? on soft pedal on PM install-brake pedal rod?

[tim87tr]

My PM motor went bad and I installed a low mile complete PM system. The brake pedal rod seems loose after I attached it to the pedal and the pedal is completely soft, and I started to bleed the system which didn't help either. Does this rod attach internally in the master cylinder body area and has snapped of place. I may need to pull the system off again and reset the brake pedal rod? I also want to say this brake pedal bolt was a real PITA to "disconnect/reconnect"

 

[turbofish38]

The rod is held onto the MC with an internal clip. IIRC its a PITA to get off. You say it feels loose on the pedal. Stupid question? Are you using the vacuum pedal with the PM. The pin diameter is different between the two. It is possible to use the PM rod on the vacuum pedal but not vice-a-versa. Also there are two diffrent PM rods. One G-body which can be ID'd by the letter "G" or "A" stamped on it or B-body which has the letter "B" stamped on it. They are a tad different in length.

 

[zeus87gn]

As the pedal rod issue has been addressed, what do you mean by soft? Is there any resistance at all in the pedal and is with with or without the system pressurized?

IMPORTANT QUESTION: Did you 'bench bleed' the master cylinder portion of the power master before you bled at the wheels? If you didn't, you have air in your system. #1 cause of a soft pedal.

 

[tim87tr]

Hey Guys, thanks for the response. It is a low mile GN specific PM system, but I didn't bench bleed the master cylinder. I just noticed I have instructions for bench bleeding for the vacuum kit I have, but I had an extra PM so I was swaping it since I had a new accumulator anyway.

I'm not looking forward to pulling the rod off the pedal and reinstalling that. The rest is not bad.

 

[tim87tr]

As the pedal rod issue has been addressed, what do you mean by soft? Is there any resistance at all in the pedal and is with with or without the system pressurized?

IMPORTANT QUESTION: Did you 'bench bleed' the master cylinder portion of the power master before you bled at the wheels? If you didn't, you have air in your system. #1 cause of a soft pedal.

I have a couple extra cut-off lines for the purpose of bleeding the MC, but I could not get it to "prime", and already had it on the car. It is possible that the spare PM system has a bad motor also, but I have another one to try. I also have a vacuum replacement but wanted to try the PM first. Any suggestions on something I might be doing wrong?

 

[zeus87gn]

I have a couple extra cut-off lines for the purpose of bleeding the MC, but I could not get it to "prime", and already had it on the car. It is possible that the spare PM system has a bad motor also, but I have another one to try. I also have a vacuum replacement but wanted to try the PM first. Any suggestions on something I might be doing wrong?

There are two sides to the P/M. The accumulator (high pressure) with the pump & motor, and the standard side with the brake lines to the wheels. They must be dealt with individually.

'Bench bleeding' is a term to describe a method of air removal for the standard side. It can be done on the car and is actually easier because you use the brake pedal to work the cylinder. Use your lines to route the fluid back into the bowl so as not to loose a ton of brake fluid and the air will work out as you work the pedal. You should get the idea as you see it work. Do this with the acc ball de-pressurized.

What are you trying to prime...the motor? It should pump up almost immediately, and the accumulator in just a few seconds. How long is it taking? Dont let the motor run more than 20 seconds at any given time. The pump hose fitting at the cylinder can be cracked loose ever so slightly to help the motor get pumping. You may have to cycle the accumulator a couple of times to get all the air out.

There is a lot too it, I hope to have the full procedure written by the holidays for all to see.

 

[tim87tr]

There are two sides to the P/M. The accumulator (high pressure) with the pump & motor, and the standard side with the brake lines to the wheels. They must be dealt with individually.

'Bench bleeding' is a term to describe a method of air removal for the standard side. It can be done on the car and is actually easier because you use the brake pedal to work the cylinder. Use your lines to route the fluid back into the bowl so as not to loose a ton of brake fluid and the air will work out as you work the pedal. You should get the idea as you see it work. Do this with the acc ball de-pressurized.

What are you trying to prime...the motor? It should pump up almost immediately, and the accumulator in just a few seconds. How long is it taking? Dont let the motor run more than 20 seconds at any given time. The pump hose fitting at the cylinder can be cracked loose ever so slightly to help the motor get pumping. You may have to cycle the accumulator a couple of times to get all the air out.

There is a lot too it, I hope to have the full procedure written by the holidays for all to see.

It might be possible that the accumulator is pressurized, so I might just crack it with something around it due to the pressure. I had it off when I put on the new PM, but not sure the PM motor ran to repressurize. I actually don't hear the motor run at key on, so I might have a bad motor on the replacement PM. I'll try cracking that line at the cylinder to get the motor running as I forgot to do that. The MC is not priming with the pedal at this point.

