Getting hot on the highway with the AC on.

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RustyRatRod said:
One thing I've done to my 75 F250 and the Valiant is use a high flow thermostat. It makes a big difference. So much so with the Valiant that the cooler 160 high flow thermostat helped knock a detonation issue I was having. I know some of the purists will cringe about a 160 thermostat but it made a big difference. Get the Stewart high-flow thermostat and get the 160. The theory behind it is, it will open long before the engine tries to see heat soak and keep it from ever trying to get there. It worked for me, naysayers be damned.
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after you and YR recommending them I've tried the Stewart thermostat out and I'm having no cooling issues even at 90 degree days with no shroud(will fix that soon), if the OP hasn't tried them I recommend he does next time he does a coolant system service. i got a 195 one since i like my engines to run a little bit hotter, and it has never gone above even in standstill LA traffic. thank you guys for the advice and help
 
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So, I know this cooling thing brings up some pretty heated debate for whatever reason so I will share what appears to be a fix for me. What I found to work was increased coolant flow and a lower thermostat setpoint.
The only change I made was going from a standard parts store 185° thermostat to a high flow 160° thermostat and it now goes no higher than 160 ever. I retraced the route from the trip I took that prompted the original post and instead of hitting over 200°, it stayed at 160°.
160 gives me peace of mind. Maybe 200-210 is an acceptable range, I'm not here to argue that but I drive my car for fun and relaxation and staring at the temp gauge sitting that high is not relaxing to me.
Thanks all for your input on this post!

Cley
20210619_090137.jpg
 
89on35s said:
So, I know this cooling thing brings up some pretty heated debate for whatever reason so I will share what appears to be a fix for me. What I found to work was increased coolant flow and a lower thermostat setpoint.
The only change I made was going from a standard parts store 185° thermostat to a high flow 160° thermostat and it now goes no higher than 160 ever. I retraced the route from the trip I took that prompted the original post and instead of hitting over 200°, it stayed at 160°.
160 gives me peace of mind. Maybe 200-210 is an acceptable range, I'm not here to argue that but I drive my car for fun and relaxation and staring at the temp gauge sitting that high is not relaxing to me.
Thanks all for your input on this post!

Cley
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The reason for that is because before you were not taking full advantage of your radiator. Now you are. I had to get my head around the 160 as well, as they've been trashed on this forum so much it's pathetic. But I did it and man did it ever make a difference.
 
89on35s said:
So, I know this cooling thing brings up some pretty heated debate for whatever reason so I will share what appears to be a fix for me. What I found to work was increased coolant flow and a lower thermostat setpoint.
The only change I made was going from a standard parts store 185° thermostat to a high flow 160° thermostat and it now goes no higher than 160 ever. I retraced the route from the trip I took that prompted the original post and instead of hitting over 200°, it stayed at 160°.
160 gives me peace of mind. Maybe 200-210 is an acceptable range, I'm not here to argue that but I drive my car for fun and relaxation and staring at the temp gauge sitting that high is not relaxing to me.
Thanks all for your input on this post!

Cley
View attachment 1715754216
Click to expand...


I love that hood scoop.
 
89on35s said:
The patient,
74 Duster
Stock 78 318 with a tiny cam and a 670 Holley on a performer 318/360 intake.
Stock ignition, timing is 20 initial and 32 total.
A-500 OD auto and 4.10 gears.
2500rpm @ 70 mph.
Stock 26" rad that got recored to a 3 core about 3000 miles ago. It's nice and clean!
Underhood AC stuff is from an 80s Dodge truck with an aftermarket cross flow condenser about the same size as the rad.
In car AC stuff is Stock 74 Duster.
It holds steady on 180 which is the thermostat rating around town and on the highway with no AC on.
Yesterday it was 90°f outside and I was taking my son and his buddy to football practice about 30 miles away. By the time I got into city traffic (about 20 mile drive with AC on high) I was tickling the low side of 200°f on the gauge.
I got nervous and shut the AC off after a bit of stop and go in the city with the temp going up to just a hair over 200 on the gauge.
My old 360 (R.I.P.) never got over 180 with all else being the same. Should I even worry about it? I am curious about your opinions on what may be causing this.

Cley
View attachment 1715746405
Click to expand...
It may be worth looking at
89on35s said:
The patient,
74 Duster
Stock 78 318 with a tiny cam and a 670 Holley on a performer 318/360 intake.
Stock ignition, timing is 20 initial and 32 total.
A-500 OD auto and 4.10 gears.
2500rpm @ 70 mph.
Stock 26" rad that got recored to a 3 core about 3000 miles ago. It's nice and clean!
Underhood AC stuff is from an 80s Dodge truck with an aftermarket cross flow condenser about the same size as the rad.
In car AC stuff is Stock 74 Duster.
It holds steady on 180 which is the thermostat rating around town and on the highway with no AC on.
Yesterday it was 90°f outside and I was taking my son and his buddy to football practice about 30 miles away. By the time I got into city traffic (about 20 mile drive with AC on high) I was tickling the low side of 200°f on the gauge.
I got nervous and shut the AC off after a bit of stop and go in the city with the temp going up to just a hair over 200 on the gauge.
My old 360 (R.I.P.) never got over 180 with all else being the same. Should I even worry about it? I am curious about your opinions on what may be causing this.

