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my brake booster is toast. I’ve been looking but am not sure what options I have. I would like to get a new one or get mine remand, as I just put a new master cylinder on it. I know there is the 929 and the Subaru legacy booster and master swap. If anyone here has done these, what is fitment like? Do I have to bend new lines or move anything due to length?
That should give you an idea of what the Legacy swap is like. Not a bad job, but like all brake jobs you want to get it right the first time.
Pzr2 had a neat solution with a Toyota MC on the Subaru booster which I think is a bit cleaner. It's more work to find the parts, but you should take a look at his build thread and see if you like it.w
if you want to keep the stock master you're kind of limited to the stock booster, although any mid 80's to early 90's non abs booster Mazda could/should would fit.
different boosters have different levels of assist too, so there is some tuning there, there is a Miata.net thread about it. kind of a rabbit hole.
Mazda kind of has three booster/master combos. everything after about 1978 has the same bolt pattern on the firewall (this seems to maybe be an SAE standard), but the booster to master pattern varies. the 78-85 cars have a vertical bolt pattern, so two bolts up and down. the FC, and every other non abs Mazda until the mid 90's has the same pattern, but the bolts are horizontal, its much easier to work on. the ABS cars have a different mount size between the master and booster, the ABS brake masters are also larger in diameter, which is why we end up swapping these as a unit. there might be something newer, but idk
when you stick with a Mazda master, and apparently Subaru/Nissan the brake fittings are all the same M10x1.0. when you leave this orbit things get random in a hurry, i found a Ford master that is M10 on one port and 5/16" on the other!
pics!
81-85 Master,
FC, pictured is the JDM S5 non abs cylinder, its a mystery to me why they have a different one, as its the same size bore i mean i guess they get the cool JDM reservoir....
ABS Style, this one is a 626, but FC w/ ABS, FD, 929 etc all look like this
In my case it's these options. Find a used one but good condition. Won't hold my breath for that one.
Second option get it rebuild. Found a place that will do it here on the west coast.
third option buy from a mazda dealership. That's a hell no for me.
Im going with the second option and why in particular am I going with this shop. Or will be trying them. Because they are going to let me know if it's doable. So yes I have to send in my brake booster. They will break it down. Assess it. Then let me know if they can do it. So it's a 50/50. A gamble for sure. But very important do to the fact that if successful. I will have a reliable source to rebuild my brake boosters as I'm going to to acquire more fcs down the road.
Another thing careful if choosing the option of a R&R (Rebuild & Return) option with cardone. The cons. Waiting time. Very long turnaround times. I'm talking months and longer. Yeah no thanks
Then there is the problem of your item someone magically disappearing once it's arrives in Cardones hands. And theres a reason for that.
I just did the legacy swap over the weekend on my s5 na because I was tired of the long throw brake pedal. It maybe took an hour. You just need to bend one new line and man handle one of the old lines so you can plug it into a tee. Don't reference the picture in the writeup, use the diagram for reference.
In my case it's these options. Find a used one but good condition. Won't hold my breath for that one.
Second option get it rebuild. Found a place that will do it here on the west coast.
third option buy from a mazda dealership. That's a hell no for me.
Im going with the second option and why in particular am I going with this shop. Or will be trying them. Because they are going to let me know if it's doable. So yes I have to send in my brake booster. They will break it down. Assess it. Then let me know if they can do it. So it's a 50/50. A gamble for sure. But very important do to the fact that if successful. I will have a reliable source to rebuild my brake boosters as I'm going to to acquire more fcs down the road.
Another thing careful if choosing the option of a R&R (Rebuild & Return) option with cardone. The cons. Waiting time. Very long turnaround times. I'm talking months and longer. Yeah no thanks
Then there is the problem of your item someone magically disappearing once it's arrives in Cardones hands. And theres a reason for that.
@Rx7K20 Did you end up sending out a booster to be rebuilt? If so, who did you use and how did it turn out. I have discovered my booster will not hold vacuum. I've been chasing some braking issues and while checking the master cylinder to booster pushrod clearance discovered mine won't hold vacuum. Per the FSM, you are supposed to apply 500mmHg to the booster when checking the clearance, and I can't get it to hold anything.
