High Flow Thermostats

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12,742
Location
Phoenix, AZ
For my Jeep, I need to replace the thermostat housing. I've tried a few different thermostats, not sure I've seen much of a difference. With our extreme heat, it runs a bit warm. While the housing is off, now would be the time I can replace the thermostat. It's currently got a 180* High-Flow Murray (Murray is OEM manufacturer). I also have a 195* OEM Murray (I bought from the dealer) and a 195* High-Flow Murray. So my question is, which do you think would provide better cooling in extreme conditions? The reason I wonder is with a wider opening, this means the coolant might flow faster which would mean less time in the radiator to cool down. But I see it also as maybe being beneficial, less time in the engine getting hot.
 
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96
Location
NW, GB
The faster the flow the better the cooling. The maximum flow will be before the pump cavitates. "less time in the radiator to cool down" is a fallacy. Edit: PS. I am ignoring laminar/turbulent flow considerations.
 
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Messages
21,651
Location
Apple Valley, California
Will not make a bit of difference. Jeeps 4.0's run hot. Especially in an xj. The restriction is the radiator and not the thermostat. Also remember that once a stat is open be it a 160,180 or 195 etc it is no longer regulating the coolant temp. The coolant temp is now at the mercy of the rest of the cooling system.which is too small on you're xj. This was my wrangler friday.

IMG_20200710_172127.jpg
 
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14,319
Location
Central NY
What is "warm"? When my XJ had AC, I was rock crawling in 95 degree heat in the bright sun and never passed 225. That's pretty much ideal for a 4.0! What do you have done to the cooling system? The 4 cylinder fan clutch (caution you NEED good engine and trans mount, otherwise the fan will go through the radiator if you hit something!!!!!), e fan on a toggle switch, napa water pump and always having a good radiator have never let me down. Until the thermostat I had went bad, I never could get it to overheat. That includes being stupid in the mud and having the thing pegging the rev limiter for minutes on end on a hot summer day.
 
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6,217
Location
Connecticut
-Stant Super stat 195* -Hesco high flow thermostat housing -A decent radiator and a clean cooling system will go a long way 240* is not normal unless you are running on the sand dunes at high RPM. A cooler thermostat won't solve an overheating problem, as it only determines the MINIMUM operating temp of the engine.
 
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1,607
Location
USA
Originally Posted by Nick1994
So my question is, which do you think would provide better cooling in extreme conditions? The reason I wonder is with a wider opening, this means the coolant might flow faster which would mean less time in the radiator to cool down. But I see it also as maybe being beneficial, less time in the engine getting hot.
As far as just the thermostat-it will have no significant impact "Hi Flow" is a meaningless term because the pump determines the flow- not the size of the thermostat. To achieve additional cooling (heat exchange) you are going to have to address things such as surface area of the radiator, cleanliness ( loss of efficiency), more air flow to remove heat ( more fan)- then adjust pump to get the required dwell time for maximum transfer. ( you can over pump a heat exchanger and actually reduce heat removal)
 
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4,989
Location
Los Gatos, CA
if other components are operating correctly, if you want to lower coolant temps I would install a better radiator. Either bigger, more efficient or both.
 
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916
Location
Hollister, CA
On my Wrangler that I had the Golen 4.6L stroker engine in, I put in a Hesco high flow thermostat housing and their high flow water pump along with a new factory style radiator. Initially I had the high flow thermostat in, but the temp was too low for my liking so I replaced it with a OEM one. The temps never got above 210F, even in summer temps of 100+F. A couple of caveats is that I did not have AC and I had the manual transmission. The only other thing I did was smooth out the sharp edges inside the high flow thermostat housing where it was machined by Hesco. I miss that Jeep. It was a blast to drive with the stroker engine, 5 speed manual tranny, and 4.10 gears.
 
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24,699
Location
MA, Mittelfranken.de
Originally Posted by ABN_CBT_ENGR
Originally Posted by Nick1994
So my question is, which do you think would provide better cooling in extreme conditions? The reason I wonder is with a wider opening, this means the coolant might flow faster which would mean less time in the radiator to cool down. But I see it also as maybe being beneficial, less time in the engine getting hot.
As far as just the thermostat-it will have no significant impact "Hi Flow" is a meaningless term because the pump determines the flow- not the size of the thermostat. To achieve additional cooling (heat exchange) you are going to have to address things such as surface area of the radiator, cleanliness ( loss of efficiency), more air flow to remove heat ( more fan)- then adjust pump to get the required dwell time for maximum transfer. ( you can over pump a heat exchanger and actually reduce heat removal)
^^^ This. Things like flow rate, thermostat/restictor opening size can be tuned/tweaked to work optimally together.
 

