4 speed

was working on replacing the fan switch for the heat, when do I went on a 30-40 min ride, and although the fan was blowing it was cold air.
I stopped for gas a popped the hood, I could grab and hold the top radiator hose, also the heater hoses. as well lay my hand on the valve covers. the gauge showed it was only getting up to mark (not quite) between 100 and 210 (150*?). when I got back to the house I got out IR temp gun. top rad hose read 139*, alum intake on water passage by thermostat, 131*. its in the low 30s today, but could this be a thermostat stuck open?

1973, 350 4 speed, just an alum, other wise stock

MelWff

yes the thermostat is stuck open

ENCSDOUG

Try taking your radiator cap off when the vette is cold and start the motor. You should see no movement/flow in the antifreeze until the thermostat opens. If it starts flowing right away, the thermostat is stuck open.

The Punisher

Maybe you have 160 degree thermostat in there

mikem350

Use a 180 thermo for best oil and coolant temps

John 65

After you get the new one, boil it first and check it with the
IR temp gun.

I cant tell you how many defective brand new one's I purchased
that didn't open.

4 speed

no movement, even after 20 mins running sitting the driveway. but when I turned the cap to remove it before starting it gave burp/gurgle sound back to the catch can.

Rescue Rogers

electric fans or belt drive? whats the outside air temp? while its idleing take a piece of card board the size of your radiator and cover the inlet side of the radiator. If its a larger than normal radiator, low temp thermostat and clutch fan on a really cold day, it may take a long time to heat up. I had jeep with a 350 and a truck radiator that took forever to heat up.

the card board blocks the air flow which will heat up the water faster, not a solution, just a tool for trouble shooting, although tractor trailers used to do this with canvas covers back in the day

Mr D.

A lot of Vette owners would like to have your problem.

7T1vette

Thermostat is stuck OPEN or there is no thermostat in there at all. Either way, you have to open it up to fix it.

Rescue Rogers

He said the water isnt flowing at all

7T1vette

It can't be running "too cool" if water is not flowing. Now, if water is really not flowing, the temp gauge wouldn't be able to determine the level of heat in the engine (no water flow over the sensor); but the engine WOULD be running hot.

bashcraft

Are you going to stick that story?

The water doesn't need to be flowing for the sensor to work.

7T1vette

Heat transfer from air to metal is minimal; heat transfer from water to metal is high. Lose the coolant out of your cylinder heads and see how well your temp sensor works....

Why not converse with the OP instead of jawing with me.

jkippin

hmm how does an out side thermometer work?

op usually the thermostat will fail open so it cold be related to that. Card board idea seems plausible for too much air flow.
Yu did not say what type of fan it is or water pump. You did say its all stock engine so lets conclude that it is. IF the thermostat is missing or stuck open it will not give the coolant enough time to slow down in the engine to absorb thermal convection.

7T1vette

An outside thermometer works S-L-O-W-L-Y. If you want to wait while your overheating engine allows the temp sensor to read properly, you probably just 'cooked' your engine.

What is the interest here? Fixing the OP's problem or 'dickering' about details of temp sensor action????

jkippin

chill out dude
I think we all came to the same conclusion
I was just asking a dumb question something I've been curious about

Rescue Rogers

I like the part about the sensor not working cause the water isnt flowing, but anyway, the OP says he can grab the hoses and theyre not hot, the water isnt flowing and everthing else is. Have you tried blocking the radiator to raise the temp. Have you used a cheap laser temp guage to test the block temp

4 speed

sorry guys, my laptop crashed and havent been on. I took her to work on wedsday 2 hr and 15 min 80% highway, still can put my hand on the VC and its warm but not hot in the least, gauge reads the same and no heat. havent had the chance to pull the T stat yet.
but on that long of a trip I would think it would have warmed up ????

Rescue Rogers

not if the water is moving unimpeded and the outside air temp is cold. If you have a 150 or lower t-stat it wont get warm in this weather. If you cover half the radiator it would get hot since it does get warm. Pull the thermostat when you can and check in hot water on a stove to see when it opens with a thermometer. It should have the temp rating stamped into it. You should get a 185 stat and have it in case your s is rated low or is bad.