Time to change the thermostat?

[Larry T.]

Using an IR temp gun I got the following readings:

Upper radiator hose: 160-165* (remained at 160 until the temp gauge on the instrument panel hit about 205, then went to 165)

Thermostat housing: 197* when temp gauge hit about 205*

I do not know what thermostat I have. I am guessing that it either is not opening all the way if at all or may be a thermostat that is too high a temp range?

It seems clear to me that it should be changed but I want to know if I should be checking anything else.

During the winter the car ran plenty cool, never hit 210*. Now that it is warming up (70-80*) it is getting to 210 fast and pushing over a bit in heavier traffic. Here in South Louisiana it is only going to get hotter. Last summer a few minutes of idling caused it to push past 210 in a hurry and got hot enough to overflow a couple of times.

FWIW I have gone to manifold vacuum and my initial timing is 12*. Engine is an L72.

Thanks.

[Stephen L.]

Re: Time to change the thermostat?

A faulty (closed) thermostat will cause the engine to overheat. Yours appears to be working. You may have a 195* thermostat installed......

Another cause of overheating in traffic (very slow speed) is the fan clutch. Test the clutch by running engine, shutting it off, then watch the fan. It should stop in a turn or two if the clutch is working properly.

A partially plugged radiator can also give you fits in warm weather. Using your IR see if you can detect "cool" areas on the radiator with the engine hot and running which may be an indication of plugging.

[Larry T.]

Re: Time to change the thermostat?

Fan clutch stops pretty quickly. It is hard to get to different parts of the radiator with the shroud in the way.

I drove the car and it got up to about 215*. I checked the temp at the hose and it had jumped up 20* to 185*. Presumably the thermostat opened up. I am going with the idea that I probably has a 195* thermostat for now. I will change it to a 180* and go from there.

Thanks,

Larry

[Joe R.]

Re: Time to change the thermostat?

Larry,

Does your car have the A.I.R. option? If so, the 195 degree thermostat is correct for your application. If not, 180 is the one you want. By the way, the thermostat won't set the max temp, once it has opened fully the radiator takes over. It sounds like it may be time to pull the radiator and have it serviced by a competent radiator shop.

Joe

[Ronald L.]

Re: Time to change the thermostat?

If the most the car gets is summer driving what is wrong with a 165 thermostat?

[Larry T.]

Re: Time to change the thermostat?

Larry,

Does your car have the A.I.R. option? If so, the 195 degree thermostat is correct for your application. If not, 180 is the one you want. By the way, the thermostat won't set the max temp, once it has opened fully the radiator takes over. It sounds like it may be time to pull the radiator and have it serviced by a competent radiator shop.

Joe

It could be a radiator issue, but I am beginning to think maybe the thermostat is not opening all the way. I will change the thermostat and see how it works out. Next step will in all likelihood be a stop at the radiator shop.

If the most the car gets is summer driving what is wrong with a 165 thermostat?

I drive this car year round. Mild winters in the deep south mostly make up for the miserable heat in the summer. Isn't 165 too cool really?

Thanks.

[Joe R.]

Re: Time to change the thermostat?

Larry,

I think the 180 degree thermostat is the best choice unless you have AIR. Check out this link:

https://www.forums.ncrs.org/showthread.php?t=69615&referrerid=2667&uid=2876

You might consider the Robertshaw flowkooler thermostat, here's more info:

https://www.forums.ncrs.org/showthread.php?t=76745&highlight=thermostat&uid=5394

Joe

[Ronald L.]

Re: Time to change the thermostat?

Question guys:
I had a thermostat int he car, put it is water on a heater and a thermostat.

cracked at about 165 - by 180 clearly wide open.

Friday bought a new one from Paragon 180 degree. This new one in the same water, did not even crack until 195 and by about 200 was wide open.

I did this three times to see if it would change or there was a water user error.

No way.

Which one should go in the car, this 1966 427? the original that is wide open by 180 of this "supposed to be a 180" from paragon?

[Joe R.]

Re: Time to change the thermostat?

Ron,

It sounds like Paragon sent you the wrong thermostat. Unless you have the Air Injection Reactor (AIR) system, you want the 180 degree thermostat.

Joe

[Wayne M.]

Re: Time to change the thermostat?

If the most the car gets is summer driving what is wrong with a 165 thermostat?

Or, at least Larry T. should try a 160 (like the C1's had [?] -- see pics) and measure the parameters, same as he's done for the Paragon "180"; then install temporarily to see how temp gauge behaves during the warm-up cycle and heavy traffic.

[Ronald L.]

Re: Time to change the thermostat?

The Paragon part, made in USA is stamped 180, 180 on the box just does not open at 180. I put my old part back in because by 180 it is wide open.

I had seen in other posts here that the 160 thermostat was not reccomended due to temp fluctuations, etc.

Not really sure about that, at idle, I finally go the gauge (out os the dash0 reading 210 and a thermometer int he top rad liquid was measuring 220. hood closed, idle 20 minutes.

HOT!