Hey guys,

I'm really having issues with my brakes!

I just replaced my pads and rotors, and flushed the system. While doing this, it became evident that the Master Cylinder was shot. I'd pump the brake pedal and all that would happen is that the fluid would foam up in the resevoir, and there was no pressure in the lines.

So I replaced the Master Cylinder with a rebuild. I tried to bench bleed the MC, but I don't think I was too successful. (The proportioning valve was still on the car too) I put it on the car, bled the brakes - but they still aren't right. Too much pedal travel, and not hard enough.

So: Is there a way to bench bleed the MC while it is on the car? Do I have to bleed the proportioning valve? I really don't want to have to take it off the car again (PITA), but I can't drive when the brakes are like this.

Thanks again!

 

In the factory shop manual, (Braking System page 11-10) there is a chart that tells you just what has to get bled. It says:

Right Rear Caliper

Left Rear Caliper

Right Front Caliper

Left Front Caliper

Proportioning Valve

Master Cylinder

But it doesn't tell you how to do the MC or The Proportioning Valve. What's the best way?

 

i just did this this weekend and the proprtioning valve was still on the car. With the mc in a vise, i plugged the bottom hole, put the nipple on the 2 front holes and attach the hosses and submerge them in the reservoir with new brake fluid

now push the plunger in with a screwdriver a few time until there is no more air. than switchthe front nipple to the back hole and now plug the front hole. and repeat the plungin process. now take it to the car and install it. you will get a mess everwhere, try and leave in the fittings until you reconnect the brake line. than start bleeding the brakes in this order

p side rear
d side rear
p side front
d side front

this is what i did, and my brakes work awesome now.

 

the MC is the 1st one to bleed. You can do it after install. Just unplug all the brake lines (I think there are 3 of them). Connect the short lines (that came with your new MC) to the MC and dip the other ends into the resevoir. Now, pump the brake slowly to get all the air out. That's pretty much it.

For the proportioning valve, you probably need a helper (to sit in car and hold the brake pedal down). Hold the pedal down. Open the brake line fitting (one that goes to front, one that goes to back) at the valve to let air out. Close fitting and release brake pedal.

then you do the usual sequence at the wheels.

IF you don't want to mess around with all this, you can go to a place where they have a pressure bleeder and let them do it (it's much easier that way)

Hope this helps,
Hugues -

 

OK, that sounds kind of like what I did, but I'm sure that I didn't get all of the air out of one of the holes - and I didn't even do the proportioning valve.

Now, how did you plug the bottom hole? I got 4 plastic nipples in the kit - and all 4 have holes in them.

Do I need to bleed that bottom hole too?

Thanks a lot guys!

 

I am not sure I follow what you're saying but ...

if the MC has four "holes", then you connect all 4 with the short lines (that came with new MC)and dip the other ends (of the short lines) into the reservoir (At the same time ... don't need to do them 1 by 1)

Hugues -

 

Ohhhh Ok. I got a bit confused there. I'll give that a whirl and see just what happens.

I'm assuming that the P-Valve should be done the same way, right? put the nipples on the "out" holes, and pump the brakes 'till the air is gone. Do this after the MC, and once it is done, do the brakes.............. again.

Sorry for the confusion - but people around here have been telling me all kinds of **** about how to and how not to bleed the MC! Everyone I talk to has a different opinion - but they also say "but I've never done it on an Rx-7". So thanks for all the experienced help!

 

what is the p-valve what does it look like

 

I'd rather do it like you do it at the wheels. you know: close fitting, keep brake pedal down, open fitting, close fitting, etc
but it may be ok if you connect a short line from the fitting to the MC reservoir and do it the same way as the MC.

then you've got to do the 4 wheels in order.

Hugues -

 

If you don't have a prop. valve, then the front brakes do all the work and will lock pretty fast since that's where the weight is transferred when you brake.
The p-valve enables the rear brakes to get a piece of the action, if you will (prevent an early locking of the front brakes)

It's located right next to the MC on the booster.

Hugues -

 

Great, Thanks a bunch Hugues!

I did the brakes in the right order without a problem, but when there is air in the MC, it kind of defeats the whole process!

 

yea i got one..thats what i thought it was but i wasnt sure


thanks alot

 

Close, but not quite.
When you brake, weight is transfered forward, with 70-80% of the weight on the front tyres. Because the rear end is now so light, if you were braking the rear wheels as hard as the front ones they'd just lock up. The proportioning valve reduces the fluid pressure sent to the rear brakes to stop this happening.
So the proportioning valve is there to stop the rear wheels from locking up, not the front.

 

Thanks for the correction NZ

Hugues -