240Z Brake Questions

[timhypo]

So, let me start off by saying I have a fair amount of brake experience for someone who's never worked on cars professionally - I adapted a later dual-channel master to my wife's '58 Olds including building my own pedal with the correct 6:1 ratio, fabricating the plate to change the mount position, building the actuating rod, etc. In the course of doing this, I did a LOT of brake bleeding.

I'm now trying to fix my '72 240z. Over my tenure owning this car, the brakes have ALWAYS been the problem. In fact, the previous owner told me that they were his biggest problem and he was tired of messing with them. He did a bunch of hokey stuff, including bolting the rear wheel cylinders to the backing plates - inadvertantly defeating the self-adjustment. When I got the car, it had been sitting forever and everything was rusted together. I knew a guy who had just done a bunch of mods to his 240z front brakes for autocross and he GAVE me his stock calipers/discs, which worked fine. I swapped them in, replacing the wheel bearings, and adding braided lines. I replaced one rear wheel cylinder that was beyond repair and unbolted the p/o's jackassery with the other wheel cylinder. I also replaced MOST of the hard lines as they were rusty to the point of breaking off when I'd remove one. I've also never been able to get the brakes right.

This weekend, I replaced the master, thinking that must be the root of my problems. I still cannot, for the life of me, get a firm pedal. I've bled the master, both wheel cylinders, and both calipers. I've run three BIG bottles of brake fluid through the thing. I get a semi-firm pedal, but way too squishy for my tasts. Do early Z cars get a firm pedal like every other car when they're right? What am I missing? The service manual I got online has ZERO about bleeding brakes. I hate shotgunning parts at a problem, but I've put up with it here because it's brakes and old cars should have new brakes. Does anyone sell plugs that go in brake components? My thinking is that if I plugged the rear-outlet at the master, bled the front, and got my firm pedal - I'd have started to isolate the problem - or vice versa. This is getting pretty frustrating and Cincinnati's way to hilly to even think about rolling on even remotely questionable brakes...

[S30Driver]

Did you follow the correct bleed order for the brakes, driver rear, pass rear, pass front, driver front? Sounds like you know what you are doing with the brake system.

Are you confident the master was bench bled properly?

Pedal should be firm especially with the stainless flex lines.

Over on zcar.com , do a search on fart method , a solid way to bleed the master, might be some help to you.

Another possibility is the new master is bad, wrong one. I know there was a change in 72 vs the early master, ports were reversed.

[Bonzi Lon]

I agree with the 'fart method'. After sitting 26+ years and several attempts to get them bleed, the 'fart method' worked, rather messy, so be prepared.

Bonzi Lon

[timhypo]

Did you follow the correct bleed order for the brakes, driver rear, pass rear, pass front, driver front? Sounds like you know what you are doing with the brake system.

Are you confident the master was bench bled properly?

Pedal should be firm especially with the stainless flex lines.

Over on zcar.com , do a search on fart method , a solid way to bleed the master, might be some help to you.

Another possibility is the new master is bad, wrong one. I know there was a change in 72 vs the early master, ports were reversed.

I'm NOT confident I got the right master. The one in my Haynes notes that the 240z master has the front-brake reservoir in front and that the 260z master has the rear-brake reservoir in front specifically. The master I got had the front-brake reservoir in the front, as did my car. I chalked it up to Haynes being notoriously inaccurate and/or the P/O being a jackass. Rockauto only lists one part number for all '72 240z's and they're usually pretty accurate, correctly noting the pre-7/72 rear wheel cylinder.

Shouldn't I start with the passenger-side rear? It seems like it's further away from the master.

I'll look up the 'fart' method on ZCAR.com...

[timhypo]

I also read an excellent write-up on v8-240z.com regarding this and he specifically leaves the front master bleeder open with the hose in the front reservoir while bleeding the rears to avoid fighting the front brakes in the process and avoid fighting the proportioning valve. Obviously, I'll reverse the process for the fronts. I'm gonna try that tonight. Most of my brake experience is on all-drum cars, so it makes sense that I've never had to mess with the proportioning valve.

[Zed Head]

I had a very similar problem with my 76 280. I just got off the O'Reillys Auto site and see that they use the same caliper so you might have the same issue.

The previous owner of my car did some brake work on the car and accidentally put the calipers on the opposite side that they came off of. This put the bleed valve at the low end of the caliper instead of the top, creating a huge bubble that was impossible to bleed out. Once we figured it out, and swapped them back, it just took a couple of pumps to bleed the fronts.

The big clue was that there was a large amount of fluid from the reservoir going somewhere when the pedal was pushed, then coming back when the pedal was released. It was taking up the volume of the bubble as it compressed it, then pushing it back when the pedal was released.

Also, with the big bubble, the front brakes could be pumped up with several pedal strokes.

[timhypo]

My bleed valves are definitely at the top of the caliper.

[doradox]

There is a not very common thing that happens that can cause your problem. If you have a misalignment of the rotor and the caliper it will cause a spongy pedal. The rotor face and the caliper piston faces should be parallel. But say if a front spindle is slightly bent then your rotor face would not be parallel to the piston face. The caliper piston has to travel a little extra distance to make up for the misalignment and causes extra pedal travel. It is not at all common so I would certainly exhaust all other causes first though.

Steve

[Walter Moore]

I also had done a lot of amateur brake work by the time I first started trying to get my car drivable. I fought with the brakes for over a year until I finally gave up and replaced EVERYTHING with OEM parts. Now the brakes work fine. But I have a constant nagging fear that eventually I will have to replace something, and the whole process will start over again.

[dclamm]

quote: "The master I got had the front-brake reservoir in the front, as did my car"

Timhypo, I believe early 240's (70-mid 71) had the front reservoir (larger one) towards the front of the car. But my understanding, that changed by '72, the front reservoir was towards the rear of the car. The early MCs are much more rare (and much more pricey to buy).

[timhypo]

That's what my Clymer says as well. Unfortunately, what I have is what's available and, since mine's 7/8 just like the original, it shouldn't matter. It might though, and if I continue to have issues, I'll look into finding an original, but they might be just as bad as mine. I managed to get a hard pedal last year with an identical master that came with the car, but it went away after a few days. I still think I have something wrong in the system. The plan for tonight is to get my wife to help me bleed them again, with the opposite master's bleed valve open and feeding into it's own reservoir and, if that doesn't work, I'll replace the remainder of the hard lines on the assumption I have a leak somewhere I don't know about. If that doesn't work, I'll replace the final wheel cylinder. If that doesn't work, I'll roll it down the hill and set it on fire.

In other news, I ordered a Unisyn and the Z Therapy 240z TuneUp video today...

[timhypo]

Doh, misread. You're saying that my 12/71-built '72 should have the reservoir in the rear. Makes sense.