When was radiator cap last changed? So you say overheated - what are the symptoms? What do you use to accurately measure the water temps?

 

Many questions before jumping to solutions.

• During your time of ownership of this car, did it once work properly (never overheated)?
• Was any work done on the car immediately prior to this problem being noticed the first time?
• For all the parts you replaced, were they all Toyota OEM parts? If not, what aftermarket sources did you use?

If this car never operated properly during your ownership, it is possible the prior owner put the thermostat in backwards, and you replaced it and installed it the same way the prior one was put in.

Given your lower radiator hose never gets very warm/hot, it would seem you have little if any coolant flow through the radiator. It is possible your radiator is mostly clogged internally, so the little that does flow is cooled very well (as the radiator is not getting hot) so the very low flow out of the radiator is quite cool, but not a sufficient enough flow to take the heat of the engine away.

The fact that you have heat is a very strong indication you have coolant circulation within the engine, meaning the water pump is working properly.

Would be good to get answers to the questions above.

 

I've seen the $5 rad cap be the culprit.... Those litttle plastic disks break off that seal it under pressure.

 

Just fixed a cooling issue on my son's Ford. Culprit was debris blocking the external fins on the radiator.
Look between the a/c condenser and the radiator spray it with a hose opposite direction of air flow to remove.
Also replaced rad cap due to collapsed top rad hose. Runs great now.

 

PROBLEM RESOLVED: Moral of the story, always start out with your ODB2 reader. I ended up replacing the t-stat, but that was not the problem. Nor was the problem the water pump, radiator, or a blockage. What tipped me off where a few things: after the car cat overnight, it was very very difficult to start; in fact it did not start. I opened the hood, and let it sit in the sun for a bit. Hours later, i try again to start it, this time is spluttered to life. Ran like shit. I notice, immediately, the temp gauge was at operating temp! I was like, wtf, I just started this thing. Stopped the engine. Got my scanner out (mind you, i ran the engine for 30 seconds or so), and read the live date. the ECT (engine coolant temp) was 86C. Ahhh, that ain't workin', i just started it, no way it was that hot already. So, I replaced the coolant sensor, which was an easy repair, and boom! problem solved. It wouldn't start because the temp sensor told the engine to lean out baby, i'm hot! when it was not hot.

 

That's good news. Glad you found the problem without firing the parts cannon at it.