Thanks in advance for help with this. I'm four weekends into diagnosing and running out of ideas.

The situation is that I have barely any brakes. The pedal has a lot of travel, very little pressure, and then hits a wall. Dale says it's never the pushrod, and I always believe Dale, but I think it may be the pushrod?

I made a video showing the underside of the brake pedal to give a sense of what I'm experiencing. If you watch the video you'll see that there are four distinct phases of the pedal travel:
1) free play - like what's described in the FSM for pedal adjustment, a few millimeters of completely free wiggle
2) movement without pressure - At the end of (1) free play, the red brake swttch is closed. By the end of this phase the red switch is open, but there is no pressure at all during this phase, even though the lever is moving. It feels as if this phase is the push rod taking up some gap.
3) Pressure - Maybe an inch of travel on the brake. There is definitely pressure, but hardly the stiff pedal I would expect.
4) Wall - The pedal stops moving. At this point I can see the booster and MC flexing in the engine bay. It feels as if the pushrod has bottomed out.

Here's the video:

The pedal doesn't stiffen when pumping (this makes me think I might have gotten a bad MC...but I don't want to believe that...)

Booster is working - if I start the engine the pedal quickly sinks to the floor. Stop the engine, pump it a few times and the pressure returns. With the engine running, phase 1,2,3 basically feel like there's nothing there.

If I drive around, the brakes pretty much do nothing until I get to phase 4 (the wall). If I push all the way then they grab a little, but they don't grab, grab the way brakes are supposed to. (Don't worry, just driving in my driveway.)

Here's the history:
- I had the car in long term storage. Sent it to a mechanic for some work and to get it to pass inspection. He put in new brakes and rotors. We took it up and down the road with turbos going, the brakes seemed fine. Never great, but definitely stopping the car no problem.
- Put the car up on jack stands to work on various issues over the summer. One issue turned into another and next thing you know it's October. Never touched the brakes though. I finally got it all back together and started it up for a test run. Pulled out of the garage and realized there were no brakes. Something had changed.
- No leaks. Calipers are moving, so I figure it must be the master cylinder. It must have been on the verge and just finally went bad while sitting, or maybe I blew a valve pulling out of the garage.
- No problem - I was eager to mod anyway - so I replaced the flex lines with Sakebomb lines, replaced the MC with a chips motorsports 929, replaced leaking ABS unit with a non-leaking (and presumably working) unit, installed Russell speed bleeders. Bench bled the MC, and bled the brakes. Took it off jack stands with total confidence. Ugh, no difference. The brakes won't grab.
- Let the bleeding begin... "Bench bled" the MC again (while installed, with short hoses - much easier than actually bench bleeding). Yeah, some more air came out. That must have been it, right? Bled the brakes with my Motive power bleeder. Confidently took the car off the jack stands. Dammit, same problem.
- Read every forum post on bleeding. Okay, so I gotta "jolt" the air out since the whole system was open. Time for old school bleeding. Got my son to press the pedal for an hour. Some air came out, yup. Took her off the jack stands again. Dammit, same problem.
- One more time the old fashioned way. This time there's no air coming out, just fluid. This time I didn't bother bringing it off the jack stands - I'm paying more attention and can tell the pedal hasn't changed.
- Okay, some forum posts say it took them all day to bleed the car, so I put the Motive power bleeder back on and loaded it up with a full quart of fluid. I started by bleeding at the front passenger wheel with the theory that there might be air in the ABS. I let a full pint of fluid work its way through but didn't get a single air bubble. For good measure I re-bled all the brakes in the proper order, letting gratuitous amounts of fluid come through. Not a single air bubble. Turned on the ignition and bled them all again. No air bubbles.
- Calipers still press and hold. No leaks (very small amount of weep at a MC banjo bolt). I measured the pedal height and travel according to FSM and it seems to be within spec.

So that's where I'm at, now wondering whether the push rod might have somehow come out of adjustment. Seems like such a long shot. Why would a push rod go out of adjustment while sitting on jack stands? Or, maybe I got a second bad MC? This has been known to happen. I guess I'm going to have to take the MC out and test on the bench by plugging the brake fittings (these MCs are real hard to fit into a vice for bench bleeding though!). This is where I'm heading - taking the MC off, checking the push rod, testing the MC and then going through the bleeding process all over again...

