I have a 94 pickup 3.0 V6. It has started overheating when idling with the heater on. Once I start driving it quickly drops back to normal. It has never got into the red area, but really close. Would this be a thermostat issue? Any help would be appreciated it. Thanks

 

My past experiece with your situation is a dirty/clogged radiator. Not enough air is moving to cool the fluid. I would go thru the entire cooling system.

 

Not a thermostat problem. If it was thermostat, it would overheat while moving too. Driving = moving = ram air flowing through the radiator. Idling = no ram air. Not moving depends upon the cooling system belt-driven fan to move air through the heat exchanger (radiator). There is a device that couples the fan to the shaft that rotates it. This device slips under some conditions (speed and temperature). It tends to to lock-up at lower engine speeds and higher temperatures. Simple explanation of the system. Your "fan clutch" probably needs to be replaced. Simple job. I'd buy a genuine Toyota part if I would be doing the job on my truck. Parts store replacements are probably considerably cheaper though. My $0.02
simple on a 22RE, I don't have experience with the V-6.

 

air flow issue....
Is the fan shroud still in place? Is the plastic fan even turning?

 

Yes the fan is turning. What is the fan shroud? Thx

 

Its a plastic cover above the fan to protect it and you when in operation.

 

Here's a drawing (second page) http://web.archive.org/web/201311071...11radiator.pdf

The "no. 2" shroud (the thin strip at the bottom) isn't TOO critical, but if the rest of the shroud is missing I would expect the problem you're having.

The fan clutch will spin the fan even when it's hot and "disengaged," but it may not spin it fast enough. With the engine off and the clutch cold, it should feel "pretty stiff." Replacing the clutch is a pretty simple job, but the part is $170-$250 online http://www.toyotapartsoverstock.com/...621065030.html , probably around $300 at your brick-and-mortar dealership. A little steep, in my book, to replace on a guess.

I've never seen an "aftermarket" fan clutch, so if you find one let us know.

 

rockauto.com Toyota -- 1994 -- pickup -- 3.0l V8 -- cooling system -- radiator fan clutch

take your pick. There's not an easy way to check one of these, but if its not sucking air strongly through the radiator while vehicle static, engine idling, and temp indicator out of the green and rising...it ain't no good. Use a piece of paper or light cardboard at the face of the radiator. How to select among the offerings on rockauto? List 'em here, and the cognoscenti will let you know. My $0.02

 

I concur on possibility of fan bad clutch.
Ensure that shroud is in good condition. This will ensure that airflow from fan is focused on the radiator and that heat from the radiator is focused on and is sensed by the fluid coupling (fan clutch).
Then observe how closely the fan follows engine/pulley speed.
Here's how I did mine... After stopping from a drive at operating temperature, I let engine idle for 5 minutes. This helps ensure that forced/ram air from highway speed is no longer cooling the fan clutch.
Turned engine off and counted number of seconds until fan also stops. Fan stopped about 2 seconds after engine stopped. This is on a new fan clutch.
Bad fan clutch with weaker coupling would stop later. [YOUTUBE] [/YOUTUBE]

BELOW IS EXAMPLE OF BAD FAN CLUTCH WHEN FAN CLUTCH IS HOT
[YOUTUBE] [/YOUTUBE]