Need help! Upgrading to 929 Brake Master Cylider

sep42 · Post by **sep42** » December 17th, 2005, 7:22 pm

Hello,

Need some help. Got a remanufactured 1992 929 brake master cylinder, but the thing just doesn't seal. I didn't realize that the brake fluid container has to be from 929, but that's another story...
The threads are same size, and the holes are in the right places. The part that goes in the brake booster does not seem to seal, and the whole cylinder is raised by about 1-2mm from the brake booster..
The part that comes out of the brake booster is not a problem either...

jschrauwen · Post by **jschrauwen** » December 18th, 2005, 9:25 am

http://www.mx-3.com/phpbb2/viewtopic.ph ... hlight=929

http://www.mx-3.com/phpbb2/viewtopic.ph ... hlight=929

http://www.mx-3.com/phpbb2/viewtopic.ph ... hlight=929

sep42 · Post by **sep42** » December 18th, 2005, 2:21 pm

Well those are the exact same topic that gave me the idea in the first place. I just don't see how it fits. The whole cylinder is raised from the brake booster and the seal is not made at all....

tatsu · Post by **tatsu** » December 19th, 2005, 4:57 pm

On this 323 GTX page they say that they had to replace the booster with one from a 1995 Mazda Protege when using a 1991 929 master cylinder for correct fitment.

Perhaps Luc St. Pierre might be able to shed some light on this, as I know he has swapped in the 929 master cylinder in his MX-3 GS?

lstpier · Post by **lstpier** » December 19th, 2005, 8:08 pm

The 929 MC is *almost* a direct fit. You will also need the 929 fluid tank (early 90s Protege also fits). Sealing is not really an issue - you don't need a tight seal, only protect from the elements, you can fabricate a gasket using 0.125" neoprene or cork material. The most time consuming part is to shim by the proper amount the booster's rod vs MC's cylinder cap (something in the neighbourhood of 0.220"). Shim too much and brakes will drag, shim too little and you'll end up with a big free play in the brake pedal. You need to verify you shiming with a vacuum source connected to the brake booster - see the shop manual for details.

Expect a 14% increased pedal effort from going from 15/16" to 1" of MC bore.

Macen · Post by **Macen** » June 26th, 2006, 8:58 am

Do I need to give the brake booster pressure when changing, or is it just to remove the old MBC and mount the new one? Fill the reservoir with brake fluid and bleed the system and then all should be fine?
According to the OSM I have to apply pressure.
http://www.mx-3.com/95manual/P/P-019.gif
http://www.mx-3.com/95manual/P/P-020.gif

I have to push my pedal more than 50% to get brake pressure, and I hope changing to a "new" MBC will solve my problem.

Steeb · Post by **Steeb** » June 26th, 2006, 1:18 pm

i emailed jeff abrams a couple of weeks back because i was going to make a 929 master cylinder swap thread.
he sent me this link.
http://robrobinette.com/mastercylinder929.htm

after doing some more research on the 929 master cylinder swap, i changed my mind about making the faq because i found that both the 929 and milennia have a 1 inch bore larger master cylinder with the same design as the mx3 v6 master cylinders. i believe the major difference would be that the lines exit on the other side. the lines can be easily fabricated if they in fact exit on the opposite side.

here are some pictures from parts america. i understand that the pictures may not be actual but for most cars, it does show the actual picture for most cars.

this one is the mx3 v6 master cylinder. on the side of the master cylinder it is stamped aith 15/16. if you cannot see it on the picture take a look at the one on your car.

this is the millenia master cylinder. all base, l and s model share the same master cylinder. i dont know about abs cars. where the mx3 master cylinder has the 15/16 stamp, this one has a 1 for 1 inch piston bore.

i was hoping to verify if this swap will work before posting it up but im not planning to do any master cylinder upgrade for at least a few months.

Macen · Post by **Macen** » June 26th, 2006, 3:30 pm

Great link. Thanks!

Here's my 929 MBC:

PATDIESEL · Post by **PATDIESEL** » November 4th, 2006, 11:45 pm

Man I'm in trouble. I have a race in two weeks and my master cylinder decided to die this weekend. (well it might well be the booster too, but I cannot tell without taking them apart. Anyway, I have a 929 MC and wanted to print the direction to install it, but the link is dead to http://robrobinette.com/mastercylinder929.htm. This was the only definative site that I know of that described the install in detail. Anyone have any other sites that go throug the process or has anyone else done it that can shed some more light on the subject other than what Luk has posted.
Thanks in advance,
Patrick

PS, I know I could just get a MX-3 MC, but that would be an even swap when I have the perfect opportunity to upgrade. I swear my MX knows when I need her and breaks so that I'll upgrade something. Spoiled little brat.

atlantamx3 · Post by **atlantamx3** » November 5th, 2006, 12:44 am

http://www.atlantamx3.com/mocaforum/vie ... php?t=2199