1991 Beretta v6 master cylinder

themixer · Post by **themixer** » Mon Mar 10, 2014 1:19 pm

Does anyone have access to a picture with the labels?

Just want to be sure that I reassemble with the new lines properly!

Post by **Cliff8928** » Tue Mar 11, 2014 3:38 am

You can't do it wrong on the older models, all four fittings are unique.

themixer · Post by **themixer** » Tue Mar 11, 2014 6:30 am

I have cut all the factory ones off and am bending custom ones

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woody90gtz · Post by **woody90gtz** » Tue Mar 11, 2014 8:31 am

It's an odd setup:

http://www.v6z24.com/jbodyforum/brake-l ... brake.html

themixer · Post by **themixer** » Tue Mar 11, 2014 8:43 am

cool i did it last night and that's what i guessed was correct thanks for the info!

Post by **3X00-Modified** » Tue Mar 11, 2014 8:52 am

Wait really?!?!? the top and bottom are are split between rear and front??? I would have expected the fittings toward the front of the master to be for one end and the ones toward the back to be for the other end of the car... Due to the fact that the master is a dual piston setup providing different flow rates to each end of the car.

I have to verify this on my car when I get home but I just cant believe that one.

Nevermind... found a print out... Orientation is weird on the top image... for reference your looking at the underside of the car from the right front corner of the radiator support area.

That's F-ed up...

woody90gtz · Post by **woody90gtz** » Tue Mar 11, 2014 9:07 am

Yeah, it is weird, but when you take it apart you can see why. There are secondary springs and valve to change the pressure of the rear lines. Here are a few pictures of the Lumina master swap I did.

Post by **3X00-Modified** » Tue Mar 11, 2014 9:17 am

I still need to do that.

Rettax3 · Post by **Rettax3** » Tue Mar 11, 2014 3:39 pm

?? Another potential upgrade I don't know about??

Why is the Lumina M/C an upgrade?

Post by **3X00-Modified** » Tue Mar 11, 2014 3:50 pm

It has a different bias setup for the disc/disc vs the disc/drum that a Beretta has.

Rettax3 · Post by **Rettax3** » Tue Mar 11, 2014 4:59 pm

3X00-Modified wrote:It has a different bias setup for the disc/disc vs the disc/drum that a Beretta has.

Okay, gotcha. I guess I either forgot or didn't know that both you and Woody had completed the disc-brake swap... Probably not something I will be worried about anytime soon then. Whew!

Post by **Cliff8928** » Wed Mar 12, 2014 4:11 am

woody90gtz wrote:Yeah, it is weird, but when you take it apart you can see why. There are secondary springs and valve to change the pressure of the rear lines.

I believe this has to do with the diagonally split braking so that you can have somewhat stable brakes in case of a line failure.

GM wrote:The master cylinder for this vehicle is a composite design which contains a plastic reservoir and an aluminum body. This design is used in a diagonally split system. One of the front and one of the diagonally opposite rear brakes are served by the primary piston. The opposite front and rear brakes are served by the secondary piston.

The master cylinder incorporates the functions of a standard dual master cylinder. The master cylinder has a fluid level switch and integral proportioner valves. The proportioner valves are designed in order to provide a better front to rear braking balance during a heavy brake application.

1988GTU · Post by **1988GTU** » Wed Mar 12, 2014 7:52 am

And that design has saved me in such said event.

Unlike ABS.

woody90gtz · Post by **woody90gtz** » Wed Mar 12, 2014 12:52 pm

Agreed, Cliff. And it has the proportioning built in. My test showed 1450psi front and 950psi rear for the Lumina and 1450f/500r for the Beretta master IIRC.

Rettax3 · Post by **Rettax3** » Thu Mar 13, 2014 1:37 am

woody90gtz wrote:Agreed, Cliff. And it has the proportioning built in. My test showed 1450psi front and 950psi rear for the Lumina and 1450f/500r for the Beretta master IIRC.

That lower operating pressure for the drums helps to explain why my old Plymouth with all-wheel drum brakes doesn't even have a brake-booster. That and the fact that they wanted the car to weigh as little as possible while still getting a big-block dropped in under the hood...

But I am way off topic here, sorry.

It does make me wonder if the rear hoses need to be upgraded when converting to all-wheel disc on the Berettas though...

Beretta.net