Overheating in cold weather/ thermostat issue?

[WadiaAbushanab]

Hello, I think I am having issues with overheating/thermostat not opening on my 1980 Fiat spider carbureted. I had to recently bleed the cooling system but now having issues, it was fine before, but I also installed a new 32/36 carb and intake manifold dont think that would cause overheating. Anyways, as I drive, the thermostat inside the car will rise a little bit past the 190 mark, so I get out, and the bottom hose is cold. I let it sit while running until it rises to the end of the 0 on the 190, get out and now the bottom hose is hot, thermostat open. I start driving, itll cool off back down to 190 or slightly below, but then itll rise again. So i get out, and the bottom hose is cold again. Is it opening and closing constantly to keep the engine warm since its cold? Is this normal?

[Anbele]

Seems from your description that you might still have air in the system. There are several ways to tackle this, the most common one is to install a “T” in the upper most higher part of the cooling system lines. Which will be the hose that feeds into the top of the block at the engine firewall. Another one is to raise the front of the car as much as possible and remove the temp sensor at the front “T” located in between the cam pulleys and let the system reach normal operating temperature and bleed out though here. Kinda messy but effective. And of course, just to be 100% sure, you can do any one of these after replacing your thermostat with a new one—making sure it’s installed in the intended direction of water flow. Good luck!

[18Fiatsandcounting]

I agree with Anbele's suggestion that air in the system would be a good place to start. Also, you could have a defective thermostat or it could be installed in the wrong orientation. The easiest way to check the 3-neck thermostats is that you can blow into two of the necks when it's cold, but not the third. That third neck should be the one going to the lower radiator hose, and the other two are oriented so they match up with the short hose to the water pump and the longer hose up to the coolant T.

You can also drop the thermostat in a saucepan with boiling water, and you should be able to see the thermostat open up. As you remove the thermostat from the boiling water, it should slowly close again.

-Bryan

[WadiaAbushanab]

I agree with Anbele's suggestion that air in the system would be a good place to start. Also, you could have a defective thermostat or it could be installed in the wrong orientation. The easiest way to check the 3-neck thermostats is that you can blow into two of the necks when it's cold, but not the third. That third neck should be the one going to the lower radiator hose, and the other two are oriented so they match up with the short hose to the water pump and the longer hose up to the coolant T.

You can also drop the thermostat in a saucepan with boiling water, and you should be able to see the thermostat open up. As you remove the thermostat from the boiling water, it should slowly close again.

-Bryan

I took off the radiator cap so I could see flow once the thermostat opened up, but never saw any flow. It rose past 190, half way between 190 and 250, still no flow, but the bottom hose was hot which means the thermostat opened. Does this mean my water pump is dead?

[Nut124]

Did you touch the thermostat during the recent carb/intake work?

[WadiaAbushanab]

Did you touch the thermostat during the recent carb/intake work?

Nope, but there were coolant lines running through the old manifold so I had to refill the system with some coolant. But I’ve bled it so many times previous to this and it’s always fine always gotten the air. I don’t know why I’m having this issue now.

[18Fiatsandcounting]

I took off the radiator cap so I could see flow once the thermostat opened up, but never saw any flow. It rose past 190, half way between 190 and 250, still no flow, but the bottom hose was hot which means the thermostat opened. Does this mean my water pump is dead?

It used to be that you could remove the radiator cap on an older American car and see the water circulating down below the filler neck, but I have not seen this on Fiats. Usually the water just starts burbling out once the engine gets hot enough.

Water pumps do fail, but this is pretty uncommon. What is more likely is that you still have an air pocket somewhere, or it may be that you radiator is simply gunked up. Have you had the radiator cleaned recently? Another possibility is that the thermostat is opening, but not all the way.

-Bryan