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As part of replacing the failed brake booster on my 72, I chose to suction most of the fluid from, and remove the master cylinder from my brake lines. Didn't want to risk bending brake tubing. After the new booster is in place, is it necessary to bench bleed the master, or can I just install it and bleed the lines as normal? I'm only asking because if I should bench bleed, I need to secure some plugs to block the line connections. Thanks

Today, I started on what I hoped would be the straightforward job of rebuilding the brake master cylinder for my 70 Z. Disassemble, clean, install new seals and hardware, and reassemble. Job done. What could go wrong? Unfortunately, I only got to Step 2. After cleaning things out, I found a little divot in the floor of the cylinder bore, located about 1/2" aft of the rear stopper bolt. Hard to say what cause it. The car has been sitting for many years so I guess it corrosion damage. It's about 1/8" in diameter and deep enough to catch my fingernail on. The rest of the bore is in great shape. When I look at the cross-sectional view of the Brake MC in the 71 FSM, I see that this divot sits pretty much mid-way between the front and rear seals of the rear piston. Knowing that, it doesn't seem like the seals stand a chance of being nicked by it. Nor do the rear piston and seals that came out of the cylinder look like they've been hurt by it. So - Question 1: Can I get away with just leaving it as-is? If the answer is that it's going to be ok to ignore it, then I've still got a minor problem in that that the rebuild kit that I bought a number of years ago is not suitable for the 70 - 71 brake MC -- different seal types (even though the bore is the same). That leads to... Question2: Anybody know where I can get a rebuild kit for the 70-71 MC? If the answer to Question 1 is 'MC must be replaced', then I've got a much bigger problem. The 72 MC, while an improved design, has the front and rear reservoirs and lines flipped around -- which means that my hard lines won't fit. Plus, a 72 MC would dilute the 70-ness of the car's engine compartment (a small but touchy consideration). MSA lists the early-design Brake MC as NLA. The typical parts suppliers also show 'NLA'. Then there's Rock Auto... Rock Auto shows NLA for 70, but lists two units for 71. One is from Cardone, the other from Centric. When I look at their 72 listings, there are about 6 choices, including Cardone and Centric. The 71 and 72 Centric units have the same PN, so that one's undoubtedly the 72 design. The 71 and 72 listings for the Cardone units, however, show different PN's. In addition (although this may mean nothing), the pop-up picture of the 71 Cardone unit shows the 70-71 design, with the 'F' line/reservoir at the front and the 'R' reservoir/line at the rear. Question 3: Does anyone have any experience with the Cardone unit listed under '1971' from Rock Auto? Could it possibly be the real deal? (i.e. the 70-71 design). If these 70-71 brake MC's truly are NLA from anywhere, what do members recommend as a remedy. Am I really going to have to fit new hard lines? or... Question 4: If I am forced to fit a later-style 72 MC, does anyone know if I can install the internals from my 70 MC into a 72 casting , thereby keeping the reservoirs/lines in the correct, 70-71 orientation? Both castings have a 7/8" bore and -- other the placement of the stamped 'F' and 'R' markings -- I think they may be identical. Intuition suggests that the factory would have made efforts to keep the same casting when they upgraded the design, limiting the changes to the internals (and the hard lines).

Hello All, I have decided to upgrade the front brakes in my 11/70 240z. I ordered cross drilled/slotted rotors and the 4 piston caliper kit from MSA and before I install them I have a few questions. With the new calipers will I need to upgrade the brake master cylinder? What about the brake booster? If anyone has any experience with this, I'd greatly appreciate the input! I'm also leaving the stock drums on the rear! Chris

