your thoughts on thermostat function..

[Mike Miller]

When i was in trade school back in the early 70s they taught us the importance of the thermostat and what usually happens without one.. however now i have to wonder if a 180 thermo will actually do more harm than good compared to the 195. My 74 Charger has a 1970 Plymouth 440 drive train in it and the previous owner(s) who did this switch were not big on small details like wiring for example. I have a 26 inch radiator with a 18inch 4 blade fan that sits 3 inches from the radiator. I installed a shroud that seems to help with the high engine heat and went from the 195 to the 160 to see if it would help with the high operating temp. The car runs right in the center of the gauge for about 15-20 minutes at 55mph.. then the gauge starts to "flutter" slightly and the temp slowly climbs right to the hot end of the gauge. The coolant system is super clean inside and the coolant is diluted to 20 degrees above as i live in the South and it does not freeze here. The question is.. if the motor runs at say 200 degrees no matter what and you drop down from a 195 to a 160 thermostat would the 160 get overwhelmed due to less cooling time in the radiator as opposed to the 195 having a longer cycle? It seems like that flutter indicates that the thermostat is being overwhelmed and just stays open allowing the engine to heat as though it has no thermostat at all?? I got a 6 blade fan and a 1inch spacer today and will try that before i revert back to the 195 thermostat again. I tried 2 180 thermostats, different brands and they both do the same thing. Process of elimination will get me where i need to be but i wonder if anyone has any thoughts about this.. sorry bout the long read !! P.S. i know about the lower hose collapse problem.. will look into that more closely.. Thanks .

 

[snakeoil24]

I would add a clutch fan and I’m going to follow this closely

 

[pnora]

Are you sure the radiator is 100 percent? You can check with a pyro for hot and cold spots. My experience with restricted radiators is the heating problems you are having. Does running the heater help lower the temp at all?

 

[RemCharger]

I would question the integrity of the stock gauge circuit. Have you temp gunned the engine?

 

[Lefty71]

Once its open, it's open when it's hot out, if you know what I`m sayin.

 

[Fran Blacker]

Is your fan half in half out of shroud?

 

[diesel_lv]

The temp on the thermostat is what it "starts" to open at. They are fully open 15° above that. 160-175, 180-195, 195-210. My '67 383 w a/c n 26" radiator was stock 180°. The amount of blades on a direct drive fan at 55 mph "can" have an effect. However, on a stock 440 w all components being good, it should not creep up while going 55. I am currently running 26" 2 row aluminum, 11 blade 19" fan, fan shroud, flowkooler pump and 180 t-stat on 496" stroker w a/c. In AZ in 115-120 outside temps, I run about 176-180° at 80 mph. It just stays there. When I slow, it'll raise a little and settle at 196° in-town light to light cruising. I'd verify my engine temps w a temp gun.

 

[PlymCrazy]

I’d definitely get a 2nd temp reading from an aftermarket gauge. And check the ignition timing. That can have a noticeable impact on overheating issues as well.

 

[diesel_lv]

Here's 174, 196 and 222 on a '67 gauge.

 

[Jerry Hall]

Your radiator can still be the issue. Even though your coolant is clean and you have flushed the system, it can still have restrictions. I had the same issue on my Superbird with all stock components. Pulling the radiator and having it taken apart and the core rodded and cleaned it never heat soaks. I run a 160 thermostat and the temperature runs a needle width above 170 on the gauge now.
A heat gun to various places on the radiator will tell you if you have restrictions.

 

[MoparLeo]

Fan clutch, proper fan blade. fan should be at least have way into the shroud opening. Use a refractometer to properly measure the coolant %.
20° above means almost no coolant as normal freezing point at sea level is 32°. Use only distilled water. Ethylene Glycol. on cast iron head/block engines.
Check your radiator cap (normally 16 lbs.) and pressure test cooling system. Make sure to burp out any air pockets in the cooling system, this will cause the temp to roam and run hot.
The Functions of a Radiator Fan.

 

[HawkRod]

The thermostat has NOTHING to do with you cooling system's ability to shed heat - all it does is regulate the engine temperature, ASSUMING YOUR COOLING SYSTEM CAN SHED THE HEAT.

So if you had infinite cooling capability, a 160* thermostat will cause the engine to run slightly above 160*. Same thing for a 180* or 195*. On the other hand, if you are running a 160* thermostat and your engine is running at 200, your cooling system isn't getting rid of the heat.

Do you have a shroud? This is critical for good cooling. Your problem is somewhere in your cooling system.

 

[jamie]

Check your distributors mechanical and vacuum function to make sure it is working as it should. Replace rad cap too. Is it puking coolant? Check that lower hose.

 

[Ranger16]

Changing from a 195° stat to a 180° and adding a shroud brought my temps down from 200°+ to 180°. I'd agree with the radiator being the problem.

