Quick question?

[BUICKGNX]

Hey guys,
I am in the process at this time of installing a new OEM pump motor for the "lovely" power master cylinder. The instructions that come with the new motor for bleeding are as follows.....
1. Fill the reservoir
2. remove brake line connectors from master cylinder. This i understand. This is located on the actual unit.
3. This part is confusing. It says have someone in the car press brake with no power assist and then tighten forward brake line connector. Then it says that you are suppose to release pedal slowly. After 5 seconds, reapply brake pedal and hold. OPEN FORWARD CONNECTOR 1/2 TURN TO PURGE AIR FROM CONNECTOR. TIGHTEN CONNECTOR. WHERE IS THIS FORWARD AND REAR BRAKE LINE CONNECTOR. IS IT LOCATED ON THE POWER MASTER UNIT.DO I NEED TO TAKE TIRES OFF THE CAR OR NOT??
pLEASE LET ME KNOW. NEED HELP.

THANKS GUYS

MICHAEL

 

[Turbo6inKY]

Exactly as it says. You loosen the forward brake line nut and have your buddy step on the pedal. This pushes the air out of the master cylinder.

 

[salvageV6]

Yes on the master cylinder itself.

 

[gofstbuick]

Just finished rebuilding my powermaster unit. The instructions are asking you to bleed (basically bench bleed) the master cylinder. Then you fill the larger third reservior. This (reservior, closer to the passenger side) is the powermaster motor reservior. Fill it as high as it will go and then turn the ignition on. The powermaster motor will begin drawing brake fluid in, until the the system is purged of air. The forward hole at the bottom of the powermaster reservior is the suction side and the hole in the rear is the return port. DONOT let the motor run for more than 20 seconds and if the reservior runs dry, then add more brake fluid. If the motor stops and begins a low hum, you have air in the system. Then you'll need to turn the ignition off and loosen the brake hose (just below the accumulator) until brake fluid begins to flow (DONOT completely remove the hose fitting) and allow it to gravity bleed. This is the check valve for the powermaster and air can get trapped in that hose.

 

[BUICKGNX]

Thanks Gofstbuick.
Guys, you are really helping me out. 1 more question. The 2 other brake lines that are on the power master cylinder....Do they need to be bled as well as the other line located under the accumulator?

Please let me know

Thank you kindly!!
Michael

 

[gofstbuick]

The two brake lines on the master cylinder (that are on the same side as the accumulator) are for braking. The front line is for rear brakes and the rear line is for the front disk brakes. You should use a bleed kit to bench bleed the master cylinder. It consist of plastic fittings, hose and a metal s-clip that will hold a hose in the coresponding reservior. You can probably get the master cylinder bleed kit from any local parts house. DONOT fill the powermaster motor reservior until the master cylinder is bled. Before installing the brake lines, install the plastic adapters and connect a hose to each adapter. Use the metal s-clips to hold the the hose in the reservior. Fill the two small reserviors (closes to the drivers side) with brake fluid. Hop in your car and slowly press the brake pedal down and release. Do this three or four times. The fluid should alway be clear and shold not foam. The movement of the pedal (while the hose is dipped in the brake fluid in the reservior), will push brake fluid out when you press the pedal down and suck fluid in when you release the pedal. This gets the air out of the master cylinder. Once you bleed the master cylinder, connect the two brake lines and apply the brakes. You should hear the front and rear brakes being applied. Now fill the powermaster reservior and begin the procedure from the previous discussion.

 

[BUICKGNX]

Thanks for the reply Gofstbuick. I am actually changing the pump motor with the actual unit still in the car. I sucked out all the brake fluid out of the reservoir with a turkey bastor, cleaned the reservoir with clean towels. I am going to change motors tonight and add new brake fluid (GM Dot 3). So you are saying that i should only fill with key off the 2 ports closest to the drivers fender with fluid and then bleed by unscrewing the 2 lines 1/4 turn and bleed. The fluid should come out clean without bubbles. If there are bubbles, there is air in the system. Do i have to unscrew the other line that is located under the accumulator?
This is my first time doing this and would like to do it right. The pump motor in the car now looks to be original along with the fluid.
Please let me know

Thank you for your time

Greatly appreciated

Michael

 

[gofstbuick]

Additionally, I hope you are using a fluid resistent fender cover over a clothe fender cover. If brake fluid comes in contact with a painted surface, it will bubble the paint. I drape a clothe fender cover on the fender and drape a fluid resistent cover over the clothe fender cover. I was not sure I got all the air out of the master cylinder, so I had to loosen the brake lines and have someone push on the pedal. I used a rag to cover the lines, but brake fluid shot past the rag towad the fender. It hit the fluid resistent fender cover and I just wiped it up. If I wasn't using that type of fender cover, the car would have to be moved outside for an immediate wash.

 

[BUICKGNX]

Hey Gofstbuick,
I am using tons of towels, plastics, etc....to cover the motor, inner fender, etc.. Some fluid as i bled dripped on the inner plastic fender, but no big deal. I wiped immediately and will clean the car completelty when i finish this project. So does it soud right in what i am doing??

