Zed Head

Thanks LeonV, that's about where my thinking was ending up as far as how the tandem system worked. Except that for my 1976, the primary would be the first piston (the one contacted by the rod from the brake pedal), which would be the front brakes (the first, big, reservoir) and vice versa. So, essentially, if one system has air in it, the piston will run out of travel in its half of the bore before it can build up pressure to actuate the brakes, if the other system fails. That makes sense, and would explain the partial brake power - some pressure buildup but not enough. One good reason to shoot for a perfectly bled brake system, that I had not considered before. It's easy to live with a little extra travel in the brake pedal, but I didn't realize it would defeat the safety factor.

Sorry about the confusion, I was thinking of the wrong valve, the NP valve versus the warning light switch. And I'm still not clear on how exactly the NP valve works. Can't tell for sure how the tandem MC isolates front from back either, I will have to dig in to it. It sounds like you can have good brakes, but still not good enough for if one end fails. In 5th's case, the front brakes do most of the work anyway, so he should have had plenty of stopping power if the front and back are truly isolated. So it's not clear to me why he had essentially no stopping power when a rear wheel cylinder went out. Do the brakes have to be perfectly bled to be safe, rather than just feel like they work fine? Edit - just to add another thought. Both the brake warning switch and the NP valve have seals in them to isolate the fluids but to allow the transfer of some pressure, front to back and vice versa. Enough to move the switch for the brake check and to transfer some pressure for the NP valve. If the seals went bad, is it possible for the fluids to leak through? If so, you could have functioning brakes that are not isolated front to back. Bringing it up mainly for discussion, but also for safety.

After I read your story I thought the same thing that LeonV did and almost responded the same way. But, coincidentally, I had just bled my rear brakes so it was fresh in my mind that the pedal (in my car) will go all the way down if the back bleeder valve is open (similar to a blown wheel cylinder). I also checked the FSM and came to the same conclusion about how the master cylinder works. I wonder if the pressure differential valve is working correctly, on your car and mine? As mentioned, I too thought that it would isolate front from back if the pressure differential was too great, but my experience with bleeding the backs on my car, and your wild ride don't support that. Maybe our valves are not working right. I've searched the FSM but have not found where it says explicitly that it does more than make the Brake Check light go on. I'm curious, if anyone knows for sure. It would be worth tearing things down to fix that valve if it is supposed to be a fail-safe device. Edit - LeonV, I believe your story, just looking for more examples and insight. You might have had a slow leak that still allowed some pressure buildup(maybe?).

They don't look that bad. I got curious and I have a spare coil and a spare 12 volt battery and a spare coil wire. It's a 1978 280Z coil. 1.1 ohms primary (barely over spec. of 1.02 for 1978) 10 ohms secondary (in spec.) Connecting the positive side to batt. positive, and the negative side to the battery but with one end loose, and rigging the coil wire about .040" away from the negative terminal, tapping the negative wire to the coil negative gives a spark across the coil wire to battery negative. I found that it was easier to hear the spark than see it and that it worked best with a quick tap, not holding the negative on, then releasing it. Electricity is fast. If I held it on the the negative coil post for a second then took it off, I couldn't get a consistent spark. Maybe the coil can overcharge or saturate (?). I know a little bit but can't explain why that would be. If I sat there and tapped the wire to the negative post quickly I could hear the coil primary zapping the negative battery post each time. Anyway, with just a coil, some wires and a battery I could verify that I could create a spark. The coil is known to be good, I have used it before. Hope that helps. Your resistance numbers look like one of those coils, at least. should produce some sparks.

The same arm (or transverse link) is used for both sides so one will look upside down. Probably done for lower manufacturing costs.

Check your water temperature sensor. It's on the front of the thermostat housing. It might be loose or disconnected. How do you know that the thermostat "wasn't letting the water in" (it actually lets water out)? Was the engine overheating?

I'm not clear on why people run without vacuum advance. Even with a modern engine management system, MAP values are still used to control timing and fuel. MAP control is essentially like vacuum advance control. What is the reasoning behind getting rid of it, or is it more of a carb tuning thing? steve911t, I thought that your initial 1 - 5 list might have more value with engine RPM added. Can't really tell what the engine is seeing otherwise. Anyway, interesting discussion.

Yes. Some people use brass bushings from the hardware store. Use "shifter bushing" as a search term and you'll get several good threads. It's a common problem, the plastic ones crack and fall apart after many years.

Thanks oz c... Those might the only two I know though. I would still rather have a nice dial-back timing light and a few other extra tools. Necessity is a mother though...

I would get a second opinion from another shop. They don't seem very competent. A gasket plus silicone would be better than no gasket, just silicone. Their recommendation doesn't make sense. Plus they should have seen the deformation when they put the pan back on and suggested something then. They let you drive away with a deformed lip on the oil pan, that anyone with experience would know would probably leak. And, as a dealer, they should have easy access to any drawings showing the missing parts. They should fix it the right way, for free, but based on what you've said, that seems unlikely. Edit - I just saw your post over on Hybridz and the responses. Apparently Nissan has their own silicone gasket material that works well. Maybe that's what you dealer is suggesting, and maybe it will work. They still should have got it right the first time. Oil pan sealing is pretty basic stuff for a professional shop.

