Why Is My Nissan 300zx Overheating When I Have My Air Conditioner On

Posted in Air Conditioning

Alright here I go, The car is a 91 nissan 300zx na 2+2. the problem i am having is that my car starts to over heat after about ten minutes of having the air conditioner on. but if i turn it off and i am not in stop and go traffic the car will still stay warm, not hot. it will stay inside the lines about 3/4 of the way up. but if i leave my ac on the gauge will continue to clime but after i reach 3/5 of the way i shut it off and turn on the heater to relieve some of the heat and roll with the windows down. but if i accelorate to rmps above 3.5k it will drop rapidly evan if it is in netral. I have replaced the water pump, timing belt all of the cooling hoses, the radiator, thermostat, alternator, all the drive belts, front oil seals, oil pump gasket, transmission fluid and filter, head gasket, valve cover oil seals, upper and lower plenum seal, fuel injectors and connectors, vacuum lines, upgraded air filter, spark plugs, and ac compressor oring. and that car is still not running right. there is no coolant leaks, I checked it with a Snap-on coiling system tester and held pressure at 15 psi for over night. i cleaned the condenser and removed all blockage. also the only part of the cooling system i have not replaced was the belt driven fan which i will soon replace. so any advice will help alot except some one telling me to get a new car lol. thanks!

There are 3 Answers for "Why Is My Nissan 300zx Overheating When I Have My Air Conditioner On"

    1. Nova73guy says:

      One of two things could be the cluprit. If it’s a mechanical fan then the clutch could be going bad, and not allowing the fan to draw air across the radiator. OR… When you replaced all of the parts, it’s possible you didn’t get all of the air out of the system. When you say the temperature drops when you accelerate, it sounds like there’s still air trapped in the system and it’s not allowing the sensor to get a proper reading while you’re just cruising around town. Try bleeding the system again and check the fan clutch.

      Oh, and don’t get a new car. Stick with the Z31 as long as possible!

    2. John Paul says:

      The only thing I do not see is a new radatior a bigger unit fron Howell or CRC. Sounds as if you cleaned the debris out from between the a/c condenser and the stock radator? before you replace that old cracked fan blade and fan clutch: go online Flex-A Lite electric cooling fans much better, 300ZX and twin turbo should never over heat even down here in Texas… You know the cooling system is intact (snap on pressure tester held) BUT is the pressure cap holding pressure 9 psi minium and 14 psi even better… Coolant antifreeze water ratio? 60% water 40% antifreeze summer 50% X 50% winter let’s talk if you want [email protected]

    3. Answerrack.com says:

      First you A/C will work the engine hard causing more heat, always use Max A/C for Maximum Efficiency(that is just a tip)
      If you have a Fan Clutch on the car, with the car off and cold, spin the fan by hand, if it rotates more than 540 degrees or one and one half times, it should stop around one turn to be real good. then the fan clutch is no good.
      That will be your whole problem right there, just because it is spinning while running the clutch can be totally no good.

      When you changed the water pump, did you check the ports behind it for blockage, I say that because if anyone who owned the car either yourself or someone else, if they or yourself have ever poured radiator sealer or headgasket sealer in the radiator it can clog those ports up over time, it can take years but that stuff will come back to haunt you with clogs.

      Your symptoms are that of a bad fan clutch, exact symptoms.

      The clog would probably not come down with the temperature so fast, but will cause a problem like you have.

      Also if anyone removed the fan shroud that needs to be on there to pull air .