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Had an issue with my GSL-SE that I thought I'd share.
Mechanic swapped brake master cylinder, front calipers and pads. After the brake job the pedal was extremely stiff. Mechanic advised that the booster might be bad. Certainly seemed plausible since the old master cylinder was leaking from the rear and could have caused damage to the diaphram in the booster.
Before I went out and spent a bunch of money, I thought I might need to speak with Mike (GSLSEForme). He he suggested we check the vacuum at the booster first, before wasting time and money. As it turns out, the fitting at the intake manifold had carbon and gunk buildup and was almost completely stopped up. That's all it was! Once the fitting was cleaned and reinstalled, the brakes work like a champ! Kudos to Mike - he really is an invaluable resource that is so passionate about keeping these works of art on the road!
While on the subject of brakes - I am probably going to tackle the rebuild of the rear calipers. There is a pretty good video online that shows how.
It may seem counterintuitive-do one at a time. You have the other assembled caliper to reference if you get confused.
Well lit clean area,put old blanket on floor around work area. Something pops free and takes off blanket will trap it instead of it bouncing somewhere out of sight.
Two things to look for on disassembly,pitting thru chrome surface of caliper piston and likewise for piston bore in caliper.
Needle bearings in parking brake section that actuator arm pivots on are sometimes seized as moisture gets in and rusts rollers in cages
Mazda packs the internals to prevent this with a specific grease. I have been able to work bearings with rust penetrant and get them to loosen.
Pitting on chrome surface of piston especially if in area where caliper seal rides makes that piston junk. They are NLA for some time. Same for pitted bore in caliper. This is where it pays to flush your brake fluid biannually.
Pro-tip: that lever arm on a spring which actuates the parking brake function can be removed using a vice to collapse the washer stack and slide the pivot out of the notch in the piston. This will be impossible or will damage the piston if you try to drive it out by force. You must replace the O-rings in the shaft for the parking brake with the orange Vinton rings or it will leak into the boot and onto the ground. Once done, you may never have to worry about it ever again, making it worth doing. When done, pack the entire washer stack and inside the big rubber boot which covers the parking brake mechanism with grease. This will protect the internals from rust.
Can you elaborate on sourcing these orange Viton o-rings? Even McMaster-Carr's selection of chemical resistant Viton o-rings are all black. I don't think color matters though.
Yes! It was because the brake cylinder inside surface obviously gouged on the r caliper. Otherwise the o-rings from rockauto.com worked fine. Replacing the o-rings are easy.
Pro-tip: that lever arm on a spring which actuates the parking brake function can be removed using a vice to collapse the washer stack and slide the pivot out of the notch in the piston. This will be impossible or will damage the piston if you try to drive it out by force. You must replace the O-rings in the shaft for the parking brake with the orange Vinton rings or it will leak into the boot and onto the ground. Once done, you may never have to worry about it ever again, making it worth doing. When done, pack the entire washer stack and inside the big rubber boot which covers the parking brake mechanism with grease. This will protect the internals from rust.
Could you please elaborate on this? I bought the Mazda rebuild kit, assuming it had all the seals/O-rings I need. Is there something else I need to purchase? I will look back at the video so I can see which ones you are talking about.
Last edited by jkmcafee; Jan 8, 2020 at 09:51 PM.
Reason: added pics
The parts Im talking about arent shown on your diagram. Once you get the big rubber boot off, youll be able to see the "wedge" that I'm talking about that is held in place with a big heavy spring and pushes down on a stack of bevel washers below it to provide brake piston pressure through the parking brake mechanism. That wedge is a lever and fulcrum to magnify the force of the parking brake cable tension on the rod which protrudes into the piston cavity to force the piston out. The Viton Oring that I recommend is provided in the kit you have - but isn't Viton, its just rubber. It works fine, but Viton will rarely fail and allow blowby of brake fluid past the washers and into the dust cover boot. It's hard enough to figure a mechanism to remove the wedge and all beneath it, that I made my recommendation to replace the Oring with Viton - a more durable substitute.
Once you get it part, you'll see. It's a simple design, just not very intuitive,
Got the calipers disassembled and it appears I got lucky with the pistons - no rust. Bore had very minor pits but really cleaned up nicely. Local parts store did not have a small cylinder hone so I will have to finish another day. Amazing that the orange "fish egg" colored grease was still in place after 35 years.
