Hey guys. 1993 SC400, at idle (stop lights, in park, etc.) my temp gauge will get to halfway, or slightly above, and normally stays there. But recently at idle it has been rising rapidly past the halfway mark. As soon as it's in drive and I accelerate it levels out. Water neck seems to have slight seepage as there is a little bit of dried up pink coolant around it. But that has been the case since I've owned the vehicle and it's never done this. I did replace the cold start injector time switch and the actual coolant temperature sensor (just the one at the engine, not the one on the radiator) when trying to fix another issue months ago. Coolant is completely full with clean 50/50. Any ideas? Faulty gauge arm, malfunctioning coolant temp sensor/thermostat?

 

Seepage means you have a leak and air pockets with a system that can't handle pressure.

Fix the leaks, use a lisle funnel kit and top off the coolant and allow it to get up to temperature so the thermostat opens and you get the air bubbles out. You will want to have your car with the front end higher up (like at the start of your driveway or ramps)

It shouldn't rapidly rise past the halfway mark

 

Have the cooling system pressure tested to make sure there are no leaks whatsoever.

Thermostat might be the next move.

 

First and foremost, when the temp starts rising ... make sure your fan is running.

 

Huge sincere thanks to all the savants on here always making me feel like an idiot lol. Stupid amount of air in the coolant system, I changed out the thermostat and water neck with gaskets and burped it all out, running smoother than ever. I am still curious about my fan though. It turns on and runs but I don't ever notice it kick into a higher speed, like when it's up to temp or anything like that. Is it pretty much one speed all the time or is there a certain threshold at which it kicks on? Either way, my present issue is solved at least, it sits right at half almost all of the time now. But if anyone has any insight on the fan let me know!