chaseincats

I agree with no definitive answer until then. I will post some observations in the interim though.

All makes sense. Since I did a leakdown test and didn't see any bubbles in the radiator & used a combustion gas tester, how else would I check for a head gasket leak if there isn't any mayo in there either?

I did that early on after running radiator flush through the system. A good amount of stuff came out for sure. Do you think its worth doing again?

Not since I've owned it 7 years ago. I did do a leakdown test to make sure no combustion gasses were entering the coolant through the head gasket and the head gasket came back as solid. There isn't any chocolate milk under the coolant/oil caps.

Gotcha. He suggested changing back to an OEM style thermostat and if that doesn't work to knock out the back-right freeze plug (the one above the starter) and flush the engine out again through the thermostat housing. He said IF there's rust in the block, it usually sticks around near that freeze plug.

It has a brand new 3-core radiator. Everything on the cooling system was changed.

Right. The old OEM thermostat opened 20 degrees later than it should have and even at well over 200 degrees didn't fully open. The aftermarket one reacted more along the lines of the brand new oem thermostat but it's opening isn't as large and the plunger travel isn't as far since it is physically smaller.

I did not. I felt that since the car will have a thermostat regardless, testing one to confirm it works as advertised before putting it in would negate that test especially since I confirmed the original OEM one was broken and the newer aftermarket one is more-or-less defective by design.

UPDATE: I spoke with my old Z mechanic to see where he got the OEM thermostat that was in the car before my changeover to the new aftermarket one earlier this year since OEM ones are supposedly NLA. It turns out Nissan still makes a thermostat that works but is not the original one designated for the car. This thermostat is a Nissan part (part number 21200-F3190) but works in a bunch of their engines (L-series included). This is the thermostat that held the car's temperature at 170 from 2015-2020 before I started having cooling issues. I threw the old and new OEM thermostats as well as the aftermarket one in a pot of water. The old OEM thermostat started opening at 185 (unlike the new OEM one which opened around 170) and after continuing to heat the pot, the old OEM thermostat only ended up opening about 2/3's as much as the new OEM thermostat so the old OEM thermostat was indeed bad. The aftermarket one opened and closed at the same temperatures as the new OEM thermostat but the opening indeed is about 30% smaller than the OEM thermostat and the amount of travel the plunger can physically move is again maybe 30% less due to it being physically shorter. I have not tried the new thermostat in the car because driving it around in this cold weather won't give me a definitive answer, but I am feeling confident that my old worn-out OEM thermostat not opening at the right temperature (and not to the right amount) started this issue, and installing an aftermarket thermostat that physically can't move as much coolant as an OEM one kept me heating up, but for for a different reason entirely. With the new OEM thermostat correcting both issues, we should be all set come spring time. Here are pictures of the OEM one (right side) next to the aftermarket one (left side). You can see the opening is considerably smaller and plunger's travel is considerably shorter on the aftermarket unit. I will update you guys in the spring. I don't understand how/why they sell this design...

I've been asking in a variety of ways if the spacer is needed to have the gap between the body and tire identical on the front or rear. I haven't received a yes or no yet.

Oh, so the spacer would be necessary for the car's rear not to sag then it seems?

I haven't actually. That said, I have the considerably lighter (23 lbs) 77/78 bumpers so I don't think it would change the ride height as much as it would have with the 74-76 ones which were ~90 lbs each.

Any idea without the spacer, would the vehicle sit level with the ground or would the rear sag compared to the front?

Sorry if I'm not explaining my question well. What I am asking is if I put 4 of the standard strut mount insulators in and ignore their 260/280z-only rear insulator spacer (or any other donut/etc spacer) in there, will the rear wheel gap (good call on that metric) be greater than, less than, or equal to the wheel gap in the front?

It sounded like from your post/the fsm pic that adding their spacer to get back to 'stock' ride height for the 280 gave it a rake out of the factory where the body was higher in the back than the front and not using the spacer would get you/us a level-sitting car, no?

Gotcha, so in this case, to have a level car like a 240/260/any other car, the spacer isn't needed.

Since they increased the ride height on the rear of the car for the 280 means that when it was sold new it had a bit of a rake to it where the rear was higher than the front then?

Hi guys, I was reading that the 280z's rear strut mount was higher than teh 240's and requires a spacer (this part). If I don't add this to the car, does that mean the front will sit higher than the rear or did the 280z have a rake to it when new?

Good catch, I should have added that I did pressure test the cooling system and radiator cap when I installed all of that new hardware a few months ago. I also did a leak-down test yesterday and besides finding out I have a few tired piston rings, I confirmed there isn't any combustion gas leaking into the coolant.

The car has a new radiator and water pump and before I did that, I flushed out the rust (in theory) with the radiator flush chemical a few times and did the old 'hose in the thermostat housing' routine.

I've heard from a bunch of sources that the smaller opening of the aftermarket thermostats compared to the OEM one (and apparently now this) hinders cooling. That's the case at least (probably) on my car.

I'll give that a shot, thanks! Has anyone tried this thermostat in a world where the OEM one is NLA?

Update for you guys. I spoke with my old Z mechanic and he said (and I've heard from a couple folks on Z forums too) that aftermarket thermostats don't flow as much coolant as an OEM one. Has anyone else here heard of this or is it more of a wives tale? I took my old Nissan OEM thermostat and popped it in a pot of water and the 170 degree thermostat didn't start opening until 185ish so I'm guessing that was bad and the new one which is aftermarket isn't large enough to flow enough coolant for a steady temp. Can anyone recommend a 170 degree thermostat that flows as much coolant as an OEM one? Currently the thermostat I have is this.

Hi all - Wondering if anyone knows where the fuel pump ground wire terminates in the car. The pump has two wires going into the wiring loom but the service manual says one of them terminates directly to a ground. Any idea where that hides on a 1978?

Hi all, I just put a Dynomax SuperTurbo 17733 on my stock 280 and it is noticeably quieter than the (what turned out to be magnaflow) muffler that was sawed off. I took a look under the car (no cat) and I believe the below is a resonator (correct me if I'm wrong). Do these need to be removed when using the SuperTurbo muffler? The car is almost EV quiet after swapping the magnaflow with this.