Any update on the procedures?

 

[zeus87gn]

It might be possible that the accumulator is pressurized, so I might just crack it with something around it due to the pressure. I had it off when I put on the new PM, but not sure the PM motor ran to repressurize. I actually don't hear the motor run at key on, so I might have a bad motor on the replacement PM. I'll try cracking that line at the cylinder to get the motor running as I forgot to do that. The MC is not priming with the pedal at this point.

Any update on the procedures?

Your motor isn't running when you turn on the key?! Only time that should happen is when the fuse is blown or the motor just 'clicks' after depressurize. If it just clicks, your accumulator is bad...motor is dead-heading. If the motor doesn't do anything, you need to determine if you have power to it. Then you may be into electrical problems.

Don't crack anything loose without pumping the pedal 10 times first! If it is under pressure, you don't want brake fluid flying around at 600psi!!

Procedure is coming along. Got to check a couple of things first before I release it to the public.

 

[tim87tr]

Does it take quite a bit of pedal pumping to get the MC to prime? I had my son move it approx 25 pumps, but nothing yet. I did crack the accum ball to depressurize it, so I guess that is a good thing because my PM motor must be working.

 

[zeus87gn]

Tim,
Please explain to me what you mean by 'prime' (I want to be sure I understand what you are doing before I can give you the right answer):

Are you trying to bench bleed or just bleed at the wheels?

Are you trying to pressurize (pump up) the accumulator?

You don't depressurise (pump down) the accumulator by cracing it loose. That's dangerous and can blow an oring apart. You pump it down by pumping the pedal at least 10 times with the ignition key off.

 

[tim87tr]

Tim,
Please explain to me what you mean by 'prime' (I want to be sure I understand what you are doing before I can give you the right answer):

Are you trying to bench bleed or just bleed at the wheels?

Are you trying to pressurize (pump up) the accumulator?

You don't depressurise (pump down) the accumulator by cracing it loose. That's dangerous and can blow an oring apart. You pump it down by pumping the pedal at least 10 times with the ignition key off.

Yes, I can't get the MC to "bench bleed" and it is on the car. I wanted to do this first then bleed at the wheels after I got the MC primed. I did pump the pedal to depressurize the accum ball prior to removing it, but I think since the MC is not primed, it was still under pressure. I've taken them off before and depresurrized them, but this one still had pressure when I removed it, but I had a shop rag around it, no problem. I was just commenting that my pump must be working if the accum ball was pressurized.

 

[zeus87gn]

Ok, I understand what you are talking about.

When your son presses the pedal, the return lines you should be using will be pumping something (barring a major malfunction). It may be large slugs of air at first, but after a stroke or two it should be mostly fluid.

Lets make sure we are looking at this the same...
1 - The return lines are fed from the line ports back into the bowl
2 - The d/s of the bowl is full of fluid (this is all you need to be concerned with for bench bleeding)
3 - The acc ball is in place only pumped down (depressurized)
4 - Are you holding the return lines in the bowl fluid so the cylinder doesn't suck air back into them when you release the pedal?

If the pedal is being moved almost full stroke, it should be moving fluid. Only thing I can think of is maybe the pedal isn't being stroked fully?

 

[tzque]

I had some problems before switching to vacumm . Taking off the MC is quick . bench bleed it and then bleed your system . I have done it without bleeding a Mc but it just seems better when I do . The soft petal is an indication of air in the line . If you dont want to take it off , which I would do first, rebleed everything .my petal was soft because of air in the left rear.

 

[tim87tr]

back at it

I finally swapped out the other PM replacement and found the shaft that goes into the MC had popped out. I had another PM, put it on, did the bench bleed with the pedal attached, which worked this time, but have not been able to get the PM motor to quit running.

I did depressurize the accumulator and then disconnect the booster tube and nut assembly from the casting boss at pump outlet per gnttype instructions, which allowed the brake fluid to gravity bleed from the disconnected end of the tubing. This did not help with the PM motor to quit running, nor did normal bleeding procedures for the brake system.

Any ideas?

 

[tim87tr]

Update!!

I got the car out and drove it up the driveway a bit. It has exhibited the same symptoms with the new PM as it did when it originally failed, and LOCKED UP the brakes. The pedal became very stiff and the brakes are starting to lock up again.

