Thermostat

[Doug&Deb]

Just curious about this. My Coronet has a 180 degree thermostat and normally runs between 190-200 degrees. No overheating issues. I’ve had people tell me to run a 160 degree. I understand that it opens sooner but will it change the operating temperature of the engine? I’m not planning on changing anything just curious.

[Sniper]

Thermostats only regulate the low end of the engine's operating temp.

 

It will not affect the upper limit other than to possibly increase the time it takes to get there.

 

there is no reasonable reason to run a 160 degree thermostat on a well running street engine.

 

https://help.summitracing.com/app/answers/detail/a_id/5284/~/should-i-run-a-colder-thermostat%3F

 

[Doug&Deb]

I agree. I always hear people saying to run a cooler thermostat in the summer. I’m okay with a hot engine. I’ve put over 6000 miles on my rebuild in all kinds of weather and no overheating issues. I just wondered about the validity of the idea.

[Sniper]

Comes from the same thinking that gave us nitrogen in tires.

 

Racers do it therefore I must do it.

 

Without considering why racers do it and what their perceived benefit is.

[soth122003]

While the service manual doesn't say to use one or the other specifically, pg 69 in the plymouth manual tells about the uses of each. The first paragraph gives the impression that 160 is the norm and the 180 is for colder climates to help with the heaters.

 

Joe Lee 

[keithb7]

A thermostat is a valve. It opens and closes automatically. Either allowing coolant to flow from the block to and through the rad. Or not. 
 

A cold engine runs inefficient and makes more sludge in the crankcase. Rough running too.  The sooner everything gets hot,(operating temperature) the better. When the engine is cold the thermostat stays closed, so the block coolant cannot circulate through the radiator. This allows the  block to get hot quickly. 

When the coolant temperature  reaches the thermostat rated temperature, it begins to open.  
 

The 160 thermostat opens sooner than the 180. Then the rad takes over and does its job cooling everything as much as it can (within its limitations). If its 100F outside either thermostat stays wide open. The rad cools as best it can. At this point it makes no difference what temperature rated  thermostat you have. Both thermostats are wide open and trying the cool everything down. 
 

However when  its cold outside, maybe the cold air flowing across the rad is cooling the block down too much. We get little heat from the car heater. The engine is not hot enough. Its not burning efficiently again. The 160 thermostat will close and remain closed. Allowing the block to run upto to 160F. Then the thermostat will open, allowing coolant flow to the rad, cooling again. The block cools down. It may get too cool, the ‘stat shuts off flow again. The cycle repeats over and over as the thermostat tries to maintain 160F coolant temperature. The thermostat could also be named a regulator, as this is exactly what it’s doing. 
 

Indeed a 180F thermostat may be better in the winter. If its quite cold out. Keeping the block and coolant a little warmer. Trying to maintain 180.  You may be cozier in the cab. The car enjoys better, cleaner engine fuel burn efficiency.  If you are cruising along, 50 mph on a flat section of road, it’s -20F  outside. The engine is not working hard. Its not making much heat. The thermostat may be closed. A 200F rated ‘stat if possible, might seem a better choice.  The rushing cold air, you still may not get enough heat in the cab. The block just can’t get hot enough.  Then we try blocking the rad with a piece of cardboard. That helps! 
 

Removing a thermostat for better cooling? Many did it back in the day. They did not understand the principles of operation. Old wives tales. Back in the day before social media. You are actually causing premature wear on engine parts by removing a thermostat. The engine takes longer to warm up. 

Edited July 31, 2021 by keithb7

[Doug&Deb]

Interesting. My service manual calls for the thermostat to open at 157-162 degrees and be fully open at 183. So is it a 160 or 180?

[RobertKB]

I believe that is a 160. I think the thermostat rating is when it will start opening. Someone correct me if I'm wrong.

 

Edited July 31, 2021 by RobertKB

[Sniper]

The start to open temp is usually where the thermostat is labeled.  So 160.  But remember, thermodynamics and the understanding of how engines operate has increased tremendously since our cars were built.  Today;s engines can last over 150k miles with simple maintenance.  Ours were lucky to hit 100k, usually much less.  A lot of it had to do with machining processes, material choices and lubricant improvements.  But don't forget moisture in the oil is harmful no matter when the engine was built.  All that sludge found in old engines?  Too cool thermostats helped put it there.