...but am I missing something?

 

If no leaks and circuits hooked up correctly, internal bypass seems the most likely situation. Larger MC here (not chips or OEM) needed pushrod shortening......the female MC pushrod receptacle was machined slightly differently.

 

^That statement concerns me, there should be zero evidence of leaks or weeping anywhere in a brake's hydraulic system. If it's showing signs of weeping at a MC banjo bolt, it means its leaking and fluid & air can get in or out from that site. Fix that issue and bleed the system again before doing anything else.

 

so once you've got that leak fixed, the pedal end is really easy to check, and its probably pretty close to being right.


the other thing that may need to be checked is the clearance between the booster and the master, its fiddly to measure it, but it makes a huge difference if its not right
Mazda has a little special tool, and one side you don't need it, but the other you kind of do, so you need to be a little creative (if you had a 3d printer it would be easy to make one)



with mine, going from 0.030" of clearance to closer to 0 made a big difference.

 

Thanks for all the input. Good point on the weep. I've been avoiding it because it's hard to get right but I need to address it.

For pushrod adjustment, a prior thread mentioned that the Baer Brakes Master Cylinder Pushrod Length Gauge would work but that's just for measurement. Is the Mazda SST necessary to make the actual adjustment? (I find those FSM drawings impossible to interpret).

(P.S. I checked the pedal position according to FSM and it's within spec).

 

nope, its just hard to measure. Mazda's tool looks like it bolts in place of the master and booster and then has a threaded thing to get the clearance

 

The symptoms you described point to a leak in the hydraulic system or a bad master. Since you have done the master and mentioned dampness at a banjo bolt and since you had everything apart, a leak in the hydraulic system is the most likely culprit.

The pedal throw / adjustment rod will not cause the symptoms you describe.

Pressurize the brake system and look for leaks. Easiest way that I have found to pressurize the brake system is to take a piece of wood or jack handle and place one end on the brake pedal and wedge the other end against the seat to activate the brake pedal. Then wait (overnight, a few days), feel and watch for dampness at every connection from the master down to the bleeder screws.

Good luck.

 

You guys were right about the hydraulic leak.

I used Gracer7-rx7's technique to put continuous pressure on the system. Couldn't find a piece of wood that fit but a long-*** carpenter's clamp did nicely.


I diidn't need to wait a day. The leaks were immediately apparent. Both banjo bolts were leaking under pressure (not just the one that had evidence of weeping).



There was also fluid seeping out from the bottom of both coupler connections. It was pretty easy to find leaks by running my finger with a latex glove up each brake line. I did the old mechanic's trick of loosening and tightening 3 times which did seem to dry things up. This is almost impossible with the inside fitting because of the angles but I managed with a bit of manhandling.



So now I'm left with the question of how to get the banjo bolts to stop leaking. I used new copper washers but I had a hard time finding the right size. I think I ended up with an outside washer that was 1.5mm and the inside that is 1mm which I think was the OEM width. I tightened to 30ftlb which I think is about as tight as I would risk on the banjo bolt. I think I remember someone else reporting trouble with the OEM banjo bolts on the 929 MC and they ended up getting different ones from a brake shop. Any words of advice on this?

Maybe I should just bring the MC to a brake shop and have them fix up new fittings and lines. I think in an ideal world you could get the MC on a bench and test the entire contraption for leaks before installing in the car but I haven't found a way to get it snug in a vice.

 

Answering my own question with a Youtube dive on sealing banjo bolts: make sure surfaces are smooth and clean, get the actual OEM crush washers, they're a standard ford part 99562-1000. This was a helpful video:

You Tube

Seemingly cheap crush washers are sometimes not soft enough. When I took the original crushers off they had a pretty deep groove from being pressed up good and tight. I tried annealing them but the groove never puffed out. I ended up melting a washer so gave up and got new ones, but I should have been more patient and ordered the OEM.

