14 replies to this topic

[Richard Pressman]

Mazda's parts catalog shows what appears to be an "O" ring which goes between the brake master cylinder and the power booster. The part is included in the sub-assembly picture but without a p/n. I called a dealership this morning and they told me the "O" ring is included as a part of the master cylinder and is not available by itself.

Since the only replacement I could find at Mazda Motorsports is a re-manufactured one I sourced a new one elsewhere. Of course it came w/o any gasket or "O" ring.

Anyone got a lead on where to get that part number, part, or even if it's needed? Would a smear of RTV do just as well?

On my new master cylinder where the mounting flange butts up against the cylinder body there is a shallow groove machined into the part which looks like it would accept an "O" ring very nicely.

Haven't done a master cylinder replacement before. Any help welcome.


---Oh, do you all mess with setting or re-setting the activating rod on the booster or just bolt on the new cylinder and go?


Thanks.
rjp

[red986s]

Might be able to source it from McMaster-Carr.

http://www.mcmaster....o-rings/=dlpw3n

[Richard Pressman]

Already checked M-C. Too many choices. I'd like to try to get the "real" one before guessing about thickness, hardness and material.

[Muda]

I have two <$10 boxes of every O ring known to man, one SAE and one Metric, for just such a problem.

Jon's going to have to start looking for a new mechanic.

[Richard Pressman]

Jon's going to have to start looking for a new mechanic.

Promises, promises!!

Maybe I'm being too crazy about this but the braking system isn't one where I want to f-up!

See ya next weekend.

[Rob Gibson]

Call Mazda Motorsports. They actually sell a new master cylinder that's not listed on their website. So they should be able to get the o-ring. Also, the '93 model doesn't have an o-ring on their parts diagram. Maybe it was superceded?

[Keith Novak]

Definately bench bleed your MC before installing it. Lots of info out there on how to do it. Essentially you loop some plastic tubing from the goesoutas back to the goesinta and press the plunger with a dowel circulating the fluid until the air bubbles stop. I was suprised how many times I had to press the plunger before the bubbles stopped so it was definately worthwhile.

[Richard Pressman]

Thanks for the info.

I checked the '91 shop manual and the Enthusiasts manual and neither one shows or mentions any type of "O" ring or gasket. I'll still call Mazda Motorsports on Monday.

rjp

[AW33COM]

I may be able to help you next week as I ordered my new Master Brake Cylinder along with every brake part there is (except rotors and rear pistons). Let's see if it comes with the ring.

It is not worthwhile to bench bleed it. You must bench bleed it. There will simply be no brake if you just install it "dry".
Only "flat" master brake cylinders can be bleed on the car.

Thanks for the info.

I checked the '91 shop manual and the Enthusiasts manual and neither one shows or mentions any type of "O" ring or gasket. I'll still call Mazda Motorsports on Monday.

rjp

[Jim Boemler]

What's a "flat" master?

[AW33COM]

What's a "flat" master?

Flat (wrong word selection) MB is a one that sits parallel to the floor. Most MBs sit at the angle.
Those that are installed parallel to the floor can be bleed without removal.

[Richard Pressman]

So if I back the rear wheels up onto a couple of 2x's I should be good to go with a new dry MC -- and a Power Bleeder???

[AW33COM]

^ Good to see you think
In theory it should work, but I have never tired it, and since we will be racing in the same region I'm going to suggest you should do it

On a serious note, if you have your master out you may as well bench bleed it. You do need 2 people in order to install it as one person has to press the brake pedal when you screw the lines in.

[dstevens]

Thanks for the info.

I checked the '91 shop manual and the Enthusiasts manual and neither one shows or mentions any type of "O" ring or gasket. I'll still call Mazda Motorsports on Monday.

rjp

I went out just now and looked at mine as it's off the car and there is no o-ring.

[Richard Pressman]

Thanks!!