 

[Mike Miller]

I added a shroud as there was none when i got the car, it wasnt run for years at the time when i bought the car so who can say how long it sat ..the fan is mostly out of the shroud so i bought a 1 inch spacer and a 6 blade fan which i have not yet installed.. looking into the radiator i found some rust flakes but barely any. The lower hose does not have a spring and searching local autoparts stores nobody carries one that does. I have to reference a 1970 plymouth fury 1 for the hoses because thats what the drive train came out of.. the lower is a Gates 20663. I have been looking into the whole clutch fan thing and will go that route if i have to, not a big "fan" of that idea.. { sorry } I am having a new trans put in soon and i will have the shop professionally flush the coolant system. They replaced the freeze out plugs in the block as they were paper thin. They also rebuilt the differential and i dropped down from 278 (?) gears to 355 (?) with a posi unit. With the engine running at higher speeds you would think it would run cooler but the heat has been a problem ever since. I borrowed a heat gun and will use it when i reassemble later today. The engine only puked once and alot of fine rust came out after i flushed the system afterwards. With no coolant recovery system my guess is it might of had too much coolant and spit out the rest.. and it was 98 degrees here at the time as well. The gauge seems accurate and i replaced the sending unit as well. It repeats each time so its at least a good reference. Than you much for your input !!

 

[Mike67]

The ratings on a thermostat are really a timing function to get the motor up to operating temp ( what is was engineered for optimum efficiency). If you live in a colder climate a 195° degree will open later allowing your motor get to operating temp, in the south where temps where cold weather isnt as big of a factor.

 

[72sunroof]

When i was in trade school back in the early 70s they taught us the importance of the thermostat and what usually happens without one.. however now i have to wonder if a 180 thermo will actually do more harm than good compared to the 195. My 74 Charger has a 1970 Plymouth 440 drive train in it and the previous owner(s) who did this switch were not big on small details like wiring for example. I have a 26 inch radiator with a 18inch 4 blade fan that sits 3 inches from the radiator. I installed a shroud that seems to help with the high engine heat and went from the 195 to the 160 to see if it would help with the high operating temp. The car runs right in the center of the gauge for about 15-20 minutes at 55mph.. then the gauge starts to "flutter" slightly and the temp slowly climbs right to the hot end of the gauge. The coolant system is super clean inside and the coolant is diluted to 20 degrees above as i live in the South and it does not freeze here. The question is.. if the motor runs at say 200 degrees no matter what and you drop down from a 195 to a 160 thermostat would the 160 get overwhelmed due to less cooling time in the radiator as opposed to the 195 having a longer cycle? It seems like that flutter indicates that the thermostat is being overwhelmed and just stays open allowing the engine to heat as though it has no thermostat at all?? I got a 6 blade fan and a 1inch spacer today and will try that before i revert back to the 195 thermostat again. I tried 2 180 thermostats, different brands and they both do the same thing. Process of elimination will get me where i need to be but i wonder if anyone has any thoughts about this.. sorry bout the long read !! P.S. i know about the lower hose collapse problem.. will look into that more closely.. Thanks .

Have you tested for leaks with a pressure tester?
Have you tested your Guage to make sure it is accurate?
What water pump? Ac pumps move the water slower.
I had engine builders when I was younger tell me to run 195 "so it would cycle" I have it in my 72 Charger 340 0.30 over that with the fan being 1/2 in the shroud keeps it on the lower half of rhe range even with the air conditioning on in summer in Florida. Under normal operation you can watch the gauge fluctuate.
I Run 50/50 to make sure boil point is elevated.
Engines need heat to run well, just not too hot.
Never seen a modern lower hose collapse, you test by someone running the engine up to 4k and watch, but I doubt anything will happen.

 

[Mike Miller]

I ran the car with the 6 blade flex fan,shroud,180 thermo ,fan halfway into the shroud etc and i will say the air that was being pulled thru the front of the radiator was incredible!! Driving the car i could see the system cycling as the thermostat opened and it stayed well within the normal range of the gauge. I also ran the heat gun all over the radiator, water pump, hoses, and thermostat housing and nothing was over 190 degrees.. so far so good.

 

[WileE]

You need a 5, 6 or 7 blade fan that sits centered in the shroud opening.

 

[Mike Miller]

It sits centered both in depth and diameter to the opening.. being a flex fan seems to be frowned upon alot here but when i can find the right clutch fan setup i will likely go that route..right now i am trying to figure out why the new fan belt i put on squeals under power and it seems the lower pully has been replaced by p/o and looks to be about 3/16 of an inch out of line with the water pump/ p/s pump.. now i have to hope i can find another outer damper pully somewhere.. finding parts has been a challenge !!