I really have looked at the gnttype board troubleshooting, but it is of course confusing. I think I need to disconnect the booster tube at the pump outlet to relieve this pressure, but I went through the master cylinder bleeding procedures before I took it out, and the MC seemed to prime ok on the bench bleed. So I guess it may be the accumulator or one of the sensors/switches? The pump never stops running and then the brakes start to lock up eventually. I am at a loss here, please help

 

[tim87tr]

replying to my own question

I think I made it through the diagnostic flowchart on gnttype. I believe it is the accumulator, as when I disconnect the pressure switch, the light goes off. Then I go through the rest of the flow chart and the darn motor still runs more than 15 seconds. I thought I bought this Kirban one used, but may need to buy another new one somewhere. Any place have them in stock?

 

[zeus87gn]

Tim,

Sorry, I lost my subscrption to the thread somehow.
Do I understand you that you are trying a USED accumulator?
Not a good idea, although it is a 50/50 shot in the dark if it is good.
Anyway, Kirbans has them in stock. I have heard that he has them on his ebay sale a little cheaper than if you call him, but don't know for sure.

You brakes are locking up? The rears or the fronts?

 

[tim87tr]

Tim,

Sorry, I lost my subscrption to the thread somehow.
Do I understand you that you are trying a USED accumulator?
Not a good idea, although it is a 50/50 shot in the dark if it is good.
Anyway, Kirbans has them in stock. I have heard that he has them on his ebay sale a little cheaper than if you call him, but don't know for sure.

You brakes are locking up? The rears or the fronts?

Hey thanks for the reply!

I bought a Accumulator used from someone I think last year, but it had the yellow sticker and made in Germany just like the Kirban one. I think that is the problem and ordered a new one from Kirban this morning. I'd already swapped out MCs so that wasn't it, although my stock PM system motor was failing, so it needed replaced anyway.

It is for sure at least the rear brakes locking up because the car won't even turn them over. I drove up and back on the driveway twice until they started to grab, I guess from the pump continuing to run. I unplugged the pressure switch, and the pump did not run, the light went off, and I went through the flow chart and the pump still runs for over 15 sec, so hence the new accum on the way.

Thanks for the help. Does it sound like accumulator to you?

 

[zeus87gn]

Please clarify your statement "the pump continuing to run".

Does this mean it never shuts off at all? According to my manual, if the pump runs more than 15 seconds, the pump/motor is failing.
Or just running longer than 7 seconds to shut off? With that old acc, I would understand this. Kirbans new acc's are a new design. It won't look like the one you are dealing with now.

The pump running will have no bearing on wheel lockup. There is a seal between the high pressure side of the P/M and the standard side. If that seal (oring) is blown in the m/c, the pump recirculates fluid back into the p/s of the bowl and you can detect it when the pump is running. This is not the cause of the wheel lockup problem.

If you pump bled your wheels, you may need to check the state of the plunger in your proportioning valve. It can cause trouble. If it is as it should be, you may have a mechanical problem in your rear brakes. I have heard that sometimes old rubber lines will internally swell and not release pressure.

 

[tim87tr]

Please clarify your statement "the pump continuing to run".

Does this mean it never shuts off at all? According to my manual, if the pump runs more than 15 seconds, the pump/motor is failing.
Or just running longer than 7 seconds to shut off? With that old acc, I would understand this. Kirbans new acc's are a new design. It won't look like the one you are dealing with now.

The pump running will have no bearing on wheel lockup. There is a seal between the high pressure side of the P/M and the standard side. If that seal (oring) is blown in the m/c, the pump recirculates fluid back into the p/s of the bowl and you can detect it when the pump is running. This is not the cause of the wheel lockup problem.

If you pump bled your wheels, you may need to check the state of the plunger in your proportioning valve. It can cause trouble. If it is as it should be, you may have a mechanical problem in your rear brakes. I have heard that sometimes old rubber lines will internally swell and not release pressure.

It could be the a mechanical problem with the rear brakes. I do have the S10 wheel cylinders, but never had trouble with them over the years. I have a new Kirban accumulator on the way, and the one I have was I believe a used Kirban since it has the same yellow sticker and stampings. It sounds like I may need to send it back. When I followed that diagnosis flowchart, it appeared that the accumulator was the problem.

I have swapped two additional PM units onto the car. The first that I had trouble with was because the brake pedal rod had popped out the the socket in the MC, and I wasn't able to bench bleed with the pedal. The second one I was able to bench bleed fine. So I think I have eliminated anything with the MC since I've had two on there and the pump ran non-stop and the light stayed on.

I will check the prop valve also. I did pump bleed the brakes, I have one of those vacuum pumps that draws fluid out. I do have a line lock, and may just remove it temporarily to see if it is causing a problem. I'll go out and check a few things again.