Anyone have any ideas on these? It looks like first gen ones may have been made by Jido Shakiki Corp under a Bendix license. I've email two different booster rebuilders and neither will touch it or have any info.
Anyone have any ideas on these? It looks like first gen ones may have been made by Jido Shakiki Corp under a Bendix license. I've email two different booster rebuilders and neither will touch it or have any info.
I ended up picking up a different rx7 booster. Found from someone on here. It is still kind of hard to find the other 929 booster or the legacy booster, no scrap yards around me.
I'm pretty confident they are made by JKC with a Bendix license and are of their "Master Vac" variety. I've emailed back a couple of the places that originally said no to see if that helps them. I've also started looking for used ones, but would really prefer the rebuilt route. All of them are 30+ years old at this point. While they may not fail often, they do fail eventually. Would be nice to have new parts in there.
I'm pretty confident they are made by JKC with a Bendix license and are of their "Master Vac" variety. I've emailed back a couple of the places that originally said no to see if that helps them. I've also started looking for used ones, but would really prefer the rebuilt route. All of them are 30+ years old at this point. While they may not fail often, they do fail eventually. Would be nice to have new parts in there.
i think it will end up being JKC. if you look in the shop manual, it actually looks like a really simple device. the hard part looks to be how you would unscrew it without being hit by the spring
and maybe finding a replacement diaphragm.
the NA kit is NLA in from Mazda, and the S5 T2 didn't have a rebuild kit
When I replied back to one place with Master Vac and JKC, it was enough to get them to look harder and they tell me they will have an answer for me on Monday about parts availability. Fingers crossed.
100% strike out from every vendor I emailed. I inquired with five different booster companies and got nowhere on parts or a rebuild service for this thing.
While it looks like a really high quality kit, by definition it isn't. Since this thread is about brake booster options and that kit is explicitly for deleting the booster
Personally I'd love the extra feel about 10% of the time, but the 90% of the time that I drive my car normally on the street, I'd be wishing I had a booster.
With the Subaru booster (or other dual-diaphragm option with larger MC and shorter throw than stock) the feel is already excellent.
While it looks like a really high quality kit, by definition it isn't. Since this thread is about brake booster options and that kit is explicitly for deleting the booster
Personally I'd love the extra feel about 10% of the time, but the 90% of the time that I drive my car normally on the street, I'd be wishing I had a booster.
With the Subaru booster (or other dual-diaphragm option with larger MC and shorter throw than stock) the feel is already excellent.
It is an option, and I know Chase Bays makes high quality stuff - I have their brake lines on my car. However, manual brakes were my last option, and I don't think I am there quite yet. It is a weekend car, but it's majority street driven still.
if you want to keep the stock master you're kind of limited to the stock booster, although any mid 80's to early 90's non abs booster Mazda could/should would fit.
different boosters have different levels of assist too, so there is some tuning there, there is a Miata.net thread about it. kind of a rabbit hole.
Mazda kind of has three booster/master combos. everything after about 1978 has the same bolt pattern on the firewall (this seems to maybe be an SAE standard), but the booster to master pattern varies. the 78-85 cars have a vertical bolt pattern, so two bolts up and down. the FC, and every other non abs Mazda until the mid 90's has the same pattern, but the bolts are horizontal, its much easier to work on. the ABS cars have a different mount size between the master and booster, the ABS brake masters are also larger in diameter, which is why we end up swapping these as a unit. there might be something newer, but idk
Sharing my experience of mixing matching, I did a TII brake swap on my FB using a master cylinder from a 2004 Miata and booster from a 1995 Protege.
The double diaphragm booster provided too much assistance, to get better pedal modulation I choked down the vacuum by sticking another smaller hose inside the booster's vacuum hose.
The cylinders from master to calipers and diaphragms were the same size as the FD's so in theory it should've worked but there's some internal differences.
Just about all the boosters you'll find from parts stores are remanufactured and it's a crapshoot, especially by Cardone.
I originally tried a Miata booster but the reaction disk was probably not installed correctly and it gave a pedal that had no resistance until the end of travel though the brakes were biting throughout.
Another pitfall is the thread going to the brake pedal clevis. Make sure it's long enough and it's the right thread size.
I needed a thread adapter which worked out because the booster's thread was a little short.
02-11-23, 09:12 PM
