# 1987 RX7 brake issues [Resolved]



## rj13b (Apr 5, 2007)

hey guys,i have a 87 RX7 GXL and my front brakes keep locking up when im driveing. its weird, i can be driveng normal,ya know cruising,having fun and all of a sudden, my front brakes start locking up and once it slows me down to a dead stop (or something else causes me to stop) my front brakes lock up completly. if i wait about 20 minutes or so the brakes release and it drives normal again,can't figure out the problem and can't affored $80 just for a diagnoses. i've replaced the brake booster and the master brake cylender,i checked the brake lines for cloggege,i thought maybe my abs computer was going out so i disconected it (it its not hooked up,i shouldn't have abs,right) but the problem still remains. the car drives normal for about,i don't know 5 miles or so,then the front brakes start locking up. please help me,all thoughts would be appreciated,i'll try anything at this point. 

thanx in advance
RJ


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## qldit (Mar 26, 2007)

*Re: 1987 RX7 brake issues*

Good Morning rji3b, that problem is symptomatic of the master cylinder piston not returning fully past the fluid return port.
This kind of thing somtimes happens when a booster is replaced and the distance of the thrust rod is not set correctly or the pedal is not coming back properly. 

Check the pedal return is correct and if no success you will have to check the manual for the correct rod adjustment procedure at either the booster or from the booster to the master cylinder.

If these are not set correctly the brake fluid pressure cannot return to the master cylinder and causes this exact problem.
It may also be some restriction in the master cylinder not allowing the piston to return to it's end.

edit. When you fit the master cylinder there should be no spring pressure applied to the the master cylinder as the rod from the it booster locates.
In some machines there was adjustment under the dash to adjust the pedal rod length, but most now have a different adjustment idea on the rod itself.

Once you know about this you won't get caught again.

The rear brakes will also be affected but not as much as the fronts, it is deceiving.

Cheers, qldit.


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## rj13b (Apr 5, 2007)

*Re: 1987 RX7 brake issues*

thanx alot,bro. i'll try ur idea in the morning (sux though,i'll have to rebleed the brakes). but if neither of those are the problem,u have any other idea's? thanx...RJ.


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## qldit (Mar 26, 2007)

*Re: 1987 RX7 brake issues*

Good Morning again rj13b, I would be pretty sure that will be your problem, rebleeding is a nuisance but a neccessity.

Before you get too involved check your brake pedal is fully returning, you might have a broken spring or something silly like that.

Is there any possibility the pedal rod might not have located in the socket in the back end of the master cylinder piston?

It used to be a common type of problem where the brake pedal pressure was not present until the pedal was well depressed, so someone would adjust the rod length without realising the importance of the piston return.

Best of luck old chap!

Cheers, qldit.


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## rj13b (Apr 5, 2007)

*Re: 1987 RX7 brake issues*

thanx,i'll deffinatly check the pedal return first,in fact i'll do it just shortly,then if a broken spring or something is the problem,i'll know what to go and buy in the morning. thanx again.....RJ


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## rj13b (Apr 5, 2007)

*Re: 1987 RX7 brake issues*

ok. i checked for pedal return and its fine. i've been trying to figure out how to check the booster piston and set it,but i have come to a conclusion that i have no idea how to do that,i can't figure out how to adjust it. can someone explain it to me? also,i drove the car for about a week and a half or so before the front brakes started locking up,if it was booster piston not adjusted correctly,wouldn't the problem have started sooner? i have had a few ppl lately to tell me i need new front brake calipers,but then i had ppl say that if it was the calipers then the brakes would stay locked up instead of coming and going like it does. i can drive the car for about 5-6 miles or so then the front brakes lock up,then i gotta let the car sit for about 30mins and by then the brakes are free,after that i can drive the car as long as i need to,as long as i don't shut the engine off,if i shut it off then im back to square one again.could it be happening do to a bindage in the pads? or maybe the pads need to be replaced,could having a almost bald brake pads cause the problem? please give me any advice u can,thanx.


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## qldit (Mar 26, 2007)

*Re: 1987 RX7 brake issues*

Good Morning rj13b, yes it may well be caused by the brake pads being worn, there is only one piston in the caliper and its outward movement is doubled by the distance of the worn pads. Normally the pads would have three eighths of an inch meat on them, so if they are both worn on each side the caliper piston moves considerably more distance and may in remote cases be sticking.
I have never seen it happen personally but have heard of that possibility.

There is normally a restrictor in the fluid return circuit to the master cylinder to ensure the pads remain in very close proximity to brake disk as they wear.

The braking efficiency drops off markedly when the pads wear down to one eighth of an inch thickness, I always reccomend never letting them wear that much.

When they do wear really thin the wear rate increases and is liable to damage the brake disk.
Also the brake disks actually wear and can exceed wear limits and reduce braking effect and also amplify this kind of problem because the pad wear and the disk wear is excessive cumulatively.

