midnight mechanic

In 1990, I purchased a clutch master cylinder from the dealer. It leaked all over. Therefore dealerships suck. I can provide more examples.

Fast forward to now, the brake master cylinder needs to be changed. It is 14 years old and the brake pedal goes 1/2 way to the floor.

I don't want to try a rebuild kit, because I've had an unsuccessful experience.

Question is, for something that varies in price from $20 to $170 what are everyone else's experiences good and bad?

Removing /installing/bleeding/adjusting brakes are a real PIA.

ps...I figure the rear slave cylinders are due for a change too.

DreamInRotary

iTrader: (49)

I have had bad experiences as well. With the master clutch cylinder and slave clutch cylinder - both had issues.

What is the trim model of the car you are looking at? GSL and GSL-SE are most expensive compared to the S and GS trims.

I'm a fan of replacing with new and skipping rebuilding, after my experiences with the clutch stuff. But I've also made the rebuilds work.

RockAuto is the best place to look for them, cheapest as well.

midnight mechanic

it's a GS.

I could buy the rebuild kit, the boring thing, and develop the skill set, but master cylinders last about 14 years.

I ordered from O'Reilly's. Wanted to do NAPA, but O'Reilly's said they'll have it in two days. Both have similar part numbers, so I think it is the same manufacturer.

And none of the local car parts places have the front disc caliper springs. Doesn't matter, because I'm a one project at a time kind of mechanic. I feel like a gremlin

DreamInRotary

iTrader: (49)

O'R and Napa probably get their parts from the same place, as you said

I'd look on RockAuto for those front disc caliper springs, they have just about everything you'd need for the car. They come highly recommended by me and other rotary owners on the forum here as well.

Hope it all works out for you!

Kaaarl12a

iTrader: (6)

Got my anti rattle springs from rock auto.

gerald m

Your story is pretty common , failure most often occurs due to lack of understanding and tools to do a proper job on cylinders weather master or wheels. The cyls. need to be cleaned and fine honed to a smooth finish and assembled proper , Some kits suck and should never be sold , Some kits are for more than one application and often the parts for one cyl. are used on the wrong one .
Usually hydraulic brake parts are priced reasonable and is a better move to buy new rather than rebuild . Myself I like to rebuild if possible ( Far to many parts thrown away when there is nothing wrong with them )sometimes they need to be new but I also enjoy the job as some just want to change and go . I have even heard of people rebuilding the master and slave cyl. and using ample amounts of engine oil to lubricate for ease of reassembly which turns the brake cups to a soft swollen mass of blubber. .. Always use brake fluid and nothing else to lubricate parts for assembly and always bench bleed the master if possible before installing on the vehicle , it will save you a lot of pump screwing around . Most often on older applications with shoes (Not in your case )on the rear if the brake pedal needs to be pumped once or twice the shoes need to be adjusted rather than brake work . More often than not rear adjusters are stuck and do not work so as the shoes wear they need to travel farther to make contact with the drums. Good Brakes save lives and are relatively cheap to keep in good repair . Sometimes old rubber brake lines get weak and swell enough under pressure to make the brakes feel soft . . Have a good one . Gerald m.

rx7lives

When I did my brakes and clutch hydraulics, I used all new parts I got from Kragen. I think the master cylinder was around $50 new and the clutch master was cheaper. I think the calipers were around $50 a piece as well. The quality was good all around.

I highly recommend that even if you get a new clutch slave cylinder, you also buy a cheap rebuild kit. Its saved me on the road more than once. One time the slave piston was ground down at around a 45° angle. Looking at how the geometry between the slave and the clutch fork is, it's no surprise 1st gens eat clutch slave cylinders.

midnight mechanic

Ok, I changed the master brake cylinder, but first I bled all the old brake fluid. Did the one man bleeding thing. The new brakes were hard, and barily worked.

This web site pointed to vacuum brake booster system as the culprit. Trouble shooted the system with a vacuum pump. And you were correct. Thankyou. The hose clamps solved the problem.

Question: is it too much of a coincidence that both the master brake master cylinder and a vacuum hose would go bad? Would a bad vacuum brake booster mask a bad spongy brake master cylinder? The original problem was spongy weak braking.

gerald m

Possible that the hose was made loose when working on the master ? that would be my guess .. Have you road tested to make sure the problem is gone .

midnight mechanic

no but yes
the hose in question was on the passenger's side so I couldn't have knocked it loose.
road test showed that the brakes are great!

now I replaced the two rear wheel cylinders, and the brakes suck again!! paint on the internals( brake shoes , wheel cylinder, springs, adjuster) is all peeling and it is all cruddy, and the inside of the wheel rims is cruddy so I hope that it is the wheel cylinder that was leaking. And not the wheel bearing.

also the c clip that holds the adjuster was "gone". parking brake sucks too!!

what gets me is why did mazda engineers put the adjuster on the same side of the axle as the wheel cylinder?