I recently posted in my reliability update the my brake booster was leaking. Once it gets bad, its easy to diagnose: A sucking sound in the cabin when brakes are applied along with hard braking and engine surge during braking. Long story short: All of this goes away once the brake booster is replaced and everything is properly re-attached. Early Warning Signs What I didn't realize is that my Z was telling me for a few weeks that the brake booster was going bad. It did this with an occasional engine surge at idle (it would only go down to maybe 1500 rpm's at a stop light). When this happened though, I would give the throttle a quick kick and it would get back to normal. Because of this behavior I attributed the problem to my recently adjusted dashpot (prior to adjustment it was out of the picture) or a sticky linkage. I figured it was getting sticky and it was on my list of things to look at some day. During this period when the brake booster was going bad, there were no other braking problems. Braking was strong and there was not cabin noise while braking. Fast forward to about 10 days ago and I get the classic brake booster issues: Hard braking, sucking sound in the cabin during braking, engine surge during braking. So I replace the brake booster (see cautionary tale below) and the brakes work really nicely, classic symptoms are gone. But, now, also gone is my stop light slight engine surge. No more need to kick the throttle (yay!). A Cautionary Tale Some of you may have caught this on the Help Me board. I change the brake booster last week. Its really an easy job to do (maybe 2 hours, if that - you do have to be a little bit of a contortionist to get to the bolts under the dash). Don't make the mistake I did: It turns out that the replacement booster was somewhat larger than the old one (and I can feel the difference in braking). When I went to hook up the master cylinder to the hard lines I was careless in alignment (I think maybe that the larger booster slightly changes the alignment of the hard lines to the master cylinder slightly) and I could not get the hard lines connected. In the end, I wasted more than a few hours recovering from this and I almost had to replace one of the hard lines but managed to dremel out the burr that I had created while thrashing with the lines. So, be sure to always get those brake lines nicely square before attempting to connect them. If you search the Help Me forum for finger blisters, you can find the whole story. Here it is all done though (I decided to paint the new booster, I think it looks good):

Hello All, First off i am new to my Z, and new to the forum. Im sure my problem has been discussed previously but i am having some very odd symptoms! I bought my car maybe 2 months ago. After sitting 30 years in dry storage the whole brake system was shot. I purchased all new pads and shoes and retainers and rebuilt the calipers and the wheel cylinders, along with new flex lines. I also bought the correct master cylinder for my car, it being built in 12/1970. My problem is that even after bleeding the entire system, i cannot get pressure to the front calipers. The bleeder on the master to the rear has pressure, but the front bleeder, once opened, does not. The pedal pumps up and seems rock hard. Please I have no idea why i am not getting pressure to the front system. Oh and the reaction disk is glued to the back of the pushrod so that did not fall out of place.

I am slowly rebuilding a 1973 240z. I was getting leaking from a rear cylinder and a front caliper was not getting any fluid so I replaced both rear cylinders, new brake shoes, new front calipers and pads, and a new master cylinder. I bled the master cylinder first and then bled all four brakes beginning with the right rear using a vacuum bleeder as well as the traditional buddy system. I have checked over all the lines for leaks and have found nothing. No matter what I do I can not get a good solid brake without pumping them a couple of times. When I depress the brake pedal my brake light comes on. According to the manual this could indicate a pressure differential between my front and rear brakes. I can get my rear brakes to lock up but my front brakes always feel like they are barely working. Does anyone have an idea of what the problem could be? At this point about the only thing I have not replaced is the master vac, the NP valve and the warning light switch. I am very frustrated at this point as I have moved a lot of brake fluid through the system, replaced a lot of parts, bought a fancy vacuum bleeder that I am not impressed with and still don't have good brakes. I have taken the time to read many, many posts here. I have found some excellent advice but nothing that matches this problem. I am rebuilding this with my son for him to drive and I won't let him move it until I am positive he has great brakes. Any help would be greatly appreciated.

1970 240Z Front brakes are good no air in the system (toyota 4piston). Back: Nissan Maxima disk. Had to rebuild driver side rear due to leak. Went to bleed get no pressure to both rear calipers and not much flow. When cracking the rear bleeder, the brake pedel does not go to the floor it stays the same. When Bleeding the front it does go to the floor. Got some people helping me out and this is what we think might be going on. 1. porportioning valve locked out the rear when it was leeking. I have opened the electrical part on the top to get a look at the valve. Not sure what way it should be, at this point the small diameter part is at the firewall and the larger is just in view at the front. 2. Front part of the master cyl not working (1980 280zx master) on the 280zx it is opposite the original 1970 master cyl. So the front feeds the rear brakes. Tryed to bleed the front to push the valve back in place. Did't work. Could have hydralic lock working against the rear keeping the fluid locked out of the rear. I don't have the diagram of the distribution valve to see how the lock out part works. All my books in storage. At this point I only have front brakes. Anybody run into this before? Need some help/suggestions.

I went through my brakes, put on new rotors and pads, new back brakes, wheel clylinders, stainless braided lines, cleaned out the old nasty fluid from all the lines and put in DOT 5 fluid. what happens now is that the brakes will function great, good pedal for a indeterminate amount of times and then they will go to the floor and the brake warning light comes on! Sometimes it will be one good pedal and maybe the next time it will be 6 times and they always pump up fine. I'm stumped!