Captain Obvious

Yeah baby!!! A free Z!! I think I'm good on bumper trim, but I could use a steering column to mess with. And a power brake booster to scavenge for parts to put together one good one. Oh, and inner tie rod ends that I can screw around with too... I want to try to cut open a pair like @EuroDat did.

That's what I was suspecting. It comes down to expectations... You had none, so the hard pedal was "normal". I would fix the system up as soon as you can afford though. And after what I've seen with the rebuilt units, I'd be comfortable running a used booster as long as it has never inhaled brake fluid from a failed master cylinder. As Patcon mentioned above, that's probably the most common cause of a failed booster. pffffft... Never driven anything older than 97. I've not yet owned anything NEWER than 99. Ever!! Even my kids car is seven years newer than mine. Man... I gotta get out more.

Awesome! Just remember that now you're driving around with rock hard brakes. They work, but could be a problem in a panic situation, I got my rebuilt booster from Rock Auto, and I didn't check stock, but I would be surprised if the one I got was their last one. I would assume they have more. But if I were going through it again, I think I would pay a little extra at a brick-n-mortar local store for the ability to open the box and see the booster before I paid for it. Out of curiosity... You bought the car and it came to you with the booster blocked off with that bolt, right? Didn't the brakes feel a little firm to you? Or since you had never driven one before, you thought they were supposed to feel like that?

I'm no marine biologist, but I've heard they use this process undersea with the help of sharks.

Me too. I promise I won't tell you mine if you promise not to tell me yours. Not counting either of us, of course!

Naaa. No disappointment. I understand completely. My time married is less than yours, but it's a lesson that doesn't take thirty-five years to learn.

Me and my first Z. Picture of a picture of a time long gone: I should show this to my kids to prove that despite what they think, I really was cool at one time

Haha! Well don't be too sure I got it right! These cars have a way of teaching you a lesson. You'll know more after you disconnect the brake booster and plug that line. Hopefully you'll get your smooth idle back.

OK spill it... What happened?

Here's some info I put together a while ago about the water temp switch: Interesting that, as Zedhead suggested, the documentation indicates the location of that switch to be at the passengers feet in 73. In 74 they supposedly moved it to the thermostat housing, but prior to that time, it's supposed to be inside the interior. Appears that the documentation is wrong. Also, none of that helps you find one, but thought you might like the read.

The red arrow points to the control signal line for the evap system. It should also be tied into the distributor vacuum line. It could be the source of a small vacuum leak. The green arrow points to the vacuum supply line for the power brake booster, and it could be the source of a much larger vacuum leak. If your car runs fine with that brake booster line plugged but won't idle with that line connected, then your brake booster is probably leaking internally and needs attention. You also mentioned that you hear a vacuum leak when you first shut off the engine? I suspect your brake booster is toast.

I built a wooden "fixture" and with enough danger and mechanical advantage, I got my old booster open. Yes, it involved danger, and yes it involved a BF dead blow hammer. And a face shield. Unfortunately, I have not yet found the smoking gun as to why it wasn't working. The symptom was that it held vacuum (even with the engine off), but did not provide any boost. Seems like it would be a problem with the poppet valve, but I can't find anything wrong with it. Current theory is that it is clogged with deteriorated foam debris of what used to be a filter. Tomorrow I will try to figure out a clever way to test the valve in operation without putting the whole booster back together.

Cool. Good luck. Actually, my suggestion would be to put the car back to where it was when it ran good and then take some pics for us. Then we can discuss emissions changes from that point?

Well you have just reaffirmed my reason behind why I have not attempted that maneuver. Good luck... We're all counting on you!

I wouldn’t be ready to condemn the BCDD quite yet, and I am confused by a couple things in your original post... First thing is that there is only one externally visible connection to the BCDD, and that is an electrical one. There are a couple vacuum connections made to the BCDD, but none of them are externally visible. They are all made internally to the throttle body and are not visible without peering into the throat of the throttle body. So when you say "the BCDD was disconnected and lines running to and away from it were blocked off", if you're talking about some vacuum lines being capped... Those vacuum lines originate from the throttle body, but despite how close in proximity they are to the BCDD, neither of them have anything to do with it. One of those vacuum lines should be connected to your distributor and carbon canister, and the other vacuum line is used for the EGR system. So if you're having troubles after messing with those vacuum lines, it's not the BCDD's problem. If you are talking about the electrical connection to the BCDD, that connection is a kind of "dead man switch" such that when that wire supplies power to the BCDD, the BCDD is deactivated and should have no impact. But if that wire was disconnected, your BCDD was active at all times. Second thing is about you hearing a vacuum leak after you turn the car off... As soon as the engine stops turning, the manifold vacuum goes away, and there are two places where that vacuum is "stored" while the engine isn't running. Those two places are in the HVAC system, and in the power brake booster. Both of those systems should have a check valve in series with them to prevent that vacuum from bleeding off, but I'd start looking there.

