The Stovebolt Site Forums The Shop Area Engine Shop radiator Hoses / circulation

I have a 49 Chevy truck. New radiator and hoses. With the engine hot and running and heater on, I don’t see the thermostat opening and circulating. The top hose is hot 160 and the bottom hose is cooler 90 degrees. I measure with a laser thermometer. The bottom hose is hard and the top hose is soft when I squeeze it. I’m getting heat inside. My thermostat does not move and it’s a new one. I’m afraid the water is not circulating. Can anyone help?

I mean the water is not circulating when I leave the radiator cap off engine running 20 minutes

Not certain I follow you Robert, but if the top hose is hot, it indicates water is circulating. Feel the radiator. The top part of it should be hot and the lower part should be cooler. Leave your radiator cap on.

Hi Jon. Thanks for your answer. I’ll start her up and check.

Also, do you remember the temp rating of the thermostat you used?

Ok The temp at the top is 160. The temp at the bottom of the radiator is 105. I get plenty of heat. So the thermostat is working. But what about the temp gauge in the truck which is new.?

It’s an infrared Etekcity. Rated -56F - 716F

I don't know anything about that type of heat gauge, Robert. Sorry. I use the mechanical tube type which was in the truck when it was built. Where does your temp gauge get its reading?

Where ever he points it Jon. It’s a hand held gauge.

Need some more clarification Robert. You posted a question about the gauge in the truck but give temp readings from what appears to be a hand held temp reader.

What type of gauge is in your dash panel and whats the temp reading on it when your testing?
What is the thermostat's temp rating, i.e. is it a 160, 180 or higher degree thermostat?

The way the heater circuit is plumbed into a Stovebolt 6 engine some of the coolant is circulated through the heater core where it's cooled by releasing it's heat into your cab and the cooler coolant is returned to the water pump and recirculated in the engine. A heater core is basically a small radiator....
With cold outside temps this may be enough cooling to keep the coolant below your thermostat's fully opening temp. Since your getting 160 reading at the upper radiator hose the thermostat is atleast partially opening but may not be fully opening. This would be a OK if that is whats happening.
160 degrees at the upper radiator hose, good heat in your cab,no coolant leaks and 180 or less on your dash temp gauge = a good running Stovebolt 6 engine.

Maybe I'm reading post #1 wrong, but it seems that he's saying the dash gauge isn't indicating. The laser pointer readings sound about right.
Jerry

I agree with Jerry. Sounds like the dash gauge is not reading correctly. Sending unit issue?

roberts49chevy, is the gauge moving at all when warmed up?

Thanks for the answer. The in dash gauge is a stock temp gauge (100-212) correct for the truck. The thermostat is a 180. Everything seems to be working. I still cannot see the thermostat open with the radiator cap off. I do get plenty of heat in the cabin and I haven’t had an overheating problem. However the dash temp gauge won’t move. I installed a new gauge. I could have gotten a defective gauge.

You could try removing the gauge and setting the bulb into a pan of 200 degree water. If the gauge needle doesn't move (and assuming that bulb has been installed correctly into the head), the gauge isn't working. If you're not having overheating problems, it may be just a temp gauge issue. You do know a 180 thermostat sets a floor and not a ceiling on engine temperature, yes? Also in the winter in Rhode Island a 180 degree thermostat probably will work in very small increments...I assume when you say you can't see the t-stat open you are saying you don't see water coming out of the top hose, yes? Without some sort of special camera, I don't think you can actually see the thermostat working when it is installed and you also should know (as I'm sure you do) that at 180 degrees, a 180 t-stat will just begin to crack open. It won't be fully open until around 200 or a bit more. At 180 the t-stat may be only open by 1/16 inch or so, therefore the amount of water passing through will be small. If you want to test this, get a pan of water and a candy thermometer. Heat the water to 180, set your thermostat in and see what it does...if your temp at the top hose is around 160 or so, then the thermostat will just be dribbling water through the air bleed (jiggle valve) hole.

Good luck.