Over heating car - Need some help

My 1980 Tercel has been runing like a champ but it slowly started to run hot (nothing bad but generally the temp read below the middle line and slowly it started readind above the mid line).

Suddenly, last week, it started to overheat bad. I have to run the heater in traffic to keep the engine from getting too hot and even then, temps are getting very close to the red.

Long story short, the electric fan is on %100 all the time and blows strong as ever. The coolant is topped off, the belt is turning the water pump, and no strange noise emitting from the pump.

The radiator is cool to the touch after driving for almost an hour but the top of the radiator and return line are hot as hell.

I am thinking a bad thermostat but was wondering if anyone else would know what would cause this. Thanks.

 

Not too much help here, I am just amazed you managed to keep an '80 Tercel running good this long. You are the man.

But it sounds like the thermostat could be a possiblility. You can check one easily if you take it out and place it in boiling water to see if it is failing to open up (to allow circulation) when hot.

 

Usually when thermostats go bad they stay open. Allowing the coolant to constantly flow. It wouldn't hurt to change it though. They're cheap.

It's possible the water pump is the culprit. It may seem fine, but the fins internally could literally be corroded away. The shaft spins, but doesn't pump any coolant around.

Has it ever had the coolant flushed?

 

I'd swap out the t-stat as mentioned and the rad cap, both cheap and easy to try.
My old bike had similar symptoms and it was the cap, wouldn't hold pressure causing the coolant to basically boil and overheat.

 

When is the last time you replaced the radiator itself? You might wanna look there.if its half or totally plugged it will cause an overheat.you seem to have covered the most obvious reasons.had this happen once,replaced damn near every component in the cooling system and the car still overheated, turns out in the end it was a plugged radiator core .replaced the radiator,problem solved.Oh, and don't bother trying to flush it a lot of times in these old radiators the only thing keeping them from leaking is the sludge inside them.do yourself a favor and purchase a new 1 if you can find it.

 

Check the hoses, sometimes a hose will collapse at operating temp and your fluid can't circulate

 

Thanks though the rebuild credit goes to my brother. He gave the car to me when he moved. It had almost 600k miles before the rebuild (I think 575ish)

Yeah, the rad cap is bad but the fan generally kept water temps down regardless. Not a big/hot engine

It used to drain and I would fill the coolant every 6 months I fixed that about a year ago.

Radiator def needs to be replaced. On the list of things to do.

But it should be pretty audible if the water pump fins brake, yes?

Hoses are good.

Thanks for the inputs! Did some further reading, the hot tube runing from the engine and the cold tube at the bottom of the radiator generally can mean one of three things (I got two of them from your comments).
-Thermostat stuck closed
-Bad pump
-Clogged rad

Ill start with the thermostat as thats the easiest. The water pump only has 30k miles on it so should be ok. The rad is original and had a few small hair line fractures in it over the years. Gonna need to be replaced one of these days.