Excuse my ignorance, but what function does the metal brake hydraulic part next to the master cylinder serve? I have a good understanding of the master cylinder itself just not sure what the other part is or does.

The right front brake line is connected to it and the rear brakes are also connected. Why aren't those lines just connected directly to the master cylinder?

Thanks!

 

Figured it out on my own actually, it's the metering valve. It causes the rear brakes to engage first by not pressurizing the front brakes until a certain amount of pressure is applied to the rear hydraulics.

 

The valve you speak of actually serves 3 different functions , ( 1 ) .. when there are disc on the front and drum on the rear the disc on the front pads actually touch the brake caliper ( The rotors on most cars are a tiny bit out of true so when the brakes are released the rotor which actually has a tiny wobbles to it pushes the brake pads back enough to release the brakes.) and the rear shoes return with springs so there is no drag on the rear .. So the valve keeps a small amount of fluid in the front system while relieving the total pressure in the rear .. ( 2 ) .. when the brakes are applied being as the rear shoes are fully retracted they need a little extra fluid to start the braking procedure ..so the valve allows a little extra to the rear brakes . now being as the rear brakes would lock up first if equal pressure was applied to front and rear brakes at the same time . ( Because there is far more weight on the front than the rear during normal braking the valve regulates the pressure between front and rear to keep the rear brakes from locking up and also helps control nose dive on the front end during agressive braking ).. ( 3 ) most but not all valves have a equalising switch that activates the brake warning light on the dash ( it simply slides one way or the other grounding out on a centre pin and lighting the brake warning light ,when there is a failure of pressure in either front or rear systems ). So that little valve is actually a brilliant device doing many functions at the same time .. I hope I havent confused you ..

 

true but not really and it gets confusing most of the time. I have used FB master cylinder in my RX-3 but I placed a plug in the bottom port and ran a line from the other port to a stock RX-3's brake line "wye" (this is where it split to left and right brake. no issues or whatsover.

 

The issue you would have there is when you come to a stop at a red light you will feel the rear end of the vehicle settle down and the front end will lift both front and rear are getting the same pressure ,, where as the proper way the valve regulates the fluid so the rear brakes work to their maximum protential with locking up .keeping the vehicle from lifting in the rear and at the same time keeping the vehicle from diving in the front THAT IS WHY THEY ARE MADE AND INSTALLED IN THE SYSTEM . try it next time you stop at a light you will feel the car give a bouncing feeling after it has come to a complete stop almost a feeling of trying to relax itself.. You might not notice this now but if you fixed it to work proper you would notice the difference right away ..

 

you must have drum brakes in the rear, not disc brakes

 

I know this is really old thread but I have a problem. I have a series 1 and upgraded to the T2 brakes. I ordered the MC from a series 3 for disks and had it ready to go. First problem was the lines wouldnt work on the S3 because they were in the wrong locations. Then came the real issue, I was robbed and they theifs made off with both of my Mc's. Now, I have a brand new MC for a series 3 but the valve isn't around. I been trying to locate the valve but no one has it. I tried black dragon, mazdatrix and even autozone. Where do I get one and if it has to be used do these go bad?

Thanks
shawn

 

used is ok, its basically a ball and spring in there, and if it was bad nobody would ever know anyways!

or you could get an aftermarket adjustable one like Jack has https://www.rx7club.com/race-car-tech-103/brake-proportioning-valve-931953/