so today while driving around my temp gauge was doing something very weird. it would go from the middle all the way to hot and then back to the middle. is this an electrical issue or was it overheating? its really hard to tell if it was over heating or not since i dont have a coolant temp gauge

 

It is your engine coolant temperature sensor. (sometimes called a master sensor) If you have a 400 it is the electrical connection by the inlet tube from your radiator. check the connection and sensor. I think you can get the part from an auto store for under $20 and you can do it your self.

 

cool thxs so much. i actually drive a 300 with a 1j swap so is the location of the sensor still in the same spot?

 

well found out it wasnt the sensor...it was actually overheating! looked in the radiator and there was not coolant. topped it off with water, started the car and was driving fine. then when i parked it i found a water leak. it appears it was coming out the water pump. oh joy! -_- gonna work on that this weekend. hopefully its the o-rings and not the pump...

 

Glad ya found it. I had the same issue minus the leak. What was it? Air in the system

For such a simple layout these systems are quite a ****** to bleed. (1JZ specifically)

 

how long did u overheat for? you could already have damage to your head gasket

 

hardly overheated at all. i would stop preiodically and let the engine cool down cause i wasnt quite sure what was going on and i wanted to be on the safe side.

 

if your already gone be in there you might as well replace the water pump since its prolly never been changed
so you wont have to worry bout it for a good 50k miles or so
just my opinion though

 

its looks brand new but i know what your saying. i've been pondering that for a good couple days whether i should change it out or not even if its just an o-ring leak