The Cooling System...Pushing It's Limitations

[keithb7]

A few more points to chew on:

 

Last evening. About 50F ambient air temps. I flashed up the Plymouth to monitor and note some info. No thermostat in place. 
 

I took the car from my house partway up a big hill. Say about half a mile up. It hit 180F max temp. Turned around. Coasted down the complete hill. Say about 3.5 miles. Maybe about 10 mins going down. No throttle. Great airflow, tranny geared down for holdback. My gauge needle dropped all the way to the starting peg. My gauge shows that as 130F. Water temp could have been lower, needle could not drop lower due to the gauge pin. 
 

Once in the valley bottom I cruised on the flat valley bottom floor. Car maintained 140F at average cruising speed. Say 30-35 mph.  
3rd gear around town. Good air flow due to travel speed. 
 

Then I pointed my car up the hill home and pegged the throttle. Full throttle. No down shifting all the way up. 3rd gear. 4.11 rear end. Stock tires. I’d say 2.5 or so miles up. Decent travel speed at 30-35 mph. I never let up the throttle for about 6 mins or so I’d guess. Decent air flow. Engine coolant temp hit 180F again max.  She was grunting hard and performing well. 
 

I pulled into the drive way, my gauge at 180F. I stopped in front of my garage door. Engine now sitting at idle. Coolant temps immediately began climbing. I let it go, nearing 190F. I then rev’d up the engine a bit to get the fan speed up. I held the RPM’s up. Guessing about 1200 rpm. Immediately the gauge stopped climbing, and then began dropping. The fan was effectively cooling the water.  I brought the gauge quickly back down to 180 and then shut the engine off. I had learned what I wanted. 
 

This tells us plenty. The fan works effectively when it’s 50F ambient. The rad flows well, the water pump works well. Coolant is circulating well throughout the head and block. The rear mounted temp gland immediately reacted to the cooler water temps and the gauge dropped quickly. 
A thermostat does not need to close to allow water to cool.  At least in my example. As I had no thermostat. 
 

I believe my issue is ambient air, combined with a long hard steep climb on a  very hot day. My cooling system as laid out, can only remove so much heat. To get more heat out on really hot days, on that steep hill home, I can:

 

Bigger Capacity, additional core-row radiator

Larger diameter fan

Smaller diameter fan pulley

Enclose fan with a shroud

 

I’ll wager these options will do it. Each one compounding and adding more cooling capacity. All combined, a home run.  

 

Or I just move to a flat area, any flat area where temps can reach 110F. I think she could deal with that on flat land. 
 

 

Edited September 19, 2022 by keithb7

[Adam H P15 D30]

That's hotter than my 49 runs on a 100 degree day, climbing hills with a thermostat.  I would flow test the water pump and radiator...  Mine is bored .040

[Los_Control]

That was a real good test.  Sounds like it was just a few miles/minutes   .... I wonder if you took it out for a afternoon drive without a T-stat, if the water would eventually reach over 180 & continue to climb again?

 

This is where you would need a T-stat to control it. I think it may be possible if you installed a 195 T-stat ... your radiator may be able to maintain a 195 temp all day long.

 

I will be honest here, your radiator just looks puny in the photos.

How tall & wide is the Chrysler radiator compared to the Plymouth?

The depth of the radiator in the photo .... 1.75" thick? .... looks skinny but photo's are deceiving.

The factory honeycomb not very thick either.

 

Here is a photo of the $50 radiator I plan to use in my truck to replace the leaking original. ... it does not leak, painted black will look good enough for me.

The width & height are the same as original ... It is 3.25" thick, so it as least a 2 row .... I dunno about 3 row.

When I install it, it will take up just as much room as the original & not look out of place. ..... I hope it does it's job keeping the engine cool.

 

 

[Sniper]

rising temps at low, or no, road speeds generally is an airflow issue.  My 64 300 would overheat in stop and go traffic.  

 

New water pump, new thermostat, new hoses, bigger junkyard radiator, nothing helped.  Then a bud of mine was at a yard and saw a shroud that would fit the radiator I had, no idea how he spotted it.  That solved the issue as it forced all the air the fan was moving to come thru the radiator. 

[keithb7]

Just put in a 180F stat in my Plym.  
 

I wonder what the symptoms might be if a person installed one upside down?  Asking for a friend.  Lol. 

It is possible I did this. I’ll never know. I took it out a month ago. 
 

She ran up to 180 nicely and stayed there on the down hill and flat roads. Nice to have heat in the cab again tonight. 

 

Edited September 20, 2022 by keithb7

[keithb7]

With the 180F stat in, I just went for a drive. I was at 180 on the gauge at the bottom of the hill. Hit it again hard. Pulled into my driveway  at temp seen in the image. 210F.  Current ambient air temps 62F. 
 

 

Edited September 20, 2022 by keithb7

[andyd]

Keith.........I have just gone thru your posts re the cooling issue and after seeing the pics of the radiator in the Plymouth I agree with Los Control that your radiator appears too small.........do you have any idea what it was originally in?.......have you ever blocked off the lower outlet and filled the radiator with a known quantity of water.....my Oz mopar shop manual states that 1938 Plymouths have 12 Imperial Quarts as the water capacity, but doesn't indicate how much of that is in the radiator.........I would think that 2/3rds of that, ie 8 quarts or 2 gallons would or should be in the radiator, note that this would be for the original 23" long Plymouth engine........your car has the 25" long engine now, same as your 38 Chrysler............which runs cold.......lol.........is there any way to compare the capacity between the radiators in each car or even better still, swap radiators and see what happens.............andyd       

[vintage6t]

37 minutes ago, andyd said:

.....is there any way to compare the capacity between the radiators in each car or even better still, swap radiators and see what happens.............andyd       

It won't give you the absolute capacity but you can measure the physical dimensions (l*h*d) of each core to get the relative difference in the capacity of the two cores in %. 

[Sniper]

10 hours ago, keithb7 said:

I wonder what the symptoms might be if a person installed one upside down?  Asking for a friend.  Lol. 

 

My  came with the thermostat upside down.  It ran cold, I suspect the coolant flow was pushing it open despite the temperature being well below it's opening point.