Question about an overheating truck.

Factual Questions
1

I have a 1995 Jimmy. When I’m riding down the road, the temp gauge is fine. But when I come to a stop light, it goes up to about 220 degrees. The funny thing is, while I’m at the stoplight, if I put it in neutral and press the gas and get the RPMs up to about 2200, the temp gauge goes back to normal. I guess because that’s making the fan rotate faster, right?

So, what could be causing the temp to rise in the first place? I put a new thermostat in about 6 months ago, but that doesn’t mean it couldn’t be a defective stat. It’s just weird that when I’m riding along, nothing is wrong with it. No smoke, the temp gauge is fine and no smell.

I checked the belt and it seems tight, I checked the radiator and nothing seems to be awry with that.

I’m thinking it could be the water pump or it needs antifreeze. But if it was the water pump, wouldn’t it just blow up and not work at all? Why would it work halfway oronly when the RPMs are high? That’s why I’m not leaning towards that TOO much.

What are your suggestions and your take on this?

2

Didja check your oil? When my van gets low on oil it acts just like that…

3

Water pump with eroded impellers, clogged radiator, or too little coolant.

4

First, check the coolant level in the radiator (cold engine only). The overflow jar is not a reliable indicator of engine coolant level. If it’s low, top it up and see if the symptom ceases, then find and fix the leak.

Second, check the fan clutch operation. It should get stiffer when it reaches a certain temperature.

5

Unless I am mistaken, a 1955 anything won’t have an overflow or a fan clutch.
The only thing that maintains air flow through the radiator at idle is or was the fan shroud. They are (for anything before the late 60s) made of sheet metal and normally vibrate and rust off pretty quick.
The solution I used on my old dodge powerwagon was to get an after market electric fan after market electric fan and remove the original fan (replacing the bolts so the water pump still turns) .

6

It says 1995.

7

Oops, My misread.
Then it is most likely the Electric fan, Fan thermostat or something causing the fan not to come on.
Easy test: When you get somewhere you can stop and it is ready to overheat, open the hood with the engine running and see if the electric fan is running, it is on the engine side of the radiator. If it overheats without the fan coming on, the problem is the fan or thermostat for sure. May be a blown fuse or bad connector to the fan, but that is less likely.

8

It has a belt driven fan, so the fan clutch is the likely suspect in that area.

9

Thanks fellas. I’m gonna look at the fan mechanism tomorrow. I put more antifreeze in it tonight, but haven’t driven it yet. Man, frickin cars…something always needs fixing. I just replaced my power booster for my breaks 3 DAYS AGO !!! Ugh…