 

There are aluminum crush washers that are usually much softer than the copper ones. They are intended for use on brake or fuel banjo fittings. I've successfully used ones from both these sources.
https://www.mcmaster.com/products/cr...+crush+washers
https://www.pegasusautoracing.com/pr...p?Product=3278

 

Another tip is to not over-tighten those banjo bolts; there is a spec in the FSM for this, and I'm pretty sure it's significantly less than the 30 lb-ft mentioned a few posts up. Another tip is to ensure all mating surfaces are clean & fee of any debris/grit and lubed with a bit of brake fluid. And always use new crush washers - in the same size and quality/material as the OEM ones.

 

Glad it helped.
On my Miata, I had similar problems with seapage from threads on the bleeder screws of the calipers. The calipers are all so old at this point that many of the remans have had the threads stretch and wear. I had to resort to using thread sealant (not thread locker) on the bleeder screws to seal them properly. I imagine that the same thing could have happened at those hydraulic fittings. Or perhaps it's just the crush washers as others mentioned.

Anyway, this is what I used to seal the threads and stop the seapage: https://store-speedbleeder-com.3dcar...lant_p_19.html

I briefly tried to look for a comparable, generic product from Permatex but couldn't easily identify the correct sealant that is rated for hydraulic fluid like brake fluid so I just got the stuff from Speed Bleeder. Maybe someone more knowledgeable than I can inform the community what the equivalent generic product would be. This stuff has been reliably working in my Spec Miata for a few seasons now. YMMV

 

@Pete_89T2
Any tips on how to practically execute on that? Most torque wrenches require a socket - which won't work on some of the areas where he (and I) had leaks. Also, your typical torque wrench will not fit in the areas where some of these fasteners need to be torqued.

I've tried in the past to use the torque wrench as I tend to overtighten everything. Can do on calipers. Impossible to use in other areas - at least for my inexperienced self.

 

Would a "crows-foot" open end 3/8" drive wrench work? You're not talking about needing a lot of torque. The crows-foot wrench will change the torque a bit from what the wrench reads because the lever arm may be longer depending on the crows-foot orientation.

 

I couldn't find the torque spec for the MC banjo bolts in the FSM. I might be blind. I originally set them at 17 ftlbs because that's what the brake line banjo bolts take, but when it continued seeping I pushed it up to 30 because that's what the ABS banjo bolts take. Didn't matter in the end because it seeped at 17 and it seeped at 30.

FWIW, I bought a 1/4" torque wrench and it's been very handy. It fits in small spaces and it's good for all those bolts that are spec'd for low torque ratings. I think it goes up to 22 ftlbs.

I think the ideal would be to get the MC completely set-up while it's outside the car and easier to access. The main problem I had with that approach was getting it to fit snug in my vice, but maybe it's just too small.

 

I just went though a similar situation with my car that had been sitting up awhile. Even with a little seepage, you should still have some pressure I would think. I found one of Dale's older threads about rebuilding the master cylinder and saw where another member was discussing the internal bypass and pulled my master completely apart. I found all the seals to be in good shape but my bypass was stuck, the spring for the bypass valve is very light so they apparently stick after sitting a long time. Its worth a shot to check yours, its fairly easy to do. After I reassembled mine with a good cleaning and making sure the valve would close reliably, I bench bleed it and upon reinstalling it I had instant pressure. good luck

 

A crows foot open end on the appropriate drive torque wrench would indeed work just fine for situations like brake lines where you can't get a socket on it. And yes, it will add a small error to the torque reading, but the % error is small enough that you can usually ignore it. Another option for fasteners that you can get a socket on, but can't get a normal torque wrench to work due to accessibility issues would be a digital torque measurement adapter - something like this: https://www.harborfreight.com/38-in-...SABEgJFI_D_BwE Of course there are higher cost & better quality/accuracy products on the market, but it was easy to find a cheapo Harbor Freight item to link to

Here's what I could find in the '93 FSM regarding torque specs on the various master cylinder line fittings & fasteners...

 

I'm not crazy right, there's no torque spec for the banjo bolt itself, right?

I ended up ordering both copper and aluminum washers from pegasus because that's what it took to get over the minimum $5 order. Their 3/8" spec matched OEM perfectly for ID,OD and thickness. I noticed the note on the Atkins site for the OEMs that said "copper or aluminum depending on what Mazda sends us", which I guess means either will work. The pegasus site specifically highlights that the copper ones are "soft copper" so I'll probably try those first. OEM would have cost me $29 for four washers ($3.25 per washer + shipping). As ready as I was to just pull the "go oem" lever, that seemed egregious, so I'll TOFTT.