Man... this grease looks like it was installed yesterday. Pretty amazing. Looked pretty bad initially... but I got lucky with the piston... no rust... Some pitting in the bore, nothing too serious
May not be pitting, and will likely clean up easily. Be cautious honing these, as every time you do that, you increase the bore slightly. Do it enough and the seals won't anymore - and SE rear calipers are getting hard to find. Better to bleed your brakes more often to ensure you have clean fluid in the calipers and use quality fluid. The rust comes from the hygroscopic brake fluid absorbing water vapor from the air and then that water rusts your everything from the inside. That water vapor content in the brake fluid also lowers the boiling point of your brake fluid which can cause mushy brakes under high heat conditions.
Pack the big rubber boot FULL of grease when you reassemble it, this will ensure no water gets in there and rusts the parking brake mechanism. Also, use the same grease on the bevel washer stack for the same reason. Note the different types of grease which mazda specifies for the piston seals, too. Have at it,
May not be pitting, and will likely clean up easily. Be cautious honing these, as every time you do that, you increase the bore slightly. Do it enough and the seals won't anymore - and SE rear calipers are getting hard to find. Better to bleed your brakes more often to ensure you have clean fluid in the calipers and use quality fluid. The rust comes from the hygroscopic brake fluid absorbing water vapor from the air and then that water rusts your everything from the inside. That water vapor content in the brake fluid also lowers the boiling point of your brake fluid which can cause mushy brakes under high heat conditions.
Pack the big rubber boot FULL of grease when you reassemble it, this will ensure no water gets in there and rusts the parking brake mechanism. Also, use the same grease on the bevel washer stack for the same reason. Note the different types of grease which mazda specifies for the piston seals, too. Have at it,
Interesting... the kit only included petroleum jelly. Would have been nice to have those in the kit. I had seen a reference to the three types of grease (maybe in the FSM) but I don't recall seeing part numbers for the three types of grease. Suggestions?
I use silicone grease for the O-ring on the piston cup, wheel bearing grease for the parking brake assembly under the big rubber boot, and high temperature brake caliper grease for the slider pins, locators clips and a dab on the pad surfaces where they touch the caliper and piston. Mazda FSM states the different greases to prevent low temperature grease from going on the wrong parts and melting which could spread it around the rotor or brake pads. The piston O-ring is obviously sealed by another rubber bushing and typically not a problem if you use a quality grease, as it has the brake fluid as a heat sink to some degree.
The biggest thing is to protect the parking brake mechanism, as the rubber boot will trap any moisture in there and allow it to rust the parts inside,
I use silicone grease for the O-ring on the piston cup, wheel bearing grease for the parking brake assembly under the big rubber boot, and high temperature brake caliper grease for the slider pins, locators clips and a dab on the pad surfaces where they touch the caliper and piston. Mazda FSM states the different greases to prevent low temperature grease from going on the wrong parts and melting which could spread it around the rotor or brake pads. The piston O-ring is obviously sealed by another rubber bushing and typically not a problem if you use a quality grease, as it has the brake fluid as a heat sink to some degree.
The biggest thing is to protect the parking brake mechanism, as the rubber boot will trap any moisture in there and allow it to rust the parts inside,
Thanks for the info. Two things to ask:
1) Would silicone paste be better for the slider pins? Any risk swelling the boots with the brake caliper grease?
2) I have heard that the bearing grease should be put on the washer stack... but there is an o-ring there. Wouldn't silicone grease be best there?
You might be overthinking this; high temperature brake caliper grease is designed for slider pins and will not harm rubber boots. Silicone paste is both high temperature and high viscosity, which may bind on anything which is expecting a grease (vs. paste). The greases I recommended provide a good seal and long life apart from keeping air and moisture out of the mechanisms to prevent rust.
Use whatever you normally use on the slider pins as long as your pads are worn evenly from side to side.
Use whatever you want on the parking brake bevel washer stack, as this is only to prevent rust and water intrusion. The O-ring on the parking brake actuator should either be greased with the same lube you used on the piston O-ring or be Viton for durability. It contains the pressure of the hydraulic fluid, and is where Mazda specifies the special grease be used (*I think it's just silicone grease...).
You might be overthinking this; high temperature brake caliper grease is designed for slider pins and will not harm rubber boots. Silicone paste is both high temperature and high viscosity, which may bind on anything which is expecting a grease (vs. paste). The greases I recommended provide a good seal and long life apart from keeping air and moisture out of the mechanisms to prevent rust.
Use whatever you normally use on the slider pins as long as your pads are worn evenly from side to side.
Use whatever you want on the parking brake bevel washer stack, as this is only to prevent rust and water intrusion. The O-ring on the parking brake actuator should either be greased with the same lube you used on the piston O-ring or be Viton for durability. It contains the pressure of the hydraulic fluid, and is where Mazda specifies the special grease be used (*I think it's just silicone grease...).
Is the high temp brake caliper grease you're talking about petroleum based?
