Hello all. My father and I recently replaced the wheel cylinders on my 1980 RX-7 GS with rear drum brakes. Normally, the brake line runs to the driver side wheel cylinder, then across the wheel axle to the right wheel cylinder, which has a bleeder valve. However, we couldn't find the left wheel cylinder online, so we replaced the entire OEM brake line along the rear axle in order to accomodate a right wheel cylinder on both rear wheels. We did this by using a T-joint to run hard brake lines to the left and right wheels from the main rubber line. Now, the rear drum brakes are inoperable. We have tried bleeding the system using a vacuum and the traditional two-man method, each time trying to bleed the right and left wheel's cylinders completely, yet we cannot seem to bleed the brakes no matter what we try. We've also taken the proportioning valve apart and put it back together again. It seems to be in good condition. Please advise!Thank you!

 

Is fluid moving through each wheel cylinder's bleeder? Are you using a traditional bleeding method of pump, hold, open bleeder, close bleeder, and pump?

 

Yes and yes. Fluid is flowing through both bleeders and we are bleeding using the traditional method.

 

I'm thinking the brake shoes need a little adjusting. They should be out just enough to get the drum on, too much clearance and they'll feel like they aren't working.

 

The 1979/1980 do not have auto-adjusters. Did you adjust the brake shoe tension after putting the drum back one? The adjuster is on the bottom rear of each backing plate. It's a cammed bolt. The process is in the factory service manual.

Page 11:6 https://www.foxed.ca/rx7manual/manua...(11)Brakes.pdf

http://www.faoxed.ca

 

And there are TWO adjusters on each side; one for the front brake shoe and one for the rear brake shoe. Getting them just right is a bit of a dance, but you'll know you're there when you get good braking action at the rear and don't smell any brake lining burn when you come to a stop. I don't miss adjusting those, as it's done on your back with two wrenches and finesse...

 

Drum shoes are tight against the interior of the drum, but the rear brakes still provide no stopping power. It's a really, really strange issue.

 

Just reread your original post. Thinking about this, I'd go back to the factory configuration. Hope you kept the old wheel cylinder because it can be rebuilt. If not, rockauto has them (https://www.rockauto.com/en/catalog/...+cylinder,1952). When I run into situations like this, I go back to what did I do last.

 

I was wondering why he could only find the left ones .

 

I just checked and Rock Auto lists both left and right wheel cylinders, as well as a few rebuild kit options.

I would also advise going to back to the stock configuration. Take the left wheel cylinder wild card out of the equation. I'm still not sure why Mazda did it theybway they did with only one bleeder but it was for a reason I guess.

 

Issue Resolved!

The problem was a bad seal on the piston inside of the master cylinder. I ended up replacing the master cylinder, and bleeding my brakes one more time. Fixed the problem with my brakes and pedal immediately.

Thanks for all the help everybody!

 

Glad to hear you got the issue resolved! And it's nice to know that using a wheel cylinder with a bleeder on the left rear will work as well.