Lexus gs300 1994 overheat

If your 94 GS300 has high mileage as mine does check the following. If you have plenty of coolant, the belt has proper tension, the water pump isn't leaking, the hoses aren't leaking, then you may want to check to see if the pulley on your engines crankshaft has separated.

The harmonic balancer/ crankshaft pulley has been know to become defective on the GS300 after a ton of miles. My car reached the 350,000 miles mark before having trouble overheating. However, just looking at the belt and pulley spinning at normal idle with an untrained eye, you would not notice that for instance, the power steering pump pulley is rotating at a surprisingly low speed.

Take a socket and long handle ratchet or breaker bar and place it over the nut in the center of the crankshaft pulley. Allow handle to wedge up next to something sturdy; next, manually try to rotate the belt a few turns to see if the the nut in the crankshaft pulley rotates or not. If it does not then you have located the problem.

I hope this helps