Thanks

Mike

 

[gofstbuick]

If you're just changing the motor, then donot disturb the two front brake lines. If you didn't loosen the brake front brake lines, then the brake system should be free of air. Just install the motor and follow the procedure for the larger (motor) reservior. This master cylinder is broken into three parts. The two reserviors (closes to the driverside fender) is for braking and the larger reservior (closes to the passenger side) is for powermaster power assist (takes the place of the power brake booster (vacuum system) or hydraulic booster assisted (by power steering pump) Hydroboost system (hot air cars).

 

[BUICKGNX]

A few days ago i did loosen the 2 lines that are in front. Will it affect anything? You are saying that the only line that i should disconnect to bleed is the rear one that is located under the accumulator. Need mor einfo pal

Thanks gofstbuick

Michael

 

[gofstbuick]

If you click on email, you're more than welcome to email me. I'll probably get notified quicker. But yes, it sounds like you're doing okay.

 

[BUICKGNX]

Thanks pal. I'll keep you posted. Iwill email you if i need any help. Thank you kindly.

Michael

 

[gofstbuick]

Since you loosened the two front brake lines, did you step on the brake pedal with the lines loosed? If not, the system should be free of air. Just set the motor up and start the motor purge process. Once the motor section is filled, don't step on the pedal without the reservior cover being in position. The return port of the powermaster motor will blow brake fluid everywhere.

 

[gofstbuick]

If the new motor runs and doesn't stop, then this is what probably burned up the previous motor. I ordered a master cylinder rebuild kit from GM. What I found was that the seal to the check valve was severed. If you haven't changed brake fluid in a long time, there will be a bunch of black gunk on the power piston assembly, in the cylinder bore and in the reserviors. It needs to be cleaned with denatured alcohol or brake clean and re-assembled. Very simple job. The hardest part is removing the snap retainer and check valve assembly. Just make sure you position the check valve with the spring facing the master cylinder body. I accidently put it in backwards and had to take the assembly apart twice, before I figured out what I did wrong. After rebuilding the master cylinder, the car stop great.

 

[BUICKGNX]

Hey Gofstbuick,
Thanks so much with your help. Are you attending the gs nationals this year? Maybe we will meet. Take care...I'll keep you posted.

Thank you kindly

Michael

 

[BUICKGNX]

Just remembered,
When i bleed the line for the new pump motor, do i need to take off the accumulator. I installed a new accumulator and switch. The pedal is hard right now with the brake light on always. I will change the motor tonight with the brake power master cylinder mounted under the hood.
Please let me know

Thanks pal!

Michael

 

[gofstbuick]

With the system pressurized, DONOT attempt to remove the accumulator or pressure switch. The accumulator is split into two cavities. One side is pressurized with nitrogen and a diaphram retains the nitrogen. The pump starts and pressurizes the accumulator and pushes against the nitrogen filled diaphram. The pressure switch senses pressure and turns the motor on and off at specific pressure readings. The pressure can exceed 750psi. When you press on the brake pedal, the nitrogen diaphram pushes the pressure to provide power assist. THERE IS A WARNING (ON THE ACCUMULATOR) TO APPLY THE BRAKES AT LEAST 10 TIMES (WITH AT LEAST 50 POUNDS OF FORCE) BEFORE REMOVING THE ACCUMULATOR. THIS RELEIVES THE PRESSURE IN THE SYSTEM. IF YOU ATTEMPT TO REMOVE THE ACCUMULATOR WITH THE SYSTEM STILL PRESSURIZED, IT WILL SHOOT OFF LIKE A ROCKET, REMOVING DIGITS, HANDS OR WHATEVER IS IN IT'S PATH. THE PRESSURE SWITCH CAN FLY THE SAME WAY. The precharge pressure of the accumulator is between 200-330psi, below that it drops to zero. When the accumulator goes bad, the pedal gets hard, because there is not enough pressure to maintain power assist. Also, if there is no pressure in the system, the pedal will get hard. The brake fluid is sucked out of the reservior and into the motor and accumulator and returns once the pedal is depressed. If the motor is not running, the fluid will return to the reservior through the rear return port, otherwise it keeps cycling to maintain pressure for power assist braking. This is also the reason it says not to overfill the master cylinder. You could probably get away with overfilling the brake reserviors of the master cylinder (two smaller cavities closes to the drivers side fender), but not the powermaster side. If you did and you depressurize the system, brake fluid will over flow into the engine compartment if it can overcome the reservior cover.

 

[BUICKGNX]

Hey Gofstbuick,
Thanks for the reply. Would it be wise to take the accumulator off when bleeding the line for the motor. How can i get to the nut when the accumulator is in the way. The brake system is depressurized (hard brake pedal) I also was thinking about purchasing the rebuild kit. Is it easy to do. What steps are involved?

Thanks

Michael

 

[gofstbuick]

The torque is only 13 foot pounds, so a 17mm box wrench should be able to reach below the accumulator.