MACH7

I have a brake master cylinder leaking at the rear where it bolts to the booster on a 85 12a. I have already purchased and have the new brake master to install. I can find information about bench bleeding/priming by doing a Google. I have searched the various forms on RX7Club, but I am not finding any that address how best to do the bench priming or my other related questions, thus my posting. If someone knows where on the forum this already covered, I would appreciate being pointed there, since I am not finding it on my own. Or absent that, could somebody who has been through this repair help me figure out how to do it safely and best.

As I understand the process, you put your new master in a vice, making sure its level. Put hoses on the outlets and then insert the other end in the reservoir. Fill the reservoir with new brake fluid. Clamp the hoses so they stay positioned in the reservoir below the fluid level. Then carefully use a Philips screw driver (one suggestion was to wrap the end of the screwdriver with a rag to protect the master cylinder) and slowly push the master piston in, release, then keep repeating until there are no longer any bubbles.

Then move the master cylinder to the car, bolt it to the fire wall, connect the brake lines and then bleed all for wheels, starting with the right rear, then the left rear, then the right front and finally the drivers side front.

Questions:
1. do I have the above correct?
2. the outlets don’t look like they will take a plastic hose, easily, any recommendations for this?
3. any other suggestions?
4. and most importantly, how do I safely get the master from the vice to the firewall, get it bolted on, and the lines fastened without having brake fluid drip everywhere and damage the paint? Note: I did not get any plastic tubing or plastic things to put on the outlets when I purchased the master, which some of the postings I found by doing a Google mentioned came with their master cylinder purchase. Assume the brake fluid will drip from the outlets where the bake lines connect until they are all connected? If yes, how best to deal with the bake fluid leaking problem while getting everything re-connected?
5. and when referencing the shop manual, it says to use a “spanner (49 0259 770A)” to “disconnect the fluid pipes at the master cylinder outlets”. Can you just use a wrench or do I have to buy this “spanner”, else risk damaging the lines/fittings?

Thank you for the help
MACH7
85 12a
85 GSLSE

nobodymv

iTrader: (3)

PM 74RX4. I bet you he has the detailed description as well as numerous pics je can send you!

Siraniko

iTrader: (13)

If you have an air compressor and air bleeder kit, I wont even bother with bench bleeding. I will just bleed it completely to have a fresh brake fluid.

slowautoxr

iTrader: (6)

I just did this job on my street RX-7. Bench bleed the master cylinder and then bleed the brakes as you described.

The only trouble I had was screwing the plastic fittings into the master cylinder for bench bleeding. Put some towels underneath the master cylinder when installing. If you didn't get hoses to fit your fittings - go back to the part store. They should be in the kit.

As far as the wrench goes, use a brake line wrench. The fittings are soft and you will round them off with regular open end wrench.

Good luck.

74RX4

iTrader: (10)

I think you have the suggested method described in your original post. Larger vehicles often need all the steps you've described. I've found 1st gens generally aren't too hard to bleed. On a clutch cylinder I cover the hole for the line with a rag (fluid will spray in your eyes if you don't). Then I fill the reservoir half full, hold the cylinder in one hand and pump the piston with a phillips screw driver a couple times. The brake master has two lines so it is a little harder to bleed this way. Seems like you just have to prime them a little then regular bleeding will finish the job.

I like Wacky's way best.

Here's my version (somebody's that I've stolen). Using the old cap, drill a hole and install a valve stem in it. Use very low pressure from an air compressor with a tire chuck on the end. You can bleed the entire system this way. Open the bleeder valve, attach a hose and put the other end in a container. Fill the reservoir, put on the customized cap, cover with a rag (there's a vent hole in the cap), and gently pressurize the system. Keep the reservoir from draining and keep up the pressure until the fluid comes out clean. You can also just drill a hole and use a blower nozzle and a rag to seal. If you don't have a compressor you can use a garden sprayer (a new one) to supply the pressure. Or just buy a pressure bleeding kit like Wacky also mentioned. If you use pressure to bleed the whole system, its much faster and bench bleeding is not needed. Sorry no pictures

7aull

iTrader: (2)

If you go your vice-route, get a used rubber brake line (the one that goes from the hard line at the fender to the front strut is perfect) and use that to attach to the outlet of the master. This will bend up and into the reservoir to pump the fluid back in. A push-on plastic hose will likely pop off under pressure. Worked for me...

Stu Aull
80 GS
Alaska

MACH7

Thanks for all the information
1. I bought the brake master from a parts store liquidation on Ebay. The make is Bendix. It came in the original box and the master is wrapped in the original plastic that is sealed. There was only the master and attached reservoir, e.g. no plastic caps or tubing for bench priming. Any suggestions where I might obtain those? I can not go back to Ebay, now. I bought it several months ago.
2. I am particularly concerned about brake fluid leaking on the paint, both the fenders and the engine bay. How big a problem is this likely to be, e.g. will the brake fluid drip out while I bolt it to the firewall/booster and connect the brake lines or is the loss of brake fluid so small that a rag will keep the brake fluid controlled? This is a very low mileage RX-7 with original paint that looks new, so I want to make sure I in no way damage the paint.
3. Where can I obtain a brake wrench to prevent damaging the fittings as recommended in the RX-7 shop manual and slowautoxr? Or have you had luck just carefully using a wrench?
Thanks for all the help
MACH7

DriveFast7

iTrader: (1)

1. try your local auto parts store. it's a common item.

2. once you take the master out of the vice, very little fluid will drip out. it won't just pour out. put it in an oil drain pan and walk it over to the car. it will drip a tad while bolting up so put rags all over.

3. i got mine at local parts store. pepboys.com or kragen.com definately use the brake wrench as it grabs the fitting so much better.

Jeff20B

iTrader: (13)

I recently did three clutch masters (three different vehicles) and found that the pinhole in the top of the old cap allows compressed air to be squirted in from a rubber tipped air nozzle. No need to add a tire valve stem.