Cool. Thanks for the check. And props to you in that you certainly seem to have a great handle on the tracking and recovery part. Paired with some deterrent and prevention, it would provide formidable coverage. The deterrent thing, however, can be a double edged sword. You can't plaster "Protected by Geosky" stickers all over the car because part of the tracking and recovery process includes some secrecy. Even if it is a respected system amongst thieves, it is certainly easier to defeat if it's not a surprise. In fact, there was some mention of jamming devices earlier in this thread... I didn't look into the existence, but being an EE, I can attest to the plausibility. If someone is casing the car and knows it has a cell or satellite based transponder in it, it just makes it easier to disable. Big dogs, a siren, a huge chain to an immovable object, a fuel and/or ignition disable, AND your device. They would have to really really want that car. Other ideas? Stink bombs. Iron Maiden played at volume 11. Taser built into the driver's seat. Remotely activated, of course. That "YOU HAVE TWENTY SECONDS TO COMPLY" thing from Robocop...

I got my training in how to use one of those U-Haul trailers from Jim at Memphis 2015. After that, I put that training into practice fetching a derelict project car for my son. Nose first. The built in harness wheel straps do a great job of holding the front end, and I don't think you really need additional straps in the rear, although they certainly can't hurt. If I were hauling something worth as much as Jim's car, I might feel compelled to use straps in the rear. I, however, was fetching something worth much much less. And I was towing with a rented U-Haul truck as well. Their truck. Their trailer. I followed their instructions. Something goes wrong? Their problem. Mostly.

Fuel pump prime would be a perfect application for a momentary switch. But this is a 73, right?

I just took a quick look at my booster, and the input shaft is actually closer to the bottom than the top. Had the direction of the offset wrong. Doesn't really matter since the clamshell can be assembled in many different positions, but I did edit and fix that above.

Woof. And I thought mine was ugly. How can they sell that with a straight face???

I didn't consider the 81ZX booster as I didn't see much of an advantage replacing one difficult to find booster with another difficult to find similar priced booster. The real trick, as Zedhead suggested, is to find a booster with the same firewall bolt pattern and the rest can probably be made to work. That's what I spent a little time on, but didn't turn up anything. I don't even think it needs to be the same diameter. The stock booster on my 280 was the 8 1/2 inch version and I think an inch or two smaller would be fine. I might actually even prefer it. An inch or two larger (as evidenced by the ZX booster "upgrades") works as well. Just a softer pedal I assume. I'm pretty much positive that there is a good alternative out there, but finding it without dimensioned drawings from the manufacturers is hunt and peck. I'd be happy to be part of the team that does the investigative work into an alternative and so far, the asymmetric input shaft compared to the mounting holes has been a non-starter for me.

rc240z, Don't get me wrong... I wasn't poo-pooing your product in any way, nor was I talking to you specifically. I was talking about systems in general. But you're right about "resistance" being relative is exactly why I used the phrase "theft resistance" instead of "theft proof". I do not believe there exists a system that is theft PROOF. The trick, however, is to make the car deterrent enough that does not become a target and resistant enough that it at least not is a successful target. And if all else fails, make it recoverable. I think the perfect system goes something like this: Make it deterrent enough that most threats are dismissed before they start. Make it resistant enough that most threats which were not deterred are at least thwarted without success. Make it trackable and recoverable such that threats which ARE successful can hopefully be reversed. Some additional details that I think are important would be: The deterrents should be non-ugly, non-intrusive, and low on the false alarm scale. The resistance measures should attempt to minimize damage done to the vehicle as part of the theft process. The tracking should be very surreptitious and difficult to defeat. Haha! You can send my consulting fee checks for high level system design.

I'm no expert in the field, but I think the best system would employ theft deterrence, theft resistance, AND aid in recovery in the event that the deterrents and resistance didn't work. Stickers and a flashing LED from Harbor Freight might provide a little deterrence, but won't provide any resistance. Pulling the rotor provides theft resistance, but no deterrence since there is no prior indication that there is a theft resistant force in play. Tracking and recovery aids are great, but are deployed later than desired. It would be best to keep the car from getting stolen in the first place. Who's got that for a non-Ferrari price?

Just call me Mark, Thanks for the pics. I've never seen that before. Ken, There's absolutely no way I would ever ever try to put those rods into place once the hinges are mounted on the car. If you managed to do that without screwing up your paint, then I humbly bow to your dexterity. Heck, I messed up the paint on my hinges and that was while putting them together on the bench. With the help of a BF vice... Sending you a PM as well.

Zedhead, I spent a couple cycles looking for an alternate booster from a different car that I could adapt to the Z, but I was pressed for time and didn't spend a lot of effort on it. The first big hurdle I encountered was that the booster for the Z does not have the input shaft location centered between the mounting stud locations. It's closer to the bottom than the top and seems to be unusual due to that. Things like the size and location of the vacuum port is no problem, but the mounting to the firewall is more difficult to deal with.