chaseincats

buy this and you're done: https://zcardepot.com/products/coolant-temperature-sensor-for-gauge-japan-240z-260z-280z#:~:text=$11.99,operates%20the%20coolant%20temperature%20gauge the end - I won’t be responding anymore since you now have the answer and a link to the part you need to fix the issue. Good luck

Ok, thanks for doing the test, now I'll move on - funny how you get a solution when you listen to us, huh. You have 1 test left - this will tell you if its the sensor OR the gauge that need to be replaced. Unplug that yellow wire you took a picture of and ground it against the engine block using an alligator clip/piece of wire/whatever. Touch one end of the alligator clip to the engine block (or any groundable area), touch the other end of the alligator clip to the yellow wire's metal connector, turn the ignition key to 'on', and look at the gauge: IF your gauge is good, the gauge's needle will move all the way right (250+). If that happens, your gauge is good, and your temp sensor needs to be replaced. If the gauge does NOT move all the way to the right it is probably your gauge. Replace the temp sender too though. This is the final test - it WILL give you a final answer.

I will not be responding to your posts until you try the tests I detailed many times. Sorry.

Your oil pressure is low because your oil level is low and looks like it came out of the labrea tar pits, 2000 years ago. I'm not sure what you mean by 10%, but I'm assuming its compression related. Neither of those are related to your temp issue. Let's work on the temp issue then deal with that afterwords. Since you don't have a thermometer in the engine, no need to let the engine sit and run for a while to warm up. Literally pop the cap off, turn it on and look if the coolant is circulating, then press down on the throttle linkage to rev the engine to see if the coolant also accelerates. Start to finish this is less than a 2 minute job.

Ok, so just to confirm - the car is now driving without a thermostat and you are getting the same 3/4 on the temp gauge that you got when the thermostat was installed in the past, correct? It that is the case, then the thermostat theory is out the door. Turn the car on with the radiator cap off and look to see if the coolant is circulating since the thermostat is off the car. Then press the throttle linkage to rev the engine and see if the coolant speeds up everytime you rev it. That will tell us if your water pump is working. Also, you'll know if you're low on coolant.

this is the oil you want

Hang on - the engine runs with the thermostat cover off and the coolant doesn't go all over the garage? If that's the case there is something dreadfully wrong with your water pump. The car running with the dipstick out is an unrelated issue. If the car runs fine with the dipstick out it means the car has a pretty large vacuum leak that a previous owner didn't find/look for and instead tuned the idle speed to compensate. Also that oil on the dipstick looks pretty terrible - I'd strongly consider doing an oil change asap

run it with whatever oil datsun recommends (I dont remember). Did you pull the dipstick to see if the oil level is low? running it without a thermostat can be detrimental in that there isn't a thermostat there to slow the SPEED of the coolant. meaning the coolant can be pressurized more than components are designed to hold. also, if the thermostat you have is working properly, then removing it (besides causing harm) will just be a waste of time. since you already have the thermostat out of the car, just throw it in a pot of hot water and see if that is your problem. all of those tests i wrote out literally take less than 10 minutes

A few things: Notes: check your oil level. at idle mine will sit maybe twice as high, but not that much higher. when you're driving, it should zip up to half+ Tests: if air isn't your issue then let's talk about the other ones Thermostat - since you already have yours out, lets test it. throw it in a pot of water on your stove and use a thermometer to see if it FULLY opens at 75c (use a meat thermometer or something in there to see when the water is the right temp). if not, your thermostat isn't allowing all of your coolant to cycle and that is the issue. I did this a while ago when i suspected my thermostat and that proved it was the issue. the thermostat keeps the car at a minimum temp, not a max one. if you remove the thermostat, it will get to 3/4 still...but it will just take longer if the thermostat is functioning properly Radiator: do you have enough coolant in it? Temp gauge: use an IR temp gun to see what temp your engine really is. I wonder if your temperature sending unit is just wrong. shoot the IR light on the temp sender plug area and see if it matches the gauge in the car

I got the Amazon pack and for those reading this in the future, you will want a 13/16th inch grommet

The amazon link Yarb posted should work since they are not already pass-throughs like the ones on harbor freight's page seem to be. Basically I redid all of the sound deadening in the car/floor but I am missing that grommet so I just hear all sorts of engine noise coming in through there which basically negated everything I did.

Hi all - I couldn't figure out the best place to put this question so hopefully here works. Does anyone know the size of the firewall grommet (or which Dorman one it is) that sits directly in front of the passenger seat (on the firewall)? This would be the one that sits on the firewall between the battery and engine.

That's great news. Any luck with the new fan clutch?

He doesn’t seem interested in testing that for some reason

Outside of checking the fan direction like folks were saying above, nope.

I've been thinking about this recently. What do folks usually do about this?

The factory manual says the spark gap can be set anywhere between 1.0 millimeter and 1.1 millimeter. I just wrote that instead of the thousands of inch measurement because it's shorter/easier to visualize for me. As a side note - when I removed one of the plugs last night, its ceramic surround cracked/shattered. It makes me curious if there were small cracks in it causing electromagnetic interference...or if really was just the gap.

I pulled the plugs and they were gapped to 1.0 not 1.1 even though I was sure I gapped them to 1.1. Just to cover all of my bases before I really went overboard with below-spec spark gaps again, I changed the gap to 1.1 and the car runs great. I don't understand why the car ran well at less than 1.0, poorly 1.0, and great at 1.1 considering factory spec is 1.0-1.1. Either way, we're sitting pretty now. Thanks all and hopefully this is the end of the drama!

oreilly sells rebuilt ones - why not just pick one of those up?

I have a cone air filter so it shouldn't be a mouse nest issue especially since it's kept in a sealed garage. It really should be the plug gap modification since it was an immediate change in power loss. I gapped all of the plugs because I dropped one (like a dummy) when I took it out and when I checked the others - they were all considerably smaller than the 1.0-1.1mm gap in the picture you sent from the FSM. If I had to guess, I might have done the Canadian gap by mistake back in the day. Is there a reason Canada uses the smaller gap?

I’m not sure what you mean, can you elaborate a bit?

Update for you: I noticed the spark plug gap was small (I believe .9mm but I don't remember how small specifically) so I gapped them all to ~1.1 which is the maximum gap in the fsm. The car seems to be considerably down on power and I need to press the pedal further to get the same power as before I messed with the gap. Oddly, the car idles noticeably smoother than before, it just is considerably down on power which doesn't make sense. Any idea why that would be and if I should reduce the gap to below 1mm like it was before?

If your condenser fan is wired to turn on with the AC, you may be able to test it without starting the car/belt fan by putting the key in 'on', turning the cabin fan on, then switching to AC. Confirming you have the fan shroud on? That is paramount for cooling.

yep that's the Aisin one - that didn't help me, only the one I linked to on Amazon brought my temp gauge to normal

Jumping in VERY late. I had a similar issue to this and changing to this fanclutch fixed it since it grabs harder than the standard Aisin one.