My 98'GS300 has had a problem with the cooling fans not turning on. A few months ago my wife drove the car while overheating and caused major damage to the engine. I didn't have the money to have the repairs done at a shop, so I did the work myself. I replaced the headgasket, valve stems, cam seals, exhaust and intake manifold gaskets, water pump, timing belt, valve cover seals, o-rings to name a few. I had the cylinder head resurfaced and cleaned. Even the intake and throttle body got polished up inside and out. It took me almost three months to disassemble and reassemble the engine back together. I finally started it up today and everything seems fine. The only problem is that the cooling fans still don't turn on. I installed new cooling fan switch, but that didn't solve the problem. If I unplug the the fan switch, then the fans turn on. What else should I be checking?

 

Sorry to hear that someone other than myself is having the same issue. Although I only changed my water pump, timing and drive belts, I still have the same issue as you after resembling the engine. With the car parked at idle, my heater does not get hot even after 20 minutes and the temp starts to climb a bit. I am still searching for answers as well.

This link is for the gs400 but Im checking my car right now to see if it applies.
https://www.clublexus.com/forums/sho...d.php?t=149626

 

[QUOTE=problem is that the cooling fans still don't turn on. I installed new cooling fan switch, but that didn't solve the problem. If I unplug the the fan switch, then the fans turn on. What else should I be checking?[/QUOTE]

You say fan switch do you mean relay? If you turn on your AC and the fans come on then I think your relay is okay. I am assuming that there is a "thermostat" switch that turns on the fans.

I hate issues like this. Your screwed with out the fans. If I where you I would not drive or at least make it so that when the car is running the fans are on.

BP

 

Did you check your T-stat, if it never opens than hot coolant from engine does not travel to the fan switch. Could also be a pluged radiator or something in the cooling system.

 

Im replacing my themostat today. I do believe this to be the problem (ok strongly hope). I had ruled it out because it still registers temp readings.

 

O MAN 76, when you say you replaced the fan switch, is it located on the bottom inside lip of the radiator?

 

NO JOY on the thermostat. The fans still don't engage with the new thermostat. So I'm leaning toward it being a coolant problem since the fans only work in conjunction with the AC being on. I'm flushing the system now. Any luck O MAN 76?

 

FIXED...

After replacing the thermostat, several coolant flushes and a cloud of smoke from the interior vents, I get the fires of hell at 85 degrees again and no temperature spikes.The fans are now coming on and off as they normally did before. I believe that fans require a certain amount of coolant to hit a certain temperature to operate properly.

Trying this helped
http://my.is/forums/f67/is300-coolan...refill-340999/

 

The switch I replaced goes on the bottom part of the radiator next to the transmission fluid line. It looks like a temperature sensor. The fans won't work even with the A/C on. The thermostat is also new. I'm gonna keep troubleshooting and resolve this matter. For now I'll drive with the fan switch unplugged, so my fans are constantly on.

 

could be just an air pocket...

 

I had a similar problem and after replacing the fan switch and getting an air pocket out of the cooling system, I have not had any further issues. I thought my coolant was full, but it actually took about half a gallon. Good luck with it.

 

Yeah...coolant levels are probably low.