Intermittent overheating?

Hey guys, got a question about my truck.

Truck: 87 Toyota mini- 22r, 4 speed, 2wd, 188,000 miles.

The problem I am having is that it intermittently overheats. In the winter it never has an issue, and only sometimes during the summer. The issue may occur randomly and at any speed. Stopped or at a slow crawl is much more apparent though. Until recently it wasn't an issue, but now it seems it gets hot 95% of the time. When I see it heat up, I turn the heat on full blast and try to draw as much off the engine as possible, which sucks when it is already 95 outside and I'm on a vinyl bench.

Anyways, I am leaning towards some sort of clutch on the fan or a sensor? I dunno, I don't want to just start tearing stuff apart with no reason. The truck runs great otherwise, and gets excellent mileage.

 

Do you hear the fan cutting in and out? The fan should run for a short time on cold startup and when the engine gets too hot.
Other things to look for are cold spots in the radiator, poor flow on the water pump, and bad thermostat.
I'm leaning toward bad clutch fan.
Better not get in the red, or you'll warp some aluminum.

 

I know it's practically unrelated but I have this problem on my focus too. Never on cold days but sometimes on hot days the temp gauge will fly into the red out of nowhere, then return to normal operating temperature a short while later.

 

The focus sounds like the thermostat is sticking shut, then frees up and works right again.

 

I've fixed that problem on a 20R and a 22RE.

I would follow these steps until it doesn't overheat any more:

1. Check the coolant level in the radiator. Add more if needed.

2. Replace the radiator cap.

3. Replace the thermostat.

4. Replace the radiator.


Since you didn't say anything about replacing them recently, I'm assuming that the cap, thermostat, and radiator are old enough to need a replacement.

If the radiator cap is venting when it shouldn't, the coolant can boil, and that prevents it from cooling properly.

If the thermostat is not opening all of the way, that can cause overheating.

Over time, the tiny coolant passages in the radiator load up with crud. When that happens, it looks like there's plenty of flow through the radiator, but it can't dump enough heat.

If you have to replace anything, drain the system and refill with premixed 50/50 coolant. If you don't use premix, use distilled water, not tap water. Also, if you don't use premixed coolant, make your own 50/50 premix, then put it into the truck. The wrong ratio, either way, will cause trouble.

I do not recommend using any type of coolant system cleaner. It's never helped me fix an overheating problem, and I believe that it may have caused damage.

I do not recommend trying to flush the coolant system. It's never helped me fix an overheating problem, and I've seen a lot more cooling system deposits from minerals in tap water than I have seen deposits from anything else.

I've replaced fan clutches to try to fix overheating problems, but it never worked. Unless you can see the fan clutch leaking fluid, I would leave it alone.

I don't know what sensor might cause overheating of a 22R.

I would leave the water pump alone unless it is noisy or leaking.

 

Here is what I have replaced thus far:
New OEM radiator about 3 years ago
I put in a new thermostat last summer thinking that maybe it could the culprit

I am going to check the radiator hoses, maybe they are collapsing once heat is built up. I am also going to replace the cap.