The PowerMaster Bleeding Procedure

[Lee Thompson]

What do I do now?

I just installed another unit and did not have enough fluid in the pass. side when I turned the pump on. Thanks for all the info.

 

[zeus87gn]

I just installed another unit and did not have enough fluid in the pass. side when I turned the pump on.

What are you asking?
Did you run the pump dry?
Was this a fresh reman or a used unit?

 

[Lee Thompson]

Ok

I doubt that I run the pump dry but @ least the sump was empty. I filled it up and now the pump cycles as it should but the lite comes on every time I hit the brakes. This is a used unit that was working perfectly according to the gentleman I bought it from and I do believe him. The PM is new to me. The car is one I purchased last summer and @ that time there was a leak and the lite came on with each apply. It has the cast iron proportioning valve. Should I change that? Could that cause a problem? Thanks for your time.

 

[zeus87gn]

You should never put used brake components into service....especially when it comes to the P/M.

Ask yourself this question...why sould someone purposely change a properly functioning brake system? There's no (logical) reason for it. There's obviously something wrong with it or else we wouldn't be having this conversation.

What was wrong with your old P/M?
Have you changed any of the components on this replacement P/M?

Try this....
Pump it down for another cycle and when you pump it up leave the key on, let it sit still and don't touch it. Time how long it takes for the motor to come on again (from the moment it shuts off on this pump up). You are checking the self cycle time of the motor. This tests for internal leaks on the high pressure side of the P/M. You want this time to be more than 2 minutes. More than 5 minutes is even better.

By the book, a self cycle time of less than 2 minutes indicates an internal leak and the unit should be rebuilt.

Edit: Your proportioning valve has nothing to do with this. This is a problem in the P/M itself.

 

[Lee Thompson]

Disregard all my post in this thread

It is obvious you know the PM which most people do not. Kinda reminds me of having a conversation with Red Armstrong (or my wife). Thanks you for your help. I will eventually get it fixed. BTW, A lot of people are switching to vacumn or better yet hyd. boost.

 

[zeus87gn]

Trust me, I would never try to take the place of either one of them!
:biggrin:

Red has a d@mn good fuel pump.
It's been running in our tank for years.

Good luck and let me know if you need any more help.

 

[CruznTType]

Hey Zeus
Iam experiencing problems with my 87 T (65,000 miles all orginal). Motor runs everytime I put on the brakes (red light does not come on). Turn it off, pump it down - turn it on 14-15 sec. pump stops. Let it sit 5 minutes no cycle. When I opened top after pump dowm very foamy - cleared in about 3-5 minutes.
What cha think? I need help!

 

[zeus87gn]

Cruzn,

Foamy fluid on pump down is a direct indication of air in the acc.
Cycle it a couple more times to be sure you get all the air out.
Once you get no foamy fluid or any air bubbles on pump down, you have it.
Make sure not to run the bowl dry!

Now, what is the pump up time once you have the air out?
And does the motor run every time you hit the brakes now?

Z

 

[Sweet6]

What happens if you empty the resevoir dry when bleeding the brakes? What problems does it cause and how do you fix it if it can be fixed?

 

[zeus87gn]

If you run the bowl dry, you take the chance of ruining the vanes in the pump.
If it only ran dry for a second, you are probably Ok.
If it ran dry for more than a second, you will have to time it (pump up time) to find out if you messed it up.

If you have ruined it, it has to be replaced.
Contact Hank Terry. He makes them NEW.

 

[dentmasters01]

Cruzn,

Foamy fluid on pump down is a direct indication of air in the acc.
Cycle it a couple more times to be sure you get all the air out.
Once you get no foamy fluid or any air bubbles on pump down, you have it.
Make sure not to run the bowl dry!

Now, what is the pump up time once you have the air out?
And does the motor run every time you hit the brakes now?

Z

In a "good working" system, if its not supposed to run every time you apply the brakes, how many time WILL you be able to apply the brakes BEFORE the motor runs again??

 

[zeus87gn]

In a "good working" system, if its not supposed to run every time you apply the brakes, how many time WILL you be able to apply the brakes BEFORE the motor runs again??

I should check my system to be sure I know a firm answer.
Off the top of my head, maybe 3 or 4 times.
I would think it could vary slightly.
Not every accumulator, pump & switch made will be "exactly" the same.

