Hello. I have a '91 3000GT VR4 with an overheating issue.

Background: It was purchased from a dealer auction. It has 64k original miles, never wrecked. Timing belt and water pump replaced 150 miles ago.

The temperature gauge will read well over the 3/4 mark, yet the cooling fans won't turn on. Parts I've replaced include: Radiator, radiator switches that screw into the bottom of the radiator, temperature sending unit to the ecu (thermostat housing area), thermostat, fixed some small leaky hoses, gently flushed the heater core.

The vehicle's heater works just fine, both fans turn on when I activate the AC compressor. No signs of a leaky head gasket or cracked heads.

I own an infrared temperature gun. After the in-dash gauge surpassed the halfway mark, I checked the temperature at the thermostat housing, at the top radiator hose where it meets the radiator, the front cylinder head, the front cylinder valve cover, the engine block, the radiator itself... all temp readings were below 200 degrees, most readings were around 185-195. I pulled out the overflow tank hose and did see some drops dripping into the tank.

The vehicle has plenty of power, but according to the in-dash gauge, it will quickly overheat, within a minute or two, once driven. At idle, it'll take 10 minutes or so for the in-dash gauge to indicate overheating. That is, if the in-dash temp gauge is working correctly.

I've checked the fan relays, and fuses and wiring on the passenger side, but not on the driver side fender. I'd like to check all of the ground wire(s) that relate to the cooling fan(s), but I don't know exactly where they're located on this vehicle. Also, I saw Riskeavr4 mention checking wiring at the *** connector, where is that?

Any help is appreciated, this car is driving me bananas.

 

I must preface with the statement that I'm not familiar with electronics of the 3000GT, but Monteros have a similar temperature gauge behavior. On Montero the gauge reading will shoot to hot and stays there for some time (while the engine running at totally normal temperature), then gradually goes down to normal reading. It turns out in most cases it is just a malfunction of the circuit board behind the temp gauge on the instrument cluster. There is a DIY re-soldering fix for this on Montero (you can check the threads there for this topic). As I said, I do not know if 3000GT could have the same behavior, but based on your description, readings and all the parts you replaced it makes me wonder if this is just an electronic fluke.

 

relax that will work for the 3000GT as well.