your thoughts on thermostat function..

[oldkimmer]

I can tell u my experience with changing thermostats. 75 or so Plymouth Salon. 318,904,8.25 diff with 2.71 gears. It always ran slightly over half on the gauge with a 195 T stat. I changed to a 160 stat. Drove by 20 or so miles and the temp started climbing. The farther we went the higher the gauge went. So then I changed to a 180 stat. Was better. Made about 50 miles and the gauge started climbing higher again, a bit better somewhat. So I put the 195 back into it, car was happy again. I always run a 195 stat, even in my race car. I had an old guy back then tell me that he came to the conclusion that Mopars had a marginal cooling system. Kim

 

[Geoff 2]

A book could be written [ maybe two! ] about cooling systems. I had a Dart that would overheat & boil if high rpms were used in 1st and 2nd gear. No problem if only 1st gear revved out.
The problem [ took a long time to find it ]: the corregated flex hose I was using for the upper hose. The inside was not smooth, had corregations. This was aerating the coolant at high rpms...& air is a poor heat conductor. I mention this as an example of how strange things can happen.
Things to think about:
- the stat # [ eg, 160 ] is the opening temp. Full open takes a further 20-30*.
- cruising at 60 mph produces twice as many heat-producing-power strokes than at 30 mph. But the same amount of coolant has to try & dissipate that extra heat.
- some shrouds are poorly designed & act more like baffles at high road speeds.
- the fan blade tips need to be close to the shroud if the shroud is to be effective. Obviously at some point when that gap gets too big, the benefit of the shroud is lost.

 

[MoparForLife]

I doubts it’s just your thermostat. My street wedge was running really warm here in North Texas. When I asked a local radiator shop who’s been in business since the 50s, his reply was priceless! “Those Yankees in Detroit under engineered the cooling system especially on the big blocks. They had no idea what it takes to keep a car cool on a hot, humid southern day! Those things overheated when they were new.”

So I attacked the problem on multiple fronts and it’s now running in the normal operating range. I used a Mr Gasket thermometer radiator cap and IR thermometer when I was troubleshooting.

You can read my post to see everything I did but in my opinion, the change that made the biggest dent in the running warm/hot issue was upgrading to the Glen Rey Ultra Cool option and adding the FlowKooler water pump.

Also, I noticed a slight drop after fixing a vacuum leak under the dash in my heater control switch. I had to reset the timing and play with the carb adjustments as a result of the vacuum leak.

Good luck!

PS - when I’m not showing the car, I replace my upper hose and use this filter, I’m still getting debris and rust on a regular basis from the block.

 

[Norv]

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 .

I had a 69 road runner back in the 70's. I took my thermostat out and it ran just fine.

 

[RJRENTON]

I had a 69 road runner back in the 70's. I took my thermostat out and it ran just fine.

What was the temperature (both ambient and coolant and driving conditions being compared) b4 removing the thermostat; and what was the results, using the same variables and conditions, AFTER removing the thermostat? "It ran just fine" means nothing.....without further info. Sort of like the phrase "without pictures" shows nothing.
BTW.....You cannot just slow the coolant thru the radiator...to allow it to give up its heat, WITHOUT the coolant that remains in the block and heads from gaining more heat (aka super heating) with the water pump running at a given RPM. The thermostat's sole function is establish the MINIMUM operating temp. Once the thermostat opens, cooling ability is a factor of the radiator's total surface area and the gallons/minute and velocity the coolant is circulated.....given the radiator surface area is fixed, the velocity and pumped volume is the only remaining variable, in addition to the ambient temperature entering the radiator.....which the vehicle owner has no control. Moral of the story: faster or more circulated volume (gal/min) and velocity (ft/sec) per unit of time, the greater the Btu's/Hr will be exchanged. Its that simple...
Just my opinion of course...
BOB RENTON

 

[Ron H]

My age-old understanding is the T-stat rating has nada to do with a overheating hassle unless it’s not functioning (as another posted). Removing the stat entirely wasn’t recommended as the coolant flow through the radiator is accelerated possibly exceeding the capacity of the radiator to do what it’s intended to do – remain long enough through the rad to cool the coolant. A bud took his stat out having no ills until a car cruise we went on with a long slow ride with frequent stops to get the cruise chain through the course. Oh well, he still runs it w/o a stat rarely encountering heavy traffic. Had some irritating hassles prodding changing from a 4 to 7 blade fan, finding an OEM shroud, both were options on my old ride I didn’t have. As well, added another option, a top seal a fellow member suggested. Reduced the coolant ratio adding wetter reading that coolant can be a heat demon and since my car hibernates in a heated garage, not a concern. A higher stat, good for cold weather climates, traps coolant in the block longer so ya can get heat/defrost sooner. In hot weather, why would there be need to elevate the motor temp faster unless ya want to do burn outs quicker?

Came across another interesting tidbit about engine oils: Higher viz can retain heat, plus adding ‘work’ for the motor. Article went on to question the necessity of heavy-weight racing oils. While my motor has been tricked up including .60 bore, I found no reason with the build to run the 20/50 oil. (Certain builds do call for it.) Was just a thing I thought was a good idea to try; but ultra-thick oil was described for racing; not so much for street driving. I noted that my oil pressure was always super-high even driving it 50 miles on a hot day. Needle barely moved at idle. While my motor needs hi-zinc, reduced the viz to 10/30 finding the pressure acting like it should. Well, along the chain of things I did obtaining the desired result, before I was thinking new/bigger rad.