Cley
View attachment 1715746405
Click to expand...
 
PredaFran said:
that's not how cooling works. water doesn't work like that it will always be picking up and shedding heat through the radiator. you can either circulate it slowly so the water stays longer, which can cause centralized boiling which will create hotspots, or you can make it pass through the radiator more times in the same amount of time, which is what using a bigger water pump does. it's just an old tale like cars liking exhaust backpressure.
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I guess I didn't word that very well, and if you think the time the water spends in the radiator makes no difference, it's very easy to test.

Look at at it this way, the water is moving at a fixed rate because the thermostat is the smallest port the water goes through, that will control the amount of water even at different RPM's. It will change some but it will max out even with higher pressure.

If you had a 20" single core rad, the water moving through it will be X what ever that is, but the water will move pretty fast through the rad.

Now put in a 26" 3 core, now you have more surface area and a lot more cores so the water will move a lot slower and will loose more heat not only because the rad is bigger but the water spends more time in it to shed the heat.

Also I have straight drag pipes on my Harley and with putting a small restrictor in the pipe it runs a lot better, so yea it likes a little backpressure.
 
The way I see it is there is more surface area to transfer heat in the 26" 3 core so it should be able to handle way more flow than a smaller rad.

Cley
 
Good god let’s put it to bed!!! The coolant dissipates heat due to increased surface area, not because it’s slowed down good grief!!.....so now that you went from a single to multiple row and saw reduced temps because of the increase of cooling surface area you can then find ways to move the coolant faster for even better cooling if desired. Does fluid speed affect liquid cooling?
 
I think I'm going to write my PHD thesis on this very subject. I just gotta go back and get my Grade 8 First! LOL!

Cley
 
12many said:
Good god let’s put it to bed!!! The coolant dissipates heat due to increased surface area, not because it’s slowed down good grief!!.....so now that you went from a single to multiple row and saw reduced temps because of the increase of cooling surface area you can then find ways to move the coolant faster for even better cooling if desired. Does fluid speed affect liquid cooling?
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Pseudoscientific poppycock!!! That was classic.
 
One the big issues with the internet is that anyone can be an expert. No credentials required. People present all kinds of things as evidence. Most of the time it is hard to tell who really has facts without some sort of references.
 
Me? I prefer the look of a stock rad. Unless I could not keep it cool with a stock rad, then il look at an aluminum one. I don't care for the look of them. I'm weird that way.

Cley
 
My chit runs cool so na na na boo boo.
 
yellow rose said:
The multi pass radiator is a gimmick. It adds to the time the coolant stays in the block and that is wrong. Keeping the coolant in the radiator longer is just wrong, no matter how many times it’s argued.
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To me it looks like the rad is 1/3rd the size just longer, most high output water pumps are rated 35-55 GPM, do you think you could get 55 gal of water through a 26" rad w/ 1 1/4" hose. It still comes down to the smallest part of the system, to me it looks like the thermostat.
 
brian6pac said:
To me it looks like the rad is 1/3rd the size just longer, most high output water pumps are rated 35-55 GPM, do you think you could get 55 gal of water through a 26" rad w/ 1 1/4" hose. It still comes down to the smallest part of the system, to me it looks like the thermostat.
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Right. The thermostat IS the restriction. So why is leaving the coolant in the block longer a good thing? When you answer that you’ll get it. I’ve typed it out and so have others. The less TIME the coolant spends in the block the less heat it carries to the radiator.

Even in the video you posted the dude admitted that the Delta T is about 20 degrees. If the coolant comes out of the block at 200 is that better than coming out at 180? Answer: no.
 
Some years ago I got sucked into a "triple pass" radiator and the only thing it was good for was triple the stress when idling. I tried every fan/shroud configuration possible and had a high flow thermostat and flowkooler pump. The temp would just creep up at idle until it was time to pull over or get on the freeway. All I changed was the radiator to a champion 26" 3 core (with no fan shroud) and presto problem solved. I will keep my water flowing the same way I like my cars, fast lol, (says the guy who hasn't been to the track in over a decade :D)
 
yellow rose said:
Right. The thermostat IS the restriction. So why is leaving the coolant in the block longer a good thing? When you answer that you’ll get it. I’ve typed it out and so have others. The less TIME the coolant spends in the block the less heat it carries to the radiator.

If that is the case just remove the thermostat and let the water flow.
I would like someone to do that and see what happens and let us know.
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yellow rose said:
Right. The thermostat IS the restriction. So why is leaving the coolant in the block longer a good thing? When you answer that you’ll get it. I’ve typed it out and so have others. The less TIME the coolant spends in the block the less heat it carries to the radiator.

Even in the video you posted the dude admitted that the Delta T is about 20 degrees. If the coolant comes out of the block at 200 is that better than coming out at 180? Answer: no.
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If that is the case just remove the thermostat and let the water flow.

I would like someone to do that and let us know what happens.
 
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