VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 1938 Chevy MD Temperature Gauge - Where is 180?

Hi, I am trying to determine if I have an overheating issue. With a temperature probe in the radiator (160 thermostat) the water temperature stabilizes at 179. However, the needle on the temperature gauge is square on the second to last dot. The left dot with the line connecting the left and far right dot. I don't know how to upload the picture I took.

Does this sound correct?

If the turkey at Thanksgiving tastes like anti-freeze, only I will know why.....

Thank you!

Brad

The beginning of the line is 200 deg. and far right is 212 deg.
180 deg. will be just past the 1/2 way.
Get a cheap infrared thermometer gun and aim it at the head next to where the temp. line screws in.
The dash gauge nevers reads too hot but can read too cool as they age and loose their accuracy.

Wherever it reads must be 180 if that's what the coolant temperature is. If I remember right 180 on my Master is about 3/4 the way over.

Hi;

That's where I'm going with this. I think I have a clogged water jacket near the temperature probe. I do not know the where the probe is relative where the corrosion commonly occurs in the water jackets, but the temp gauge is reading way higher than the actual coolant temperature.

Maybe the gauge is just off. But if that is so, why does it puke coolant at operating temperature?

I will investigate further as you suggest.

Thanks!

Brad

If the water jackets ARE NOT FULL OF RUST something is wrong.

Update on the overheating.

With the engine coolant stable at 180 degrees (160 degree t'stat), the temperature gauge in the dash reads 200 degrees. The infrared temperature at the temperature sending unit in the block is 205. The infrared temperature just above the intake manifold reads 205 on all six cylinders. Coolant starts to puke from the radiator overflow tube when the dash gauge hits 200 degrees. Infrared temperature of radiator core is 188 degrees.

What's all this mean? I am guessing the water jackets are not flowing. They should be at 180 degrees.

The good news is the original engine is in the shop getting rebuilt and next summer I will swap motors.

Too bad, I was looking forward to doing some car shows this summer.

With a 160 thermostat the coolant temp. should be 160 Deg. except if the engine has been idling for a period of time, car not moving or out side temp. above 75 Deg. or so.
Your radiator core is restrcted with rust, as 99% are.

Have your radiator cleaned and flow tested. You could find that you might need a new core.

Hi;

I should have mentioned this. The radiator is brand new!

But it could have rust from the block restricting the flow.

It helps to have all of the information needed so that your question can be answer accurately. Anyway, since you have a new radiator, and IF the flow isn't restricted by rust from the water jackets, then the radiator can probably be eliminated from the problem.