looking for some technical help....

[Joe Fieroshop]

Hi guy's,   Not sure if anyone can help me with a problem i'm having. I'm working on a 1989 Cavalier Z24 installing a 11.25" brake upgrade front and back. I need to change the master cylinder with a larger piston bore, the problem is this car has 4 brake lines coming out of the master cylinder. Two for the front and two for the rear, does any one have access to some kind of book that have pictures and dimensions of all the GM master cylinders that they make. I know with the Fiero we use one from a Blazer/Jimme but it only has two ports. Any help would be greatly appriciated please contact me by e-mail (racetek@idirect.com) P/M or by phone 416-747-5728.

Thanks
Joe

[fiero308]

well here is some info; (quoted)

it will at least explain what you have there....

"the delco compact master cylinder is designed for use in a diagonal split system.  The left front and the right rear brakes are serviced by one piston and the right front and left rear are served by the other.

It incorporates the funcitons of a standard dual master cyl with the proportioning valves built in.  In addition, a quick take-up feature is incorporated which provides a large volume of fluid to the calipers and wheel cylinders at low pressure with initial brake application.  The low pressure fluid quickly provides the displacement requirements created by the seal retracting pistons into the front calipers and spring retraction of the rear drum brake shoes.

A separate plastic reservoir is mounted to the master cyl and supplies brake fluid to both the front and rear pistons.  A fluid level sensor is installed in the reservoir.


don't know if that helps but that is all I could find.  Sounds kinda thorny/unfriendly to me....
Maybe try one of the cavalier (J body?) chatrooms?

[2ML67]

Pontiac 6000's also used that type of master cylinder even on the heavy duty braked cars. Might be usable for you. Dan

[Joe Fieroshop]

Pontiac 6000's also used that type of master cylinder even on the heavy duty braked cars. Might be usable for you. Dan

Dan, do you have a year that I can go by when i'm ordering it?

Fiero308 thanks for the info, do you think the built in porportioning valves have anything to do with a very soft pedle, with the car off and a new master the pedle has some resistance. When the car is running the pedle goes right to the floor, as if you has fluid loss. No resistance at all? I did mention i replaced it with a new one and still same thing. This car is driving me insane, i did another Cavalier three weeks a go, the same year 89 and i changed all four calipers and it's fine, no problems stops on a dime  .

Maybe some one with a fresher head can see what i'm missing or doing wrong?

Thanks
Joe

[aaron88]

Could be a seal in the master cylinder if it's not air in the system somewhere.

[fiero308]

I'm pretty sure the new master has to be bench bled? There is a procedure for it; you need to buy some cheap but special fittings etc.

 Not 100% but I think so.
But I am sure you would know that.........