Why does my brake light randomly come on?

["Turbo-T"]

Sometimes when hitting the brakes the brake light on the dash will come on.

I know this typically means there's a loss of pressure in the system but the car seems to still stop ok, it just sometimes comes on when braking.

My car still has the power master brake system with I think a replacement accumulator (has the yellow sticker on it) and the switch on top that was notorious for going bad was replaced some time ago with a grey one.

The fluid level is at the half mark and it doesn't seem to be losing any fluid or leaking that I know of.

What's your thoughts on this? Should i convert to vacuum brakes?

 

[zeus87gn]

Try cycling it first. It may just have air in it.
It costs nothing, only take a few minutes, requires no tools, and you can determine it's health in the process.
Procedure is linked in my sig.
Ask questions if you need to.

Sometimes you have to give the acc a wake up call.
It is possible that the acc is going bad. Most typical failure part.
It does happen if left with air in it for long periods.
Be glad your light is working and giving you warnings to check it out.

If the acc is bad you can replace it in a few minutes once you get one. It is a little expensive these days (about the cost of the vacuum conversion) but only takes a few minutes to change. the vacuum conversion will take you several hours and then you have to bleed it.

Z

 

["Turbo-T"]

I'm not really sure what you mean by "cycling it".

Also just a heads up I recently had the brake fluid drained and flushed.

I did notice if I pump my brake pedal 10 times with the key off and then turn it to run the motor runs for about 10 seconds afterwards. 7 seconds is the norm right?

 

[zeus87gn]

What you have done is cycling.
Pump down then pump up.
Check for air in between.

7 seconds is "perfect".
10 seconds is still Ok.....usually.
Is your light still coming on as it was before?
If it is, you need to check for an internal leak.
I'm guessing there are no signs of external leaks?

 

[ITSNOTAGN]

the car is trying to tell you to take that death trap powermaster off before you wind up in a light pole. that is all
Gary

 

["Turbo-T"]

What you have done is cycling.
Pump down then pump up.
Check for air in between.

7 seconds is "perfect".
10 seconds is still Ok.....usually.
Is your light still coming on as it was before?
If it is, you need to check for an internal leak.
I'm guessing there are no signs of external leaks?

The light comes on intermittently. It's really wierd, it's at random, but it doesn't come on that often.

I did see notice a little fluid under the m/c and around where the m/c mounts on the fire wall and the bracket that holds it all up was minorly damp...not soaking wet but there was evidence of a small leak. I sprayed the area with brake parts cleaner and so far I'm not seeing any new leaks, not even after 2-3 days of driving the car.

For all I know the guys that drained and flushed the system may have spilled fluid all over it.

 

[zeus87gn]

For all I know the guys that drained and flushed the system may have spilled fluid all over it.

Oh..........my God. You had a shop do this?
Please tell me is wasn't Midas.
Please tell me they were Buick knowledgable.
I'm will guess that this problem didn't start happening until after you got it back and you didn't have any problems before? I would hate to hear another "They tore up my P/M".

The light comes on intermittently. It's really wierd, it's at random, but it doesn't come on that often.

I did see notice a little fluid under the m/c and around where the m/c mounts on the fire wall and the bracket that holds it all up was minorly damp...not soaking wet but there was evidence of a small leak. I sprayed the area with brake parts cleaner and so far I'm not seeing any new leaks, not even after 2-3 days of driving the car.

Ok, you need to test for internal leaks. I have just described this to another board member over at the bottom of my procedure page. If you don't have any you're lucky. It may only be a bad switch.

You also need to check the switch at your prop valve and make sure it's wires are not grounding out. Also check your parking brake wire. These two items also operate this light. Maybe it's simple.

 

["Turbo-T"]

Oh..........my God. You had a shop do this?
Please tell me is wasn't Midas.
Please tell me they were Buick knowledgable.
I'm will guess that this problem didn't start happening until after you got it back and you didn't have any problems before? I would hate to hear another "They tore up my P/M".

No it was not Midas. It was actually an independent garage that also has a speed shop. I don't know if they're real knowledgeable on turbo Buicks but they are knowledgeable on LS1's, 4.6/5.0 Mustangs and Hondas. Pass by their shop on any given day and you can be sure to find 4.6/5.0 Stangs, LS1 F bodies and an assortment of old school muscle cars set up for the strip.

I want to say this issue was before having the system flushed. All I remember was the fluid was a dark brownish color and I learned on here them powermasters don't like dirty fluid.

Also of interest, I noticed the day I got this car the brakes were nothing like the ones on my other Regal which was a n/a car with vacuum brakes. I liked the vacuum brakes better.