One way to measure your mechanical advance is to hook up your timing light, start the engine, disconnect your vacuum advance hose, retard the timing to zero (once you've confirmed the damper mark), then rev the engine up until the timing stops advancing. Your timing tab probably stops at 20 degrees, so you should get a direct reading of total mechanical advance. You will probably have to adjust your idle up to keep the engine running with the timing retarded. Then you can temporarily connect your vacuum advance hose to manifold vacuum,while you're set to zero timing, to see what your vac advance canister pulls. If your pulling over 14 inches of vacuum through the intake you should get the full vacuum advance at idle without increasing rpm. Since you're at zero, you'll get a direct reading off of your timing tab. Some simple tricks for seeing what works and how much, if you don't have the nice timing light or degree marks on your damper.

Have you checked the manufacturer's recommendations, or installation instructions? Delrin is a plastic known for "natural" lubricity, like nylon. In other words, it's already slippery.

Fuel injectors "tick" also. L engines are known for mechanical noise, from what I've read, with their non-hydraulic valve system and noisy fuel injectors. Some people like it. When you wrote .080 you meant .008 right? .080 would be noisy.

Another way to do it, in similar fashion is to bring the piston up to a known depth from the spark plug hold (like when something in the hole just starts to move), make a mark on the damper, then go over TDC and let the piston drop down to that same distance on the other side and make another mark. Split the difference between the marks and you'll have TDC. The piston doesn't move up or down much around TDC but the damper does so you can be quite a ways off in crankshaft rotation trying to estimate when the piston stopped moving up or down.

Sounds like you don't trust that "Zero" = TDC on the compression stroke. Why do anything else until you know? If you find that it's incorrect, but the damper is in good condition and you know why the mark is wrong, you could just make a new mark.

True. I was just suggesting what should happen with a good one. Plus he's tried three coils so something is awry. Patcon, are you sure that you're grounding the coil main wire to a good ground. Wouldn't hurt to confirm the path back to battery. Just guessing.

Spammer alert. Selling EBay stuff.

Where are you looking for spark? You should have the main wire from the center of the coil disconnected from the distributor with either the cover pulled back so that you can see the metal end, or a bolt or something stuck in there. The end should be about a spark plug gap away from a good ground so that you can see the spark jump when you tap the coil negative to ground. I might be stating the obvious but if you have power through the coil posts (the primary circuit) and you're seeing a spark when you tap the negative to ground, you should see a discharge from the main center wire of the coil if it has a gap it can jump to ground.

It sounds like your Auxiliary Air Regulator (AAR) is stuck closed (if it's still there,some people remove them). It is designed to let air past the throttle body to keep the idle up when cold. Your engine has an Air Flow Meter (AFM). Technically it might be called a mass air flow sensor but that is not how they are known in the Z world. I have not heard of anyone rebuilding one themselves, but am interested in how you do with it. Both of these items are covered in detail in the Factory Service Manual (FSM). It is worth reading at least the first few pages of the Engine Fuel section before diving in to engine problems.

Sounds like the piston in your master cylinder is bottoming out in the bore. If so, it might be starting at mid-stroke in the bore. This would not let the bore fill with fluid, so would not pump any through the lines. You might have the rod in to the master cylinder adjusted to be too long. Adjust it to as short as necessary to get play in the linkage. Make sure that master cylinder piston is coming all the way back. Just one possibility.

That connector might be your "brake warning lamp check relay". Looks like the relay on the lower right of the picture. Does the red "brake" light on your speedometer face light up with the key on but engine off? Injection seat sounds painful... Glad I don't have one.

That actually sounds like a good way to check it as long as you don't short something to ground with your screwdriver. That's how they work in use, opening and closing about 9,000 time per minute (150 times per second - can't believe it myself but that's the math) at 3,000 rpm engine speed. You should set dwell or point gap more precisely though once you know it works. The setting can affect your spark power, I believe.

As I understand it, "points" are actually short for contact breaker points. Current flows when the points are closed, when they open, breaking the circuit, the magnetic field collapses causing the secondary circuit to discharge. But I am not an expert in the field (pun intended!) and just writing those words made me uncomfortable. The FSMs all have procedures for testing the coils. It involves just measuring resistance across the primary circuit and from the primary to secondary contact points. Resistance values are given. You might check your points to be sure that when they're open no current will flow and vice versa. I don't think coils go completely bad that often, they are pretty tough unless overheated.

Year of car and type of ignition system (points or electronic) would help. Otherwise, you might get many random guesses. I think that coil actually sparks when the ground is removed, breaking the primary circuit. The coil charges when the negative side has a circuit to ground, through the points or the ignition module, then the secondary circuit sparks when the primary circuit is broken. I have had it backwards myself in the past, I can't speak to what Fastwoman has said. The end result is the same, assuming there was no path to ground to begin with. Either way, touching the coil negative to ground should charge the primary circuit (with 12 volts coming in through the coil + passing through the primary windings and to ground), then removing the wire from ground should break it, causing a spark at the main terminal. So you probably won't get a visible spark unless you break the coil negative path to ground.

I agree with ER on the idle speed change indicating the booster leaking vacuum. Is there a hissing noise also? The pedal going to the floor could indicate air still in the lines or a leaking cylinder, most likely the master if you don't have fluid leaking from the wheel cylinders or calipers. Or as bgm suggested, your rear brakes are out of adjustment and you're just pushing the wheel cylinders way out of their bores. The calipers are self-adjusting but the back drums are not. Does the parking brake handle come way up or does it set tight and low? If it comes way up, you can try setting and releasing it several times. Otherwise, a screwdriver through that little hole on the drums, or remove the drums and turn the wheel. It sounds like you have the same problems you started with. Bummer.