[n00b question] How to check coolant temperature?

This is embarassing to ask, but I'm wondering how to check the temp while the coolant is still hot; I'm wondering if I need to swap out my thermostat to increase the heater temp.

Thanks in advance.

 

You can get an infrared thermometer from Harbor Freight for about $15. Checking where the top radiator hose enters the radiator is probably the best spot to check for a comparison to your gauge. The stock thermostat should get the water hot enough for your heater. However they can fail open and prevent the engine from getting hot in the winter.

 

Question. If the Thermostat does not open shouldn't the engine overheat?

I agree some kind of thermometer is not a bad idea. Or put your hand onto the top of the rad that should be hot if you are willing to risk a burn.

 

Wouldn't a metal-probe meat thermometer work just as well?

 

a new thermostat is just about as cheap as buyin a thermometer.

 

I have plenty of thermometers, I just want to find out if I need to replace it. I have before, I just honestly didn't even realize you could buy them in different temperature ranges...or that running warmer was actually better for an engine. Not to mention, this is my first vehicle with no coolant temp gauge.

 

I have that...problem is, I have no idea what "Cold" and "Hot" are. Not to mention, I'm pretty sure it doesn't work. LOL. I'm still working on that one...the gas gauge is out, and I'll probably just swap out the whole cluster.

 

"I'll probably just swap out the whole cluster."

Before you go hog wild, try checking the simple stuff, like loose wires, poor contacts. Things are often a lot easier to tear apart than to replace.

 

I spent a while troubleshooting the gauge, wires, and sending unit with a multimeter, and from all the troubleshooting info we could find, we determined the gauge was the problem. From what I've read, it's advisable to swap both the coolant and fuel gauge simultaneously, and they're pretty expensive on their own. The speedo has seen better days for sure, and I was thinking that if I have to swap part of it out, I might as well save a little in the end and take care of it all at once.

Trust me, I'm all about fixing things at the smallest level possible...

 

Yes the engine will overheat if the thermostat does not open.
But - the engine will never heat up if the thermostat fails in the open position when the weather is freezing cold.
If the thermostat is not closing completely when it should or is failing to modulate the temperature at its set point of 185 degrees, it may be the reason infernalcolonel is not getting heat. His heater core could also be plugged. Checking multiple points thoughout the system with an infrared thermometer is the quickest way to find problem points. At worst their accuracy is plus or minus 4 degrees. Not only can you verify the action of the thermostat without breaking into the system and dumping coolant, you can also check out the in and out temps at the heater.