I'm having an overheating problem. At an Idle, my Z runs hot and just keeps getting hotter. I've hooked up to diagnose it and everything checks out. However, my secondary fan does not run when the motor reaches temp. Coolant is circulating, new thermostat, and oil pressure is great... any help?

 

I had to put an aftermarket fan control switch on my secondary fan when i ha dmy 91 z because the stock one bit the dust. My dad got mine at autozone so you might try there, i also swapped my thermostat out for a 160 degree unit. Also check your radiator cap and make sure its sealing.

 

Did this just happen out of the blue?

If not and you where just in there make sure it is full. Take the radiator cap off and let the engine get to running temp and you will probably notice the fluid level drop alot.

I had alot of issues lik this with my 89 that ended up it just being low on fluid and having air in the passages.

Also like said above I had to install a manual fan switch and just turn them on when it got hot.

It may be time to pull the radiator out and clean the years and years of grass,bugs, etc.. You would be amazed what you find in there if its never been out of the car. May even just opt for a new radiator if the car is worth the effort.

 

Seventeen year old radiator. Unless you've changed your antifreeze every 18 months, you could have a scaled-up radiator by now.
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Other things to check would be:
- engine timing
- Lower radiator hose collapse
- waterpump operation
- engine coolant temperature sensor. (I think the ECM turns on the second fan)
- Engine coolant temperature switch (turns on the primary fan)
- Proper operation of any solenoids that might be in the fan circuit
- shrouding intact?

 

secondary fan dosent run unless the air conditioning is on,, i could be mistaken it is 7am in the morning right now

 

your right, mine doesn't come on unless the A/C is on. its a 92 z.

 

ok so try that next time your overheating in traffic(dont wait till your overheating) turn on the a/c and see if that fan comes on if it does your having a problem with either your fan temp sensor. fan relay. or primary fan motor!