Where to buy a 929 Master Cylinder

[Rhino]

Had a bit of spongy bake pedal earlier today, while I'm fairly sure that it probably just needs bleeding, I'm tempted to replace the master cylinder seals due to how old they will be. The Mazda master cylinder seals seem to be about £90, I'm wondering if its worth upgrading to the 929 master cylinder if its not much more?

Does anyone have any recommendations on where to buy one, as the eBay links in the a previous post on here seem to be dead, as the items are no longer available on eBay?

I'm running the standard brake setup with Carbone Lorraine pad, and Motul RBF600 fluid.

Thanks

 

[Nas80]

Its not an upgrade. Its bigger so it just makes pedal effort harder.

 

[GAVBEY]

I have one for sale if you want? £60 delivered?

 

[JoeLanger]

Yeah only really required for big brake kits,

I rebuilt y master cylinder, piss easy job, more difficult to bleed, but I paid a man for that!

 

[Ceylon]

If you don't have braided lines, getting some will help with the spongy pedal.

 

[Rhino]

The brakes had been fine, it was only after a bit of heavy use the pedal went slowly go to the floor. I pulled over but there were no leaks on any of the calipers or under the car, plus the reservoir was still full, it was only after a couple of hours and pumping the brake pedal repeatably that it got some pressure back up.

I'm 90% sure that its air in the system, but the brake master cylinder is original so could also be the cause.

As a minimum I think I should change the brake master cylinder seals, but it looks like the cost difference between seal kit and a 929 master cylinder isn't that much and I'm expecting to go to a big brake kit sometime in the future. Plus I sorta prefer a harder brake pedal with less travel.

I've re-built all the calipers, have brand new stainless hoses and have remade some of the hardlines in cunifer. The only things on the brake system I haven't touched are the master cylinder, servo, ABS unit and proportioning valve. I checked for fluid in the servo vacuum line as well.

 

[Nas80]

That sounds definitely like the seals in the master have worn

 

[Spendyrx]

Yeah as nas says! Seals go inside the master....shows no leaks but defo seals gone! Happened to me!
Also get that 929 servo from gav! Bargain price there

 

[4packet]

Did you use the Bigg Red rear caliper kit? I tried 2 sets of seals and they would only last 1 trackday before they started leaking. Hard to spot until you remove the dust boot. I think the air was drawn in after the brakes were applied. I could left foot tap down the straight to get the brakes working again, but if I forgot, the pedal would nearly hit the floor and would get barely 70% braking force. Ran though the gravel at Silverstone GP once as a result. I have fitted Budweg ever since. They seem slightly larger in diameter and have not had an issue since. Possibly not as severe as your issue, but I already had the 929MC fitted and the Stoptech pistons are smaller, so masks the issue slightly.

With my brake setup the 929MC feels great, I even spent some time looking into the Subaru 1” option. When I fitted Stoptech pads (instead of Carbotech XP10’s) for an Alpine tour, I was surprised how heavy the brakes felt though. Not sure how the friction levels compare with CL pads.

 

[4packet]

Oh and from memory I looked up the part number on Rockauto, then found it slightly cheaper on eBay searching by PN. There are a few different companies producing them with and without reservoir and some are refurbs.

 

[Rhino]

I have used the Big Red rebuild kits so I'll check under each dust seal for signs of a leak. I've only done about 300 miles in the car since I've got it back on the road and nothing hard on it like a track day.

I had seen the ones on rockauto but they're different manufacturers or re-manufactured, and on eBay only Atkins rotary had an OEM one. I was wondering if anyone else had a different source.

I've contacted Gavbey regarding the one he has though.

Its a bit frustrating as I've got it booked in for an alignment next Tuesday.

 

[4packet]

Worth checking all the connection for leaks. The smallest of leaks can really mess up the pedal once the air gets in. Which hoses did you use? I sacked off the HEL ones as the sealing design looked suspect to me. It butts up end on, rather than on a taper. Fitted Goodridge in the end.

Regarding the OEM MC, I'm not sure what you gain from OEM parts after a good few years out of production. Once the original stock has dried up, the parts are typically sourced elsewhere. It's not feasible to maintain the original production facility for a few service parts, so the part generally changes. Even if the part comes packaged up from the original supplier, they have possibly outsourced the manufacture/assembly. Not saying it's true in this case, but likely. I chose one of the reputable makes with new reservoir and not remanufactured (an expensive one) and it's been fine. It was only about £115 landed from memory.

 

[Rhino]

Hopefully over the weekend I'll get some time to get the car on axle stands and go over the entire braking system. I didn't see any signs on leaks at any of the hose connections when I was checking for leaks in the calipers. I used Earls for the brakes lines.

I did find this, there seems to be a valve inside the MC that can cause a similar issue, which I wasn't aware of:
https://www.rx7club.com/3rd-generat...ster-cylinder-how-i-spent-my-weekend-1124717/

I'm going to be getting the 929 MC off Gavbey