 

[zeus87gn]

No it was not Midas. It was actually an independent garage that also has a speed shop. I don't know if they're real knowledgeable on turbo Buicks but they are knowledgeable on LS1's, 4.6/5.0 Mustangs and Hondas. Pass by their shop on any given day and you can be sure to find 4.6/5.0 Stangs, LS1 F bodies and an assortment of old school muscle cars set up for the strip.

I want to say this issue was before having the system flushed. All I remember was the fluid was a dark brownish color and I learned on here them powermasters don't like dirty fluid.

Also of interest, I noticed the day I got this car the brakes were nothing like the ones on my other Regal which was a n/a car with vacuum brakes. I liked the vacuum brakes better.

Well, at least the Midas morons didn't get ahold of it.
From what you have described so far and the fact that it's still stopping your car, you're not bad off. You may just have an electrical issue or air trapped in your prop valve when they tried to pressure bleed it and blew fluid all over the place.

Test for the internal leaks and post up. If you don't have internal leaks, you problem lies outside the PowerMaster.

 

[XLR8]

I'd bet it's the accumulater ball.

 

["Turbo-T"]

I'm actually beginning to think it's the pressure switch. I noticed some fluid around it where it mates into the master cylinder and also especially where the plastic and metal meet.

I'm just wondering if I remove the switch do I need to bleed the m/c? (I know I gotta relieve it of pressure)

 

[turbojd]

I'm actually beginning to think it's the pressure switch. I noticed some fluid around it where it mates into the master cylinder and also especially where the plastic and metal meet.

I'm just wondering if I remove the switch do I need to bleed the m/c? (I know I gotta relieve it of pressure)

It was years ago, but if I remember correctly when I replaced my powermaster brake switch I just unscrewed it and put a new one in, then a week later brake light again, then I replaced the accumulator, after that I converted to vacuum brakes.

 

[zeus87gn]

I'm actually beginning to think it's the pressure switch. I noticed some fluid around it where it mates into the master cylinder and also especially where the plastic and metal meet.

I'm just wondering if I remove the switch do I need to bleed the m/c? (I know I gotta relieve it of pressure)

I saw you other posts where you switch was leaking. Good find.
The P/M should have 0 leaks.
No. You don't have to bleed the m/c to change the pressure switch.
Yes, you have to pump it down to change it.
Good that you knew that.

The high and low pressure sides of the P/M are separated.
You may want to cycle the high pressure side a time or two to be sure you get the air out from changing the switch. It will only be a tiny bit that is in there, but it will be in there.

 

[TurboDave]

I'm actually beginning to think it's the pressure switch. I noticed some fluid around it where it mates into the master cylinder and also especially where the plastic and metal meet.

I'm just wondering if I remove the switch do I need to bleed the m/c? (I know I gotta relieve it of pressure)

All you have to do to replace the switch is pump the brake pedal a good 10 times or so with key OFF to relieve system pressure. Then slowly unscrew the old one and screw in the new on. Clean everything up and keep an eye on things. Could be a bad switch may be taking out the accumulator.
If the random light keeps up, it's time for a new accumulator.

 

["Turbo-T"]

Thanx, I do have a new accumulator on hand. As for the switch swap, the system is totally relived when the pedal gets hard correct?

 

[zeus87gn]

Yes, that's correct.
About 10 pedal pumps with the key off will relieve the system pressure.
If the acc is on it's way out, sometimes it may only be 8 pumps.
It can vary, but after the pedal gets hard to push it's good to give another pump or two for good measure.
Just to be sure.

 

["Turbo-T"]

Thanx again. I think mine took 15 pumps before it hardened up.

 

[BuickMike231]

This happened with my car too, the brake light would come on every now and then when the brakes were applied. It got more and more frequent and I was told by my buddies (who had all had the same problem in the previous months) to change the accumulator. I changed it and it hasn't come on since and the brakes are fine. It's a very fast job too.

 

["Turbo-T"]

You know I might just go ahead and install the new accumulator while I am at it. I want to say I read something that has to be done to the old accumulator....like bleeding it or something like that......??

BTW I wanted to post these pics....

Old one:

New one:

Hope that's the right one

 

[zeus87gn]

Thanx again. I think mine took 15 pumps before it hardened up.

Ok, this being the case, and your aparent switch leak points directly to the switch. The acc has plenty of reserve. It is most likely Ok.

If you want to, you can change the acc. It won't hurt a thing. As you have a new one, you can test it against your old one and find out just how good of shape it is. But you have to bleed (cycle) the air out of either one when you install it.

If you don't know, your old one is a 2nd generation. Your new one is a 3rd generation. They are equal in reliability/quality/durability so far as I can tell. I have them both and cross tested them against eachother. No difference in pump up time.

P.S. - Don't listen to the haters. The P/M is a good unit.