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If it's not overheating but just running a little warmer than you would like, try diluting down your coolant a little with water to see if it helps. Standard mix is 50/50, try 40/60 or less. More water/less coolant is more effective in cooling. Also, as already mentioned here, look for fine debris like lint or dog hair on the front of the radiator behind the condenser. You'd be surprised what you find there, and might be losing up to half the cooling capacity. You wont' be able to see it unless you remove the radiator as the debris accumulates in a circle in middle.
 

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Simply put, the thermotime switch controls the cold start valve. It acts as a timer to prevent the cold start valve from staying open too long and causing the engine to run very rich (flood). View attachment 108749
Thanks for clarifying that for me. Great indo!
I really need to start digging into my 76 FSM lol

Bon
 

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If the nissan dealership just connected the pipe coming out of the back of the cylinder head with a piece of hose connecting the circuit to the water pump inlet. That will increase your operating temperature. I may not be understanding what they did, but when deleting the heater core, the hose should be capped to prevent the hot coolant at the back of the head just running to the water pump inlet.
 

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did you ever test for a leaking head gasket? Just cause you have a new one on a recent build does not mean its not leaking.
If the Rad is old as the car it maybe partly plugged up. I replaced mine with a new and it helped. If you can find a shop that is able to recore the orig that would be best. Don't let them just rod it out, get a new core. IF you cant find a good shop then buy a new one, but stay away from an aluminum. You can get new brass and copper rads, that is what I did.
 

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did you ever test for a leaking head gasket? Just cause you have a new one on a recent build does not mean its not leaking.
If the Rad is old as the car it maybe partly plugged up. I replaced mine with a new and it helped. If you can find a shop that is able to recore the orig that would be best. Don't let them just rod it out, get a new core. IF you cant find a good shop then buy a new one, but stay away from an aluminum. You can get new brass and copper rads, that is what I did.
hey Dave,
is there any reason to stay away from aluminum? I prefer stock myself, but I was planning to go aluminum in the future. what gives?

Thanks,

Bon
 

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my prob with alum is its hard to fix, I broke down on the road back in the 1970's with a Z, a garage shop got me back on the road with some solder (the water pump broke sending the fan into the 1st row of the rad). Besides the easy to fix I have a issue with how cheap they are. 140$ seems to be the going price, I cant see how a decently made rad can be had for that. Makes me think they are poorly made and likely to fail. I suppose you could find a high end TOTL alum rad that is well made (expensive), but most of those seem to be for racing. Unless there is a need for racing parts (ie actual racing) then it seems a waste as the engine was designed to use the stock type rad and works fine as long as everything else is correct. I have AC as well, seems like the alum rads do not do well with the stock shroud, shrouds are really important when idling in traffic with the AC on (again back to the racing where no shrouds are needed). I think a lot of folks use super high capacity rads to mask an underlying overheating problem that has nothing to do with the rad. When I see one of those that is the 1st thing that comes to mind.
 

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Forgot to mention, I noted my temps would sometimes go over the 1/2 way mark on the gauge, which in my case is pretty accurate (checking it vs a thermometer). This was with a 170f Nissan thermostat. After some driving in hot weather with AC on I decided my T stat was opening fully and the rad was the variable (on cooler days it would run at about the "E" of TEMP). I 1st took the rad to a shop where the supposedly rodded it out. I don't think they did a good job. there was no change in the behavior of the cooling pattern. Next I purchased a brand new brass and copper rad, think it was about $225. It had the correct fitment (had to do only some very mild trimming on one flange side) and the correct placement of the drain. Shroud fit was ok. I came with the overflow on the passenger side (my 75 was on driver) which allowed me to run an overflow tank. Since running this rad I have had sustained high speed runs as well as traffic with AC and the temp runs noticeably cooler, rarely getting out of the E and never as high as it did with the old rad. I did have some issues at idle that I tracked to the fan clutch, but at speed its never gets as high as the old rad did. I suspect my old rad was partly plugged up (I could see deposits still in it AFTER the rodding out). This is why I suggest a NEW core regardless if the shop says they can rod it out. I think this is the best option IF you have a good shop that can do a recore, it just makes fitment a non issue.
 

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Thanks for that input, Dave. I agree.
I always find it funny when I see these guys online, youtube, etc... who got these giant 4 row alum rads in their stock Zs. I always say, if you're racing (I mean true track racing, not mindless street racing) then perhaps go big alum. Personally, I have always had good luck with the stock nissan style copper radiators. they flow just fine. whenever I have a cooling issue, it's almost always something else... failing WP, defective clutch fan, running with no shroud, busted or bad hoses, dead thermostat, etc.
the only reason I wanted to get an aluminum was because I wanted to have it powder coated, as copper cannot survive the high heat process of powder coating.
I think I'll just stick with what works best.... what Nissan designed the car to have.
Thanks again!

Bon
 

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My main reason was I do a lot of LONG trips, I just trust the copper/brass more not to fail.
That's awesome man.
I did a 2,700 mile trip in my 280zx from Utah out to North Carolina and that car ran like a champ.... stayed cool the entire time. it was great!
Even the stock radiators on my Z31's are good... I drove my NA 87 for four years out here in the UAE (four crazy hot summers) and never had an issue... and the rads on those are only single row core! The nissan design quality at that time was fantastic. I better stop highjacking the OP thread haha.
Thanks again.

Bon
 

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My wide mouth borg warner tropical thermostat got a good test Saturday. 87 degrees and never wavered past E on the temp gauge. Last year with a 180 thermostat it would go to M frequently. Tail of the dragon 2 years ago to the right of M. Eek.
 

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My wide mouth borg warner tropical thermostat got a good test Saturday. 87 degrees and never wavered past E on the temp gauge. Last year with a 180 thermostat it would go to M frequently. Tail of the dragon 2 years ago to the right of M. Eek.
that sounds like a monster stat. what degrees is it? the stat
 

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I think the middle of the e was right around 165-170 back when I was checking it. My last really long trip was the Orlando to pikes peak run in about 4 days (round trip). It was early sept IIRC and pretty hot in kanas and MO, with the AC on going 80 I would get abit over the middle point. this was not normal so I spent a lot of time with the AC off which would bring it bac to below middle of the gauge. Clearly the rad was controlling the temp not the t stat. Anyway since then I have replaced the old rad with a new copper brass, longest trip has been only about 400 miles in one day, but with AC on going 70ish it never gets past E. I again figured it was a partly plugged up rad (I could see deposits at the filler neck I can only imagine it would be at least as bad down on the bottom of the rad). One day I may get to removing the tanks and really examining the old rad
 
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