I hate drum brakes!!

rx7lives

Did you use Silicone brake fluid? You should use it on the brakes and the clutch hydraulics but you must completely flush the system or you won't get silicone's advantages.

The advantages:
It is not hygroscopic unlike ordinary brake fluid. This means that it doesn't absorb water so you don't get the rusty looking inside of the hydraulics that destroys the rubber seals so your moving parts last longer without any water in the system. I also think that silicone has a higher boiling point which doesn't mean much on the street but it helps with brake fade if you do 'spirited' driving or track days.

The disadvantages:
It costs more.
If you have to refill, you have to use silicone but this shouldn't be a problem since you should carry a bottle around for emergencies or the inevitable loss of the clutch slave cylinder. You can use regular brake fluid in an emergency but you will then lose silicone's advantages until you flush the system again.
I've heard and read that it is supposed to be harder to bleed. I've used it for almost thirty years and whether you bleed using a friend to push the peddle or a pressure bleeder or my favorite (and cheap) the Mityvac it seems to be just as easy as normal fluid although it is a bit thicker.

Oh yeah, as your car is old, your rubber brake lines are probably not in the greatest shape but Mazdatrix sells a complete stainless set for around $100. You can feel the difference in the pedal although it might just be that my rubber lines were so far gone. You can also get an SS line for the clutch as well for around $18.
Brake lines: DOT Stainless Steel Brake Lines
Clutch line: Cart Price Check Part:6508

Mazdatrix isn't the only one selling these, in fact, I might have bought mine from Racing Beat but they fit perfectly and you get the relief of not worrying about a burst brake hose. I had it happen to me once when a friend was giving directions and he told me to turn too late and when I slammed on the brakes, the left rear line burst. Not a comforting feeling but it was at night with no one around and it still stopped and I was able to limp home easily.

Good luck.

gerald m

Don't know if dot 4 brake fluid is like silicone fluid or not but FYI dot 4 brake fluid does not destroy paint and is used in most motorcycle applications for that reason I believe it has the same characteristics as silicone but not sure .. ..

Your getting there . maybe next time you do brake work if you do it all at once then you will be only frustrated one time .. Really brakes weather drum or disc are usually a very simple procedure it just takes some learning and understanding on how things work . get some penetrating fluid on the emerg. brake adjuster so it don't get twisted off .. If the paint is peeled at the rear it is unlikely that it is gear oil as it shouldn't remove paint like normal brake fluid . RX7lives is right when it comes to brakes always use good quality products . When in doubt just ask , someone will help . Gerald m.

Careful with that emerg. cable or that will be the next thing to replace.

rx7lives

I forgot about the paint, a very welcome side effect! You're right about the paint peeling on the backing plate being from brake fluid I think as well as soaking the adjusters and all moving parts in penetrating oil. There's nothing so fun as a stuck adjuster since if they're seized, the automatic adjusting feature won't work as well as not being able to back off the shoes if the drum has a large lip and won't come off. I've on more than one occasion had to pry the drums off which destroyed the two clips that hold the brake shoes to the backing plate, fun.

It is a good idea to check the play on the axle, listen to how they sound when they turn for any rumble or grinding which could mean a bad wheel bearing as well as looking for gear oil seepage. If the axle seals leak, not only do you lose the lubrication in the 3rd member but you ruin the brake job you just did.

It's also very important to get the link that moves the adjuster automatically so you know it can turn the adjuster. It's been a while since I've done drums but the adjusters might also have opposite threads so one loosens counter clockwise while the other is clockwise and if they get mixed up, the automatic adjusters will loosen the brakes instead of tightening them. Mark all parts when you remove them, check to see if the adjusters are working in opposite directions and verify everything with the FSM as well as taking a picture of them once the drums come off. Just make sure you know which picture is left or right.

If the shoe's braking material is different lengths, the longer one goes towards the rear but I would double check with the FSM as it affects the self energizing type drum brakes.

On the drums themselves, check for evidence of metal to metal contact. Also check to see how big the lip is on the side of the contact surface that goes inwards. If it's too big it can make it a nightmare to remove them and if it is out of spec, they need to be turned but I would check the price of new ones as it might not be much difference and if the drums are too far out, no one will turn them.

The problem with rebuilding wheel cylinders is that you don't know how many times it has been done or honed so you should use a caliper to see if it's in spec.

It really doesn't cost much more to buy new parts rather than rebuilding old parts with an unknown provenance and you get peace of mind as well.

