I Fixed It When It Wasn't Broken, Now It Is.

[dougie]

A few weeks ago I decided to replace the brake fluid on my 86 GN. Although the brakes worked fine, the fluid looked brown, I know it was old and the brake pedal was soft. For all I know it might be original. I still have the Power Master, and I bled them like regular brakes. I pushed about 2 quarts of fluid through to be sure I replaced it all.

I drove the car around the block a few times and brakes seemed fine. Then I noticed brake fluid on the garage floor. I checked the level in the reservoir and the level had risen to the very top and had overflowed. I remove some fluid, pumped the pedal a few times with the engine off and the pedal firmed up. I didn't drive the car, but checked back a few days later and pumped the pedal again with the engine off. I heard a hissing noise, and found the reservoir overfilled again, and fluid was dripping off the side of the M/C as I pumped the pedal. I opened the resrvoir and the half toward the passenger side looked like a milk shake. I removed some more, and let it sit. After it looked normal, I repeated pumping the pedal and it turned to milkshake again, again only on the passenger side of the reservoir. I did it a few more times, and it stopped overflowing, and looked OK.

Then I started the car to try the brakes. When I started it, the brake light was on, and I could hear a buzzing coming from the PM. As my son pressed the brake pedal, I could feel and hear it in the unit.

Does anyone have any idea what happened? Any and all suggestions will be greatly appreciated. Thanks.

 

[SRGN]

You're supposed to cycle the pedal 25 times before checking/adjusting fluid level. The brake light will normally be on for a brief period when the key is turned on after this, as the unit has to build pressure to replace the pressure that was bled off during the pumping of the pedal with the key off. The level in the reservoir will drop as well. Sounds like it was just overfilled.

 

[carlsbadGN]

Assuming the brake light went off, you're probably OK. If the light stays on, the accumulator may be giving up the ghost.

The milky appearance of the brake fluid is caused by air bubbles. To purge the air bubbles, you need to pump down the accumulator a few times until the evacuated fluid looks clear. Do this by pumping the brake pedal about 15 times with the key off, then remove the MC cover and look for air bubbles in the fluid (on the passenger side). If there are a bunch of bubbles, let it set for a few minutes to dissipate, then turn the ignition on (don't start engine) and let the accumulator re-pressurize. If the fluid is dirty and milky when you depressurize the accumulator, remove the fluid with a turkey baster or vacuum bottle and replace with fresh brake fluid. You may need to de-pressurize the accumulator multiple times before the fluid looks clear of air bubbles.

Fill the passenger side of the MC with fluid only after the accumulator has been pumped down, as the level will rise as fluid is evacuated from the accumulator. About 3/4 to 7/8 of an inch below the bottom of the MC cover should be about right. Also, don't forget to replace the MC cover each time before pumping down the accumulator, or you'll have a brake fluid mess.

 

[dougie]

Thanks,

I'm going to give that a try. The Brake light stayed on, but I only ran it for about a few minutes. Hopefully it's nothing serious.

 

[carlsbadGN]

I forgot to mention that Zeus87gn has posted a lot of insightful information on the PM system. Look up his posts for further help.

 

[JimP]

Not to be a kill joy, but I was chasing a few power master problems which I could never re-create. On a couple of occasions I was without brakes all together. If all else fails, convert to vacuum. Best mod I had ever done to this car hands down. For a new master cylinder, and a rebuilt dual diaphragm booster and about 2 hours of my time, for less than $300.00 Canadian I went to vacuum.

The brakes feel amazing, either way I hope you get your issues figured out, but if you were on the fence and a repair is more than a couple of hundred bucks, vacuum is a great way to go. Other mods in Sig.

 

[dougie]

OK, I followed the procedures for getting the air out of the accumulator, and it seemed to be working fine. After several cycles of pumping it up and bleeding it down, the fluid was clear with no air. So I started the car, and the Brake light went out on the dash. So far so good. I hear the PM running, then it got much louder, so I turned the car off. Opened the fluid reservoir and the P/S bowl was sucked dry. I never stepped on the brake pedal. Isn't the PM motor supposed to turn off? More importantly, where did the brake fluid go? Once during the process, the reservoir went low I added fluid, then it overflowed when I pumped the brake pedal. Now I'm more confused than ever because I don't know if I have too little or too much fluid in the system. Is fluid stored in the accumulator ball? Remember, everything worked perfectly until I bled the brakes lines. At that time, all I did was bleed the brakes using a Mity-Vac and never let the bowls get too low working from the farthest to nearest wheel.

Any ideas? Thanks.

 

[dougie]

OK, I followed the procedures for getting the air out of the accumulator, and it seemed to be working fine. After several cycles of pumping it up and bleeding it down, the fluid was clear with no air. So I started the car, and the Brake light went out on the dash. So far so good. I hear the PM running, then it got much louder, so I turned the car off. Opened the fluid reservoir and the P/S bowl was sucked dry. I never stepped on the brake pedal. Isn't the PM motor supposed to turn off? More importantly, where did the brake fluid go? Once during the process, the reservoir went low I added fluid, then it overflowed when I pumped the brake pedal. Now I'm more confused than ever because I don't know if I have too little or too much fluid in the system. Is fluid stored in the accumulator ball? Remember, everything worked perfectly until I bled the brakes lines. At that time, all I did was bleed the brakes using a Mity-Vac and never let the bowls get too low working from the farthest to nearest wheel.

Any ideas? Thanks.

 

[dougie]

You know what, now that I think of it, maybe I did step on the brake pedal while it was running. Don't know if that would matter. Any help would be greatly appreciated.

 

[GNRick]

Yes, the fluid goes into the accumulator. When you step on the brake pedal multiple times with key off, it comes out of the accumulator, thus making it safe to remove the accumulator. This also depressurizes the accumulator.

 

[ChavoLC2]

PM Brakes

Now pump the brake pedal 10x's and depressurize the acc , brake fluid should return to bowl.. Check brake fluid and fill accordingly. That's happened alot of times and usually by a mechanic that knows nothing about these wonderful brakes. They don't depressurize the acc by pumping the pedal and see that fluid level is low and they add some. Now you have a brake system that is over filled both the res. bowl and ball are filled. Buddy of mine used to zip tie the cover so they couldn't take it off and had a sticker telling them to leave well enough alone. Hopefully you will get her back to normal.

 

["Turbo-T"]

That's the sucky thing about the powermaster, is most techs don't know anything about it. They'll fill it to the top not knowing all it's going to end up doing is overflowing out of the reservoir and all over down the fire wall onto the floor/ground, taking some of the paint with it.

 

[carlsbadGN]

dougi:
I couldn't log on yesterday evening for some reason. Ddi you get the PM problem resolved?