Powermaster brakes diagnostic information

[Turbo85]

OK thanks....

 

[Tori]

I need to diagnose my PM system. I've read this entire thread, and the instructions on the first post. My symptom is: hard pedal. I am not sure if my pump works, when i turn on the key, i hear the fuel pump, key buzzer, and there is a light noise under the hood, but it's faint and doesn't last long enough for me to pin point it.
How loud, and how long does the pump run for ? I checked the fuses the other day, and found them all good.

Also, can someone explain how this system works. I need to understand the flow of things so to speak, it'll help me sort the problem. At least to understand things anyway.
BTW, i do have the grey pressure switch.

Thanks in advance

 

[Mike Radice]

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[Coelacanth]

I'm dealing with some brake issues too. The light came on when the ignition was on. Last summer we bled the brakes but before going through this thread and the helpful pictures showing proper fluid levels, we'd overfilled the reservoir after bleeding. I sucked out the excess fluid with a turkey baster and got the level where it ought to be. There is no leaking. Did the 10 pedal presses and now the light doesn't come on with ignition. However, when driving, the light will blip on briefly when the pedal is pressed a good amount. If I'm not mistaken, from reading the diagnostic information on page 1, it's probably a faulty accumulator ball.

1) The diagnostic information that was copy/pasted on page 1 seems to have a good bunch of text cut out. It's hard to read because sentences are cut off. Is it possible to re-copy the FULL text from the service manual?

2) Is my assumption that my accumulator is dying correct? Is it a pretty basic R & R or is there anything important to know before removing/replacing the accumulator ball? EDIT: I found info on how to safely R & R the accumulator here, which requires depressurizing it first:

http://www.gnttype.org/techarea/brakes/accumulator.html

Thanks all!

 

[nevertoold]

I developed a problem with my PM brakes this year. When I turn the key on the brake light stay's on for about 10 to 20 seconds, then goes out. Brakes work fine and never comes on will driving. Only comes on after it sit for a while, like a few hours or overnight.
Checked the service manual.
Symptom: Pump cycle time at pressure switch exceeds 10 seconds
1: Check for air in system-recycle 5-10 pump cycles to remove air. Did this and it fixed the light coming on when the key is first turned on. Great cheep fix.
I noticed that when I charged and depressurized the PM the brake fluid in the reservoir never changed it was always full. I took the cap off just to be sure it wasn't over filled
Back to the service manual
Symptom: Fluid level in pump reservoir does not cycle between full and near empty when accumulator is fully charged and fully depressurized.
1: Check for air in fluid-cycle 5-10 pump cycles to remove air. Tried it again just for the hell of it no change but brakes still work good
2: Check accumulator precharged pressure- replace if low.
I do not have a pressure gauge that will read that high 635-735 psi.
Do I have an accumulator problem or do I have an imagination problem.
Thanks for any help or advice you can offer.

 

[TurboBuRick]

Are you sure you're looking at the right side of reservoir? The passenger side of the tank is used for charging the accumulator.

 

[Coelacanth]

I developed a problem with my PM brakes this year. When I turn the key on the brake light stay's on for about 10 to 20 seconds, then goes out. Brakes work fine and never comes on will driving. Only comes on after it sit for a while, like a few hours or overnight.

Mine was doing that last year when the reservoirs were overfilled. Not sure if that's your problem, hopefully it's that simple.

 

[nevertoold]

Are you sure you're looking at the right side of reservoir? The passenger side of the tank is used for charging the accumulator.

Your right! The passenger side the fluid is lower.
Another cheap fix.
Thanks a lot guy's

 

[BeSerious]

1) The diagnostic information that was copy/pasted on page 1 seems to have a good bunch of text cut out. It's hard to read because sentences are cut off. Is it possible to re-copy the FULL text from the service manual?

I am having a "hard pedal" issue, and trying to diagnose it with those instructions is giving me a migraine.

The brake light came on one morning, along with a very difficult to press pedal.
After driving it home with the hard braking, there was some fluid leaking from the passenger side of the reservoir.

On the advice of others, I checked the fuse. Sure enough, it was blown. I replaced it, and when I turned the ignition to "on"
I could hear the pump running for longer than normal. It strained a little at the end, but it eventually stopped. Can I presume
this means it charged the accumulator?

The brakes worked fine for about a week. Then the light came back on and the fuse had blown again.

Would my first best course of action be to change the pressure switch or the accumulator?

I had seen somewhere else that the fan relay(?) is on this same fuse and could be causing the problem?

Any advice would be appreciated.

Justin.

 

[TurboBuRick]

More than likely the power master motor is overdrawing causing the fuse to blow.

 

[BeSerious]

More than likely the power master motor is overdrawing causing the fuse to blow.

So my options are pretty limited then. Just buy a rebuilt powermaster unit, or switch to vacuum?
I don't think I've even seen just the motor for sale.

 

[Coelacanth]

I am having a "hard pedal" issue, and trying to diagnose it with those instructions is giving me a migraine.

I agree...somebody needs to edit that first post because it's practically gibberish with all the missing text sections.

You might find this flowchart helpful:

http://www.gnttype.org/techarea/images/diagchart.gif

More hard pedal diagnostics here:

http://www.gnttype.org/techarea/brakes/PwrMstr.html

I'd suggest you do the troubleshooting to see if it's the accumulator. If that's the culprit, replacing it is quite easy. You can buy a repro from Kirban for about $200. Replacing it is as simple as depressurizing the existing accumulator with 10 brake pedal presses with the ignition off, remove it, then install the new one and gravity-bleed the brakes. But find out first if you can pinpoint the accumulator as the culprit.

 

[BeSerious]

That flowchart looks very helpful. I am going to go try it now. Thanks.

 

[BeSerious]

Here's a video of what just happened.

Sorry it's sideways.

It doesn't sound good.
That's the radiator fan turning on when the motor/pump starts struggling.

It had never squealed like that until this time.

 

[Coelacanth]

I wish I could be more helpful but you can rule out the accumulator, that's definitely not the source of those noises!

 

[TurboBuRick]

It's hard to hear what's going on once the fan starts..

 

[TurboDave]

Here's a video of what just happened.

Sorry it's sideways.

It doesn't sound good.
That's the radiator fan turning on when the motor/pump starts struggling.

It had never squealed like that until this time.

That's a bad pressure switch, oh, and your engine side reservoir is a bit too full.


Sent from my iPhone 6+ using Tapatalk.

 

[TurboDave]

You also have the somewhat unreliable yellow stripe accumulator! I would replace both. The newest accumulators are VERY reliable! No failures yet.


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[BeSerious]

That's a bad pressure switch, oh, and your engine side reservoir is a bit too full.


Sent from my iPhone 6+ using Tapatalk.

Well that's good news! I will replace both of them, and take some fluid out of the engine side reservoir.

 

[TurboBuRick]

Do a complete fluid change. Press the brake 10-15 times with key off to return all the fluid to the resvior. But remove some fluid from that motor side first. Or you will have a mess to clean up.