Installing new master cylinder in 74?
 

Hi Folks.

I have a question regarding putting a new master cylinder into my 74 coupe. The car was missing the entire master cylinder and reservoir. I have installed the reservoir tanks and plastic lines through the car. I am at the point where I need to attach the plastic lines from the tank to the master cylinder itself. What I don't know is which line is the front line and which is the rear? The tank is divided into front and rear sections. It seems that the front section should go to the front part of the master cylinder but it is the smaller of the two sides. Where the plastic lines pass through the body they are oriented left and right rather than front to back. I have the front line from the tank routed through the right side hole in the body.

Does anyone know off hand which way this is supposed to be set up? Can someone take a peek at their non power brake car and let me know? I just want to be sure I am setting this up right.

Thanks a lot, Andy

bump
 

Anyone?

Hmm. I would say that the fronts should use the larger reservoir.

Near as I can tell on my '75 (I haven't had the brake system apart yet), the larger side of the reservoir feeds the front of the master cylinder.

My "guess" would be bigger line for front and smaller for rear.

Have you tried looking for these parts in the Pelican catalog. it might list the sizes for the seperate front & rear.

Look at page 196 of the PET Catalog. It shows the whole diagram of the master cylinder and reservoir tank. It looks like the lines criss-cross just before the MC.

http://www.porsche.com/all/media/pdf/originalparts/usa/911_USA_74_77_KATALOG.pdf

Yes front, (small) is for the rear.

Thanks
 

Thanks,

Seems like the general consensus is that the front part of the reservoir, which is the smaller part, goes to the back of the master cylinder which is for the rear brakes. I will be putting this together this weekend. I'll let you know how it works.


Later, Andy.

Oh, Wait?
 

Well,

I downloaded the PET diagram on page 196 as suggested by Tidybuoy. It shows everything I need, however, it shows that the front part of the reservoir goes to the front of the master cylinder. Maybe I am just looking at the reservoir wrong and the front part is larger. It is really just an internal baffle that separates the two sides. I am leaning towards putting the system together the way this diagram shows.

Any thoughts? Andy.

There won't be any real problem if you connect it the wrong way. Just keep the fluid topped up. The difference in fluid displacement between the front and rear will not be large enough to cause the smaller reservoir to run dry if connected to the front brake circuit. If in fact the two sections are different volumes.

If you run your brake fluid down to where it is below the divider on the bottom of the reservoir, well you have a different problem than deciding which goes to which.

But I can understand your having a problem figuring this out. Most of us who have replaced a MC have done it with lines already in place and aimed at one or the other..

I will take a look at my 74 when I get home in a couple of hours. I will let you know what I find.
Chris

thanks
 

Thanks!

Yundar,
It seems like the PET diagram is correct, if I am looking at it the same way you are.

Chris

All Done!
 

Thanks Everyone!


Got it installed yesterday. Only took me five tries to get everything to fit right.

Helpful hint: Pre install the plastic reservoir lines on the master cylinder and then feed them up through the body with help from your brother. It is really hard to put the lines in first and then try to press them into the rubber grommets on the master cylinder while underneath the car. Also "Uro" brand master cylinder was missing the two little washers that go underneath the rubber grommets so check your new parts carefully.

Brakes bled out just fine. I drove the car up and down the highway for the first time in several years! Yes!

Waiting till Monday to go get license plates and insurance. Will let you know whats next. Andy.