 

[aminga]

I should check my system to be sure I know a firm answer.
Off the top of my head, maybe 3 or 4 times.
I would think it could vary slightly.
Not every accumulator, pump & switch made will be "exactly" the same.

After a fresh rebuild with a new accumulator mine runs every 2-3 times.

 

[dentmasters01]

I can get one full pump out of mineo and on the start of the second pump, it starts the motor again. I have a brand new acc. on it and after depressurized it runs for 14-15 sec. on start up.

 

[BEATAV8]

Nice write-up Zeus. This should be a sticky.

X2 STICKY!

 

[zeus87gn]

I can get one full pump out of mineo and on the start of the second pump, it starts the motor again. I have a brand new acc. on it and after depressurized it runs for 14-15 sec. on start up.

It sounds like you might have air somewhere in the system.
14 sec on pump up isn't too bad, that's what mine has been running for a while now.
I didn't remember to check my time over the weekend, let me try again tonight.

How long does the pump run when it starts on the second pump?

 

[dentmasters01]

ok, I just tested it out and after pump down, it takes about 14 sec. to pump up, like I stated before. I apply pressure for one full stroke and at the start of the second stoke the motor cycles on for 5 sec. and turns off.

One thing I noticed. I cycled the acc. about 5 times the other night and removed all the air out of it. I drove the car about 2 miles sunday (to test out my new tires on the street) and its been in the drivway eversince. After the above test I decided to pump the acc down again and there is just as much air in it now as the first time I did it a few days ago ?? Its a brand new, out of the ac/delco box acc. any ideas??

edit: I do remember I didn't bench bleed the powermaster when I installed it on my car last year. could there still be air in it that getting in the acc.?? I have, however, blead the lines extreemly well at all corners.

 

[zeus87gn]

Mmmm, this is a tough one.

After the above test I decided to pump the acc down again and there is just as much air in it now as the first time I did it a few days ago ?? Its a brand new, out of the ac/delco box acc. any ideas??

Ok, brand new out of the box GM. Sounds like a second generation acc, right? It would have the nut embossed on the outside and surounded by a yellow printing. Those haven't been made for probably pushing 5 years now (guestimate). It is possible that your "new" acc may have outlived it's shelf life and the diaphragm is leaking nitrogen. I don't know the materials of the diaphragm, but they don't last forever.

edit: I do remember I didn't bench bleed the powermaster when I installed it on my car last year. could there still be air in it that getting in the acc.?? I have, however, blead the lines extreemly well at all corners.

Bleeding at the corners will not get all the air out of the low pressure side of the master cylinder. Bench bleeding is the best method of doing this. Even so, what little air is in there won't make it back into a pressurized acc and even if it did won't be enough to cause frothyness.

My best suggestion for you is to try a known good accumulator. If you know a fellow TR owner that has a good setup that would allow you to try his, you can make a solid determination if the acc is at fault. If the same thing happens with a known good acc, the problem lies elsewhere.

Z

 

[dentmasters01]

ok, if the acc is leaking, and the car sits for oh lets say 3 days. Should it cycle on and pump up apon initial "key on" for the first time??? Mine doesn't. Another thing. On "pump down" my peddle get hard after only 6 pumps. ??

 

[zeus87gn]

ok, if the acc is leaking, and the car sits for oh lets say 3 days. Should it cycle on and pump up apon initial "key on" for the first time??? Mine doesn't.

It may not initially cycle.....yet. When it's pumped up, it's going to reach a balance in pressure (equilibrium) each time the diaphgram decides it wants to leak. If that balance point is more than the set point of the switch, it wont run. As the nitrogen slowly leaks out of the acc (and into the fluid chamber where you will see it on pump down), there will be a point where it will run on startup.

Remember, this is just my theory thinking you have a pinhole type leak.
That is why I recommended you try a known good acc.
It sounds to me like you acc is slowly dying.

Another thing. On "pump down" my peddle get hard after only 6 pumps. ??

This just adds to the above thoughts. There isn't as much back pressure (nitrogen charge) left in the acc to leave you the reserve you would normally have. If you were to watch it, you will most likely work down to only a pump or two and by then you acc will probably be dead.