Normally when you remove the wheel and expose the caliper you can undo one of the caliper retaining bolts and the assembly will swing away to allow the pads to be removed.
Some vehicles can be more complicated.

Because the new pads are much thicker, the caliper piston then needs to be compressed fully otherwise when the new pads go in there is insufficient room to allow the caliper to return to its operating position.
I usually use a normal "G" clamp to do this, but remember there is a lot of fluid in those caliper cylinders and when it is pushed back up into the master cylinder it will cause it to overflow, the preferable alternate is to release the brake bleeding nipple at that caliper so that excess fluid is simply lost at that point as the piston is carefully fully compressed.

Ensure any anti-squeal shims are fitted properly when they are present and the brake pads are correctly located in their slots.

As I say, I haven't seen that problem personally, and in that it is on both wheels it seems very odd. 

In the manual there is usually a measuring distance for the master cylinder thrust rod from the booster face at rest, but as a rule of thumb that pushrod should not move the master cylinder piston as it is fitted and properly located. You can nomally feel this as you push the master cylinder into its locating position on the booster before securing it. 
In some models that rod length actually adjusts at that place simply by turning it one way or another, but I am not sure with your machine.

You can get a fair idea of how it looks by measuring the insertion depth into the master cylinder piston rear-end then to the master cylinder rear body length then deducting and distance to the MC mounting flange face, then measuring the distance that the rod protrudes from the Booster face. and comparing the two.

Remember that there is a significant multiplication and mechanical advantage of surface area with the MC piston as against the caliper cylinder surface areas so there will also be a "travel distance" increase at the master cylinder by ratio, so it is quite important that the insertion depth of that pushrod is pretty accurate. 

It is common for persons to increase that rod length to try to "crib" a bit of extra pedal performance often when other errors are present elsewhere in the system.

This often causes the problem you described where the fluid is unable to return to the MC because the return port is blocked by the piston being too far forward.

However your mention of this problem clearing after a period then operating notmally would possibly indicate the temperature of your calipers when cold (due to closer clearances with the pistons) may be involved with your problem, following that theory would support the caliper pistons sticking for some reason, especially when the pads are significantly worn and the caliper pistons are well into their limits of travel.
Having this happen on both wheels is mystifying. 

Sorry can't get much clearer with this.

Cheers, qldit.


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## rj13b (Apr 5, 2007)

*Re: 1987 RX7 brake issues*

i had the car for over a year before i ever got insurence on it. i bought the brake booster about 4 months before insurence and bought the master cylender the same day as i got insurence (wich was feb 23rd). i had replaced the rear calipers cause the seals were blown before the booster went out. when i replaced the rear calipers i also replaced the rear brakes. then i checked the front brake pads and they still had half life so i didn't worry about them. i thought had replaced my front calipers (maybe i was dreaming or something) but i was looking through my receipts and realized that i hadn't replaced them. after i bought the new booster,i went to bleed the brakes (back right,back left,front right,front left) when i got to the front left,the master cylender went out.....then i lost my job the next day....the master cylender costed $85 and when i found a new job i wasn't getting enough hours to buy it on 1 check (really bad hours,didn't keep the job for long) so i was trying to save for master cylender but by the time i got paid again,something came up and i had to spend the $ i had saved. so when my income tax came in,i bought the master cylender,got my insurence and started driving the car,then i was having problems in the cooling system,the car kept running hot,i replaced everything in the cooling system (starting with the thermostat) and after everything was new,i found out i had a bought a bad thermostat. (i was told at that point that the only thermostats that worked for the rotarys were through mazda) i talked to a friend and he said get one through napa....so i did and it worked. i drove the car for another 2 days and the brake problem started,no,wait scratch that,it started everytime the car ran hot,but i was told by a few different rotary specialists that is was normal for weird things like that to happen when the motor ran hot,they said that whn the motor ran hot,it would cut the power to most of the other electrical itams such as the abs causing the front brakes to lock up.then after i fixed the cooling problem it stoped happening for 2 days,then it started again but now the cars not running hot,so not sure if its connected or anything. but before i got into that,i was saying that i had half life on my front pads and once i had brakes i only drove the car for about a week and a half. weird thought though,when i do drive the car,my brakes react differently depending on how quikly i press on them,like if i press the brakes slowly,then the pedal goes down to the floor before i the car stops,but on the other hand,if i press the brakes quikly,then the pedal only goes down halfway before the car stops,i was told that was normal on the RX7's but it just doesn't sound right. also,sometimes if i press the brakes slowly when the pedal almost get to the floor,im not slow enough to where i feel like i will stop when the pedal does reach the floor,so then i quikly press the pedal to the floor and im stopped right before the gets to the floor....weird,eh? not sure if any of that helps or not but i thought it seemed important to say. oh,also, the piston needle thingly on my brake booster is kinda lose (just doesn't seem tight enough) and it won't screw in or anything,i bought it from advance auto parts (where i buy everything if i can) and they said it was supposed to be that lose feeling.still doesn't seem right,but its their part so they should know. my brother mentioned adjusting it by where the pedal connects to the booster,he said i have 3 different settings and i should try putting it on the one that was the furthest away from the floor,but thats where it already was,so still not sure how to do it. i don't know,sorry the post is so long but i thought it all might help in figureing out the problem. please any ideas and i'll recheck my front brakes pads in the morning........RJ