If you don't have one, get at least enough flare wrenches to fit all the hardline nuts where it goes into the cylinder. If you crush or strip the nut, you will have a bad day. There's also a tool that helps put the springs on but pliers or vice grips work as well in my experience and having a tool that does just one job is not usually worth it unless you do it daily or you need to get the pilot bearing out of the eccentric shaft. That tool is well worth the $100 just for one use!
If you don't have one, a Mityvac is a good investment for $15. It makes bleeding a breeze and a one man operation.

If the costs start to really add up in the rears, you might want to consider going with disks if you can find a good donor car for parts that you can't buy at Kragen like the disk style backing plate or the emergency brake cable and hardware. I don't know if you need to worry about the proportioning valve or that check ball in the master cylinder but if you have a donor car, grab them as well.

I've found that the hardest part about drums is the stuck parts and the lung cancer inducing dust even though they don't use asbestos anymore. Finally, it takes less than five minutes to change the brake pads in disks while drums take a lot longer if you have seized parts.

Good luck, get it right and pat yourself on the back.

midnight mechanic

rx7lives, so you have resurrected many a rusted up junkers. Only thing you left out is when all else fails , heat things up with a propane torch. The threads on the adjuster spanner are different driver/passenger side.

Never had luck with the Mityvac technique. The pump the brakes, hold the pedal down with a board, and open and close the bleeder valve is my strategy.

Vise grips , pliers, screw driver, c-clamp , and a 24 inch dia hose clamp is the way to go. The thing with a hook, on large pliers was useless. The hook gets in the way of getting the large spring in the hole.

I think automatic adjusters are not worth the trouble. I have two washers on the auto adjuster, maybe I will put two more? But it is really time to change the 30 year old drums.

But riddle me this: why did the mazda engineers put the adjuster be on the same side of the axle as the wheel cylinder?


ps....what I should do is have "budget brakes" , "Mieniki", or "brakes 4 less" give me a "free estimate".....their quote of $1000's of dollars is always good for a laugh. And watching the liars have an aneurism when they loose my business is "priceless"

The parking brake cable housing looks like the next thing to go.

rx7lives

Ah, it gives me shudders when I realize the drum is rusted to the axle shaft. Not fun but at least on the 12A 1st gens, it doesn't have studs and my experience when a drum is actually rusted to the shaft, it's the hole in the drum that goes over the axle. Penetrating oil will help but I would say I've had a less than 50% luck with oil alone and I'm not even talking about drums that don't come off because of a large lip. 1st gens use thinner metal on the drum compared to a land yacht like a '69 Pimpala so you can do a little or a lot of pounding and it will come off.

My problem with a torch is like the kid with a hammer, soon everything needs to be heated to get things loose... They do work though but if you've already saturated the rusted area with oil, you get a nice fire so it's worth having a good, maintained fire extinguisher.

Now that you mention it, I can't picture the drums from a 1st gen in my mind's eye like I can a Chevy. Does the Mazda drums have a floating pin on the bottom or is it fixed. Does it have a square screw that sticks out pointing towards the car to adjust the shoes?

Does anyone have a picture from ether side of the mechanism once the drum is removed and of course I can't find my manual nor a pic in the FSM so I can verify what I've written.

rx7lives

I've never had any problem with automatic adjusters as long as they're lubed up and setup correctly but to be honest, I don't really know if they ever really did anything.

I agree about that funky tool they sell to help hook up the brake springs, it actually seems harder to use the tool than simply vice grips or pliers.

Mityvac's work great but if you don't use the little reservoir to hold the fluid, the fluid goes into the vacuum pump part wreaking havoc. Keep them clean and they work forever. The method where you have an assistant is a good one as well as long as they follow your directions to the letter. Years ago, I used my mom to do it and it worked fine.

This reminds me why I dislike drums so much!

midnight mechanic

[QUOTE=rx7lives;11306781]Ah, it gives me shudders when I realize the drum is rusted to the axle shaft.

Now that you mention it, I can't picture the drums from a 1st gen in my mind's eye like I can a Chevy. Does the Mazda drums have a floating pin on the bottom or is it fixed. Does it have a square screw that sticks out pointing towards the car to adjust the shoes?

my fb gs 1983 has a spring connecting the bottom of the two shoes. No square screw. To adjust the brakes, there is a spanner with a saw tooth nut that the auto adjuster is supposed the rachet. It helps to coat the saw tooth nut with silver anti seaze so you can find it with the drum back on while adjusting it.

I wonder if I should get new drums? The drums are 7 15/16's ID, and I have two washers on the spanners. Might as well get them while I can. RockAuto shows some brands are discontinued/final close out.....but I finally got the brakes right, "if it isn't broke, don't fix it"