 

Lots of SAE papers on this issue out there.

[Eneto-55]

1 hour ago, Sniper said:

The start to open temp is usually where the thermostat is labeled.  So 160.  But remember, thermodynamics and the understanding of how engines operate has increased tremendously since our cars were built.  Today;s engines can last over 150k miles with simple maintenance.  Ours were lucky to hit 100k, usually much less.  A lot of it had to do with machining processes, material choices and lubricant improvements.  But don't forget moisture in the oil is harmful no matter when the engine was built.  All that sludge found in old engines?  Too cool thermostats helped put it there.

 

Lots of SAE papers on this issue out there.

I'm pretty sure that every car my Dad had passed the 100,000 mark - rolled over, as we said.  I think that lower ending mileage had a great deal to do with how much driving was done annually.  The 53 DeSoto was up to about 115,000, I think, but it was also 18 years old when it was "put out to pasture".  Their next family car was passed on to me, and if I hadn't done some stupid stuff (like going air-borne) it would have gotten farther than it's final 112,000 or 115,000 or so.  And it was 16 years old.  My 46 Plymouth had over 91,000 on it when I bought it in 1980, and it was apparently driven until up into the middle 70's.

 

There was some sales stunt that an auto manufacturer (Chrysler, as I recall) pulled back in maybe the 50's, when they drove a car back & forth across the US, stopping only to fuel up, change drivers, and do oil changes, and put 100,000 miles on it in short order.  Then they tore the engine down to show that there was very little wear.  Judging by the safety inspection records I found in the glove box of my 2010 Dodge Caravan, 50,000 of its 109,000 miles at the time I bought it were put on in one single year.  Our 2009 Dodge Journey has that "change Oil" notice that pops up.  Very soon after an oil change on ours, because it's mostly driven on short trips.  (It only has just over 100,000 on it now.)  I've read someplace that the reason that the change oil notice come up so quickly is that the algorithm (had to look up that word to get the spelling right.  Does that have anything to do with Al Gore?!? ?) counts each start up as an automatic 500 miles.

[Sam Buchanan]

Warning: Thread Drift Ahead

 

In 1956 my dad bought a new Plymouth Savoy with the V8 and overdrive and it was our primary family driver until 1964 when he bought a new Dodge 440 (that's the model, not the engine size). He was careful with regular maintanence and the car wasn't flogged until my brother and I started driving it in the late 70's. Tim and I found out that if you wound out 1st gear you could get the OD to engage and it would take you past 50mph before you needed 2nd gear. ?

 

My family never hesitated to drive the '56 anywhere and it made many long trips to visit distant relatives. It was used as a tow vehicle to drag home dead project VW's and the bumper hitch somehow tolerated hauling a trailer with a couple tons of gravel on it. I don't recall it ever breaking down and the odometer quit with 143K+ miles showing. It was eventually sold about 1980 after the passing of my dad....I've often wondered if it still exists.

 

The '56 was not that far removed from the mechanicals of my '48 P15. I'm developing trust in the P15 that it can offer reliable service similar to what we had in the '56. Those mid-century Mopars were well-designed cars and built out of high quality materials.

[Booger]

Wasnt uncommon to take out a t-stat when you were pouring black pepper down the radiator for "stop leak" I had heard of saw dust but never tried it I tried for years to kill that 54 Plaza sta wa. It delivered US Mail for years 400 stops a day! Doors were welded shut. Crawled in and out of windows like Richard Petty

[John Fleming]

Each of the responses to this topic has provided well thought out information. My experience is with a P15 . I live in the greater Tampa Bay area of Florida. In the run of a year the temp is not below freezing for more than ten days . Temp below mid twenty's most rare. In this area a radiator must be in top condition.  The coolant super clean 50/50 pre mix . A racer stay cool product or water wetter also helps .I prefer a four blade fan and original type bellows 160 thermostat.  On this day the temp is in the 90s in the shade . The feels like temp is in the 100s.