Over heating issue

[91chevyburbbeast]

Hey everyone! Umm yeah got a problem obviously my old 91 Chevy Burban that frankly has me scratching my head. This just started yesterday. I find that she starts to over heat, so I turn on my heater to suck some of the heat off to get off the road and the heater blows cold. Then all of a sudden my temp gauge will drop back to the normal running temp and my heater returns. I was originally thinking it was the thermostat getting sticky but there is a voice in the back of my head saying that’s not it dumb dumb. So I figured I would reach out here. Also the coolant recovery tank has coolant in it so I’m rather sure I’m not low but I could be wrong.

 

[Scribbles]

First and foremost you need to check coolant at the radiator not at the tank, most likely your coolant is low and the heater core is getting air pockets causing the heater core to not have coolant for the heater and also air pockets in the radiator causing the over heating.

 

[91chevyburbbeast]

Ok could that cause a sparatic over heat to normal temp?

 

[Scribbles]

I think so, if your radiator is full then I would look at the water pump and then the fan clutch, but I would put money if you are filling the coolant tank and not checking the radiator itself then you’re not doing any good.

 

[91chevyburbbeast]

I haven’t filled it. It’s just got fluid but I’ll check the radiator after work. And let you know thanks

 

[frankin5]

check the cap as it is what controls fluid to and from the recover tank. The cap not functioning will not pull fluid to replace that which is missing. As said above check and fill the radiator as needed first. Then have a pressure test on radiator and cap.

 

[imiceman44]

I think so, if your radiator is full then I would look at the water pump and then the fan clutch, but I would put money if you are filling the coolant tank and not checking the radiator itself then you’re not doing any good.

That's exactly what happened to mine. You could have a slow leak or a bad cap that caused the fluid to go to the rank and not come back.
I have had both happen.
Pressure test your system if no leaks it's the cap.

 

[91chevyburbbeast]

Ok I’ll check that out. I did top off the radiator it was low but not empty but low at that. I’ll run it for a few days and recheck it.

 

[imiceman44]

Ok I’ll check that out. I did top off the radiator it was low but not empty but low at that. I’ll run it for a few days and recheck it.

It probably is still low, you need to put the heater on hot and run the engine till it warms up.
You were experiencing a no coolant in the heater core wjen it was overheating and blowing cold.
It starts with gaps in coolant flow until it gets low enough no coolant can get to the heater.

 

[dyeager535]

Ok I’ll check that out. I did top off the radiator it was low but not empty but low at that. I’ll run it for a few days and recheck it.

If you have coolant in the overflow, and the radiator is not full, there is something wrong. Either the cap is bad, or the overflow line/tank is plugged up and not allowing coolant back into the radiator as it cools. If there is junk in the tank (stop leak is one I've seen) it can act as a one-way valve, allowing fluid out of the radiator under pressure, and preventing it's return as the engine cools.

 

[imiceman44]

If you have coolant in the overflow, and the radiator is not full, there is something wrong. Either the cap is bad, or the overflow line/tank is plugged up and not allowing coolant back into the radiator as it cools. If there is junk in the tank (stop leak is one I've seen) it can act as a one-way valve, allowing fluid out of the radiator under pressure, and preventing it's return as the engine cools.

Also if there is a leak in the system, it can't suck back the coolant frpm the tank.
It has to hold vacuum.

 

[Carcinogen]

Also make sure you actually have a recovery tank and not just an overflow...

 

[chulisohombre]

Everyone’s pretty much covered it but I’d say the cap isn’t opened my or the overflow is clogged. You can blow air into the drain hose on the overflow with the radiator line unhooked and see if the coolant returns out the other end. That’s how I figured out mine was clogged with stop leak. Hose is cheap to replace that line as well if it looks warn or cracked.