Nick1994

Thread starter
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12,742
Location
Phoenix, AZ
Originally Posted by Miller88
What is "warm"? When my XJ had AC, I was rock crawling in 95 degree heat in the bright sun and never passed 225. That's pretty much ideal for a 4.0! What do you have done to the cooling system? The 4 cylinder fan clutch (caution you NEED good engine and trans mount, otherwise the fan will go through the radiator if you hit something!!!!!), e fan on a toggle switch, napa water pump and always having a good radiator have never let me down. Until the thermostat I had went bad, I never could get it to overheat. That includes being stupid in the mud and having the thing pegging the rev limiter for minutes on end on a hot summer day.
Regular driving, such as sitting at a stoplight, going through a drive thru etc. will get it to around 230. I let it idle for 10 min out front of my house the other week and it was at 233. If I could keep the temp outside to the 90's it wouldn't be so bad. Once it hits triple digits, it can't keep up. I've literally done everything to it. The entire cooling system has been replaced. I had the big fan clutch on it and it didn't help, it robbed too much power so I put a stock one back in.
 
Messages
2,563
Location
Kentucky
I've never seen an appreciable difference in summer running temperature between a 180F and 195F thermostat. I've tried both in a few vehicles, and they always seemed to run 195-205F in summer regardless of which thermostat was used. Now in winter or during warm-up (before the engine heat soaks) it will run at 180F as opposed to 195. But once you're sitting it traffic or doing around town driving, it didn't seem to make a difference. Since discovering this, I've opted not to use a 180F thermostats as it contributed to less efficiency and no real improvement in max temps the engine would see.
 

Nick1994

Thread starter
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12,742
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Phoenix, AZ
This thread wasn't really intended for discussion of lower and higher temp thermostats, but for high flow ones (bigger opening).
 
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568
Location
Pacific Northwest
I've never seen a high flow thermostat cure a hot running condition unless the thermostat it was replacing was defective. I don't think using the high flow stat will hurt except for maybe taking a little longer to warm up -- not an issue in AZ, I'm sure. As for running, "warm," do you have the factory fan shroud installed? Do you have issues at highway speeds or is it just during low speed driving or idling?
 
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12,466
Location
Indiana
Originally Posted by SpitFire6
The faster the flow the better the cooling. The maximum flow will be before the pump cavitates. "less time in the radiator to cool down" is a fallacy. Edit: PS. I am ignoring laminar/turbulent flow considerations.
Slower flow rates will absorb more heat. I'd personally look more into a multi row radiator.
 

Nick1994

Thread starter
Messages
12,742
Location
Phoenix, AZ
Originally Posted by ripcord
As for running, "warm," do you have the factory fan shroud installed? Do you have issues at highway speeds or is it just during low speed driving or idling?
I've made a few posts about it over the years. Desert driving (offroad) really gets the coolant dirty as the overflow bottle is vented. I've been flushing the cooling system since last weekend by pulling the lower hose. This leave a bit still in the engine but I get about roughly 1-1/2 gallons out. I've flushed 8 gallons of distilled water through it so far. I will have it perfectly clear eventually. Have 7 gallons left of distilled water for flushing but will get more if needed. By warm, I mean after draining the radiator and refilling and driving 2 miles to Starbucks and idling for 10 minutes, this is my temp: [Linked Image]
 

Nick1994

Thread starter
Messages
12,742
Location
Phoenix, AZ
Originally Posted by dlundblad
I'd personally look more into a multi row radiator.
Yes I've posted to CherokeeForum for suggestions, will get something good.
 
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1,607
Location
USA
Originally Posted by dlundblad
Slower flow rates will absorb more heat. I'd personally look more into a multi row radiator.
In general terms that's correct but there are many other considerations in a closed circuit heat exchange system. It can absorb "too much" and start a change of state and then you lose a lot of transfer. Also the slower flow rate applies to the transfer of that heat too. That's why heat transfer is a series of ratios founded in the induced heat of the device and the operating temperature range to size it. Just arbitrarily changing parts and changing those ratios can adversely affect thermal transfer.
 
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