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## qldit (Mar 26, 2007)

*Re: 1987 RX7 brake issues*

Good Morning rj13b, that is interesting, firstly that pedal travel with lighter pedal pressure is generally symptomatic of a faulty master cylinder if the system is properly bled, fluid leaks back past the piston seal.
What actually happens is the the MC seal flexes harder against the cylinder wall when the pedal is more rapidly applied and that bypass leakage doesn't happen as much.
I would be very careful with that problem, it is most noticeable when driving in slow moving heavy traffic.

I always test using low pedal pressure checking for that exact problem.

I usually get stainless steel sleeves fitted to master cylinders, it helps avoid a lot of odd problems.

Yes, thermosts can cause a lot of problems, I like to sit them in a pan of water on the stove slowly raisng the temperature and observe their operation, but some have a bypass in them to allow slight water flow past the wax element in them to allow it to react by allowing hot water through, otherwise they don't work in the car, so it is very important to get the correct part. 

Radiator fluid anti-corrosives can also gel and cause blockage problems, but that is normally in the bottom of the radiator and can restrict or block the water path. VW Golfs were pronne to this. 
The radiator fluid types should never be mixed and need to be drained and replaced periodically to avoid these kinds of problems.
Some cooling systems need to be bled to get air out and avoid "air embolisms" in the system when they are refilled.

I haven't struck an ABS system where the front brakes wouldn't release but itis entirely possible and could easily relate to you problem.

I can't explain how an overheated engine system could have effect.

So far as I know the ABS only releases pressure to the brakes, but it is entirely possible that module has some problem that is causing this effect.

Do you have a Mazda repair organisation where you might ask their techs, here they usually have a time in the mornings for speaking with technical specialists. 
Those ABS systems can be quite complicated and contain moving parts that could "hang up".

When I strike nuisance problems I replace the all the brake pads and ensure the MC is properly fitted and then properly bleed the system as you describe before I try to troubleshoot further.
There are no shortcuts with this hi-tech stuff, everything needs to be set properly.

I think you may need the manual on that machine with a procedure for troubleshooting that ABS system.

I suspect you may have more than one problem.

I would be careful driving it until you find the actual problem, I would suggest not driving it at all really, it could be very expensive and dangerous for you.

Cheers, qldit.


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## rj13b (Apr 5, 2007)

*Re: 1987 RX7 brake issues*

first off ive come to the conclusion that it is infact the master brake cylinder. Ill be going in the morning to order a new one. I havent driven the car out of my neighborhood since the brake started to act up. thanks very much u have been a big help and if u think of any other ideas plz just post them up! appreciate it. 
.....................RJ


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## qldit (Mar 26, 2007)

*Re: 1987 RX7 brake issues*

Good Morning rj13b, I usually dismantle the master cylinders and if there is no cylinder wall damage just replace all the seals.
It only needs a pair of circlip pliers to remove the circlip and the piston is then easily removed.
Most aluminium types have anodised internal cylinder walls, so if you might do this don't use any abrasive material if you clean the internals, if there is any pitting, (usually along the bottom) scrap the master cylinder and simply replace it.

I like the stainless steel inserts, I have access to a repair organisation that does that and they give better service than the original and cost a bit less than a new MC.

Cheers, qldit.


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## rj13b (Apr 5, 2007)

*Re: 1987 RX7 brake issues*

the mc was defective,i took it back and explained to them what was going on and they said it was deffinitly the mc. the new one will be in on tuesday so i'll have it fixed then. they said that if that doesn't fix the problem then they would send me somewhere to have it diagnosed for free (no money out of my pocket) lol. but i'll deffinitly keep u posted on what the comes out after i put the new mc on.i tried everything u had posted for me before,and then after nothing worked out for me,i took the mc off and took it back to the part store yesterday and ordered the new one. its great that i had trouble shooted it already cause they asked me a billion questions and after everything came out clear they defected it out. so i'll be getting a nice shiny brand new one again,lol. then the car will be sold hopefuly by the weekend and i'll be something else,most likely a nissan 240SX.....maybe if i have any problems with it,u can help then too,lol.anyways thanx alot............RJ


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## qldit (Mar 26, 2007)

*Re: 1987 RX7 brake issues*

G'day rj13, that sounds like a decent organisation, I will be interested to hear how you go. 
Well done,
Cheers, qldit.

BTW, I like Nissans, I have 2, one a Patrol and one a 2.6 Litre sedan.
They are beautifully engineered machines.


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## rj13b (Apr 5, 2007)

*Re: 1987 RX7 brake issues*

hey dude,i wanted to let u know that i replaced the master brake cylender and the brakes work just fine now,no more problems  thanx for everything!
RJ


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