass Proportioning Valve?

I've read that Canada had a recall on the Cast Iron Proportioning valves. Did the U.S? I still have a Cast iron one... I read these are susceptible to air leaks?

 

[zeus87gn]

Yep, you over filled your passenger side bowl. When you depressurize the accumulator (10 pedal pumps with the key off) it empties the accumulator ball. If the bowl is full when you do this, it will spew every time. Normal operation of the PowerMaster, the passenger side bowl should be half full. The other half of the bowl is in the accumulator ball. The drivers side can be full.

Your brake light comes on for 2 reasons...and 2 reasons only. 1 - there is low pressure in the accumulator, 2 - your parking brake is on. I would not call the light action normal unless you have your parking brake on. Your time from motor start to light off is Ok, as long as the motor doesn't run but a few seconds longer before stopping.

Guessing that you are bleeding at the wheels by pumping the brake pedal, you should do that with the key off after you depressurize. If the key is on, you can overwork the motor and can take a chance of burning it up. The pedal will be quite firm while doing this, but it can be done. You can also spew fluid everywhere. There are some that do it with the key on, but it is not my preference. I use a vacuum pump.

If you are still experiencing the brake light when you hit the pedal, it sounds like you may have an accumulator ball going south. If you are doing the pressure bleed in the correct fashion, your brakes are most likely weak from low pressure in the accumulator. The are the first thing to go on these PowerMasters.

If it helps, here is what is going on: the motor pumps up the accumulator, the switch tells the motor when to turn on and off. When you hit the brake, the pressure (& fluid) goes from the accumulator into the brakes and the pressure in the accumulator drops. It is dropping below a certain point when the light comes on, the motor pumps it up enough, the light goes out. But the light goes out at a lower pressure than what the ball can handle. You're acc ball just can't handle what it used to.

You need to run the diagnostic procedure on GNTType to be sure what your problem is. I'll still bet on the ball.

HTH

 

[zeus87gn]

I've read that Canada had a recall on the Cast Iron Proportioning valves. Did the U.S? I still have a Cast iron one... I read these are susceptible to air leaks?

Yep, you need to replace it.

 

[Spool'n Fool]

Is this Prop Valve covered by Buick in the U.S.? If not, where is the best place to get one? I can install..

Also, could this be the issue and the accumulator may be OK? It has the yellow label on it (already replaced once upon a time).. where is the best place to get an accumulator?

I greatly appreciate the input!!!!!!... What a freaking learning experience!

Also another dummy question, If there is no fluid in the accumulator, how can I bleed... or is there just no pressure in the accumulator when I depressurize with the 10 pumps, but still plenty of fluid?

 

[zeus87gn]

Yes, the PowerMasters are a definite learning experience!

The valve i'm not sure of, haven't had to mess with mine. The valve doesn't have anything to do with the accumulator. It just slings pressure and fluid to the wheels when you hit the pedal. The valve proportions the pressure someway between the front and rear wheels.

Accumulators go bad sometimes. Especially if you have old fluid in your system. They like fresh fluid. I use DOT 4. Haven't had a problem for about 6 years. Run the diagnostics, it will tell you a bunch. Ours went through a few of them before I figured out what I was doing. And I am still learning.

Yes, there is some residual fluid in the accumulator but no pressure. If you have to replace it, you will end up cycling the high pressure side of the system a couple of times to get as much of the air out as possible. AKA, pump up then depressurize and wait for the tiny bubbles to go away.

When you bleed, the internals of the cylinder full with fluid only transmit your foot pressure and it should work. I did it once before I got my vacuum pump. It was diffucult, but it worked.

I'll be back online tomorrow...

 

[Spool'n Fool]

Thanks!!!!!!

Since the Accumulators are discontinued from GM, I need to search for one..

Now that I think about it, my 84 had a much nicer and harder pedal.. This one always seemed lower..

 

[zeus87gn]

Kirbans has the Accumulators. I'm going to get one soon for backup. They are a new manufacture, but it's better than nothing.

Run the diagnostics before you spend the money. Be sure. It's a relatively simple procedure. Get a good stopwatch.

 

[DavzGN]

I had the same flash of the brake light when hitting the brakes hard about 7 years ago. I ordered an accumulator for it and while waiting for the accumulator to come I replaced all of the fluid with Valvoline synthetic DOT 3 fluid. I bleed out the brakes until the color of the fluid changed to the lighter color of the new fluid. The new fluid fixed my occasional brake light and I still have the new Accumulator on the shelf (not for sale). I won't guarantee that this will fix yours but for the price difference between brake fluid and an accumulator it's worth a try.

I still have the new brass proportioning valve still on the shelf from that time too.


HTH
David
87GN

 

[zeus87gn]

Agreed.
A fresh flushing of fluid does wonders for the powermaster.
And keep good clean fluid in it.

 

[Blazer406]

Been there done that.....

IMHO it is likely the accumulator.... I picked up a barely used one here on the boards for about $70... worked great... no more light....