what is this and what does it do??

[91gtp]

Ok, Car is a 1991 gp with the 3.4 dohc and 5spd. So everytime i press the brake pedal i hear this noise. it is like a loud humming. Kinda similar to the sound of the fuel pump when you first turn the key, but louder. Also, when i hear that noise the volt gauge goes down about half way then comes back up. And if i hold the brake pedal down, (like at a stop light) i will hear the hum for 2 sec, then it will stop for a couple seconds, then come back. I think i found where it is coming from. its from something on the firewall i think.

It is located a little bit below and to the left of the master cylinder. It has a yellow sticker on it that says something about gas under pressure

another view

close up

 

I also found this thing. it was just sitting on top of my tranny not connected to anything.

 

Anyone know what either of these things are, or what they do. I am trying to get all my problems fixed on this car so it will be a good daily driver.

[Addicted To Boost]

The humming noise you are hearing is most likely your PowerMasterIII brake master cylinder/booster. Some cars came equipped with this special brake cylinder booster. Some are louder than others, but that is most likely what you are hearing.

I just looked at your pics, and you have a PowerMasterIII- that is what is making the noise, no need to worry it is normal.

[91gtp]

is it normal for the volt gauge to fluxuate when the brake pedal is down becuase of the powermaster 3?

[Addicted To Boost]

Yes, it is. When the pump motor runs, it will draw a current in the electrical system, and you will see the drop on your gauge. It will be a much more noticeable drop if your battery is on its way out. The headlights would actually dim when the PMIII pump motor ran on my 90 GP- it had a bad battery though, after I replaced the battery, the dim was less noticeable.

[91gtp]

cool, thats one problem down. thanks

[1990lumina]

That yellow thing is the accumulator I believe.

[Addicted To Boost]

That yellow thing is the accumulator I believe.

Correct.

[GutlessSupreme]

Powermaster 3 brake system info: http://www.kazmotorsports.com/tpsgarage/TGP/brakes/powermaster.htm

 

that other thing looks like the remains of the base of the kickdown cable...? maybe.

[Regal_GS_1989]

Powermaster 3 brake system info: http://www.kazmotorsports.com/tpsgarage/TGP/brakes/powermaster.htm

 

that other thing looks like the remains of the base of the kickdown cable...? maybe.

x2 My guess is that the car was originally an automatic.

[5speedz34]

Powermaster 3 brake system info: http://www.kazmotorsports.com/tpsgarage/TGP/brakes/powermaster.htm

 

that other thing looks like the remains of the base of the kickdown cable...? maybe.

x2 My guess is that the car was originally an automatic.

 

That or my guess, is the remains of a hood cable?

[91gtp]

i suppose either guess could be right. i am going to try to get a hold of the PO and see if he swapped the car over to a 5spd. I know he put a junkyard motor into it so i dont know what else was done.

[5speedz34]

i suppose either guess could be right. i am going to try to get a hold of the PO and see if he swapped the car over to a 5spd. I know he put a junkyard motor into it so i dont know what else was done.

 

Check the RPO sticker on the spare tire cover.

 

Look for the code "M27" that is the Getrag 284. If its printed on there the car is factory 5speed.