Crossing my fingers that this is the end of the odyssey. Will report back after this weekend. Hopefully this thread helps someone else in the future.

 

Yesterday I took the MC out to install the new washers and re-set all the intermediary fittings. While it was out I figured I'd go ahead and measure my pushrod. I ordered a cheap ($14) tool from Amazon. The main issue I found was that our master cylinders are much longer than standard MCs so I had to use the tool in reverse.

In this first photo I'm setting the tool based on the depth of the MC bore.


The measurement out of the other side now is about 9 mm.



Here's the part of this process that's ambiguous so maybe others who have been in here can help. Inside the booster, the pushrod itself has a few mm of forward/backward play. You can grab it with two fingers and move it back and forth. I guess the first question is whether this forward/backward play is normal? I think this play roughly equates to the "phase 2" of pedal travel that I described in my original post, so if this play is normal then presumably the excess pedal travel might also be normal when bleeding with the engine off.

The FSM says to attach the SST and then apply vacuum. Well, we can't apply vacuum with this tool since the booster is open so presumably the SST actually seals the booster? The question is then what vacuum does to the pushrod. I have to presume that vacuum would stiffen up the bladder and probably pull it forward, otherwise there's be no point in applying vacuum during the procedure.

In this photo you can see how our pushrods are hidden inside the brake booster like a frightened turtle. It'll be challenging to adjust the length. Looks like you'd need to get two needlenose pliers in there or something, get creative like j9fds3 mentioned.



So, if I manually pull the pushrod fully forward then the measurement is pretty much perfect. As Dale says in the lore, "these almost never need adjusting", this seemingly perfect measurement does add another bit of evidence to the theory that manually pulling the pushrod forward for measurement is the correct approach. The FSM doesn't give an actual tolerance spec, but other sites and videos seem to indicate .5 to 1 mm tolerance to be typical (no video I've seen however shows a booster that has a pushrod that has play).



While I was snapping photos I thought I'd also show off how I adapted an RX8 vacuum check valve. This is another one of those stupidly expensive parts, and it's not clear whether any-old check value will actually work. This one came off ebay for $12 with hoses which just needed a little careful trimming. Downside is that it's more effort to get on and off than the OEM assembly (which has a bullet check valve inserted as a pill) and adds a few more sharp edges when changing oil filters.

(You might also notice the Jaz catch can sitting below the booster. There's one photo somewhere on the site where Dale has a picture and I copied it. Fits in this spot nicely if you fab a little aluminum L bracket to hang off that inside bolt.)

 

on the FC the booster isn't open, and you can apply vacuum. i guess its possible that on the FD style the master actually seals it, although that seems weird

 

On the NA Miata, the rod length is adjusted at the pedal pivot point under the dashboard. The FD might be similar. The rod is a bit sloppy on the Miata too but doesn’t seem to make a difference in pedal feel or brake application.

 

different rod! there are two, pedal to booster, and booster to master (or primary bedroom or whatever)

 

Today I bench bled the MC (on the car, much easier) and used gracer7-rx7's technique to pressurize the MC. The new copper washers from Pegasus stopped the leaks at the banjo bolts (FWIW, I also sanded the sides of the banjos with 400 grit in a circular motion until they looked perfectly flat and cleaned them with brake cleaner). One of the brake fittings still weeped after install (the inside one of course) but a twist/untwist/twist got it to stop leaking.

Bled at the calipers again. Well... I'll find out later because it's raining now. Plus, I finally got my hands on fender liners which I'm going to install before I muddy up my wiring harnesses again (any tips on where to source the anchors and/or little 8mm bolts is welcome...).

But I'm not optimistic. The pedal still feels pretty light with the engine running, though I need to get the wheels on the ground to be sure.

Meanwhile, I'm leaving it pressurized overnight to check for any slow leaks.

 

So, is this video accurate? If fluid is coming out of both lines when you bench bleed then the MC is fine? Or is there more to it, such as things going wrong inside the MC when it's actually fully connected and under pressure?

 

When I went through this the master would move fluid fine just not build any pressure. I really would investigate the bypass valve inside the master, its not too bad a job. good luck