Low temp thermostat - Cherokee SRT8 Forum
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post #1 of 4 (permalink) Old 03-18-2006, 12:49 AM Thread Starter
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Low temp thermostat

Well I just installed the Napa 191 thermostat (180deg version). The engine coolant temps are now:

(During a 55deg day)
at idle or very slow driving under 5mph: 210-215deg
driving around town 20-50mph: 190-205
driving at 70-80mph: 185-200

(During a 49-50deg night)
at idle or very slow driving under 5mph: (210-215deg)
driving around town 20-50mph: 190-200deg
driving at 70-9mph: 190-195deg

For reference here is what a stock 203deg thermostat runs at:
(During a 55deg day)
at idle or very slow driving under 5mph: 210-225deg
driving around towm 20-50mph: 210-220deg
driving at 70-80mph: 210-215deg

The only thing that seems weird is that the bottom line on the coolant gauge is 185deg, which is the normal operating temp of most cars/trucks. It is sort of strange looking at the temp gauge and seeing the needle stay slightly above the lowest line (185deg). Also it is amazing how driving effects the temp on the motor. I assume that it is not only the air hitting the radiator which helps, but also the fact that the water pump is belt driven, so the faster you drive (more rpms), the faster the water pump will spin, giving you cooler operating temps.

I also notice that the truck is a lot more responsive like this. Obviously since the motor now runs cooler, it feels very similar to how responsive the truck is when it is cold in the morning.

I might consider going with a 190deg thermostat to make the temps run slightly higher on the hwy since that is where I do most of my driving. However, I also sure once the air temps warm up to 65-85deg (anytime now), the 180deg thermostat will work perfect.

Oh yeah the thermostat only costs $5.50-7.95 plus tax from Napa autoparts. I also did not drain the coolant. I just spilled some of it while swapping the thermostats and topped the system off with purified osmosis drinking water.

Update:

After more research and testing, I feel that a 190deg thermostat is the way to go. Seeing that the stock 203deg thermostat opperates between 210-225deg and a 180deg thermostat opperates in the range of 190-205deg, a 190deg thermostat should opperate in the range of 200-215deg. I feel this opperating temp is more ideal since the 180deg unit seems to run too cold during highway driving (bairly 190deg). Additionally a 190deg thermostat should allow the computer to run on a opperating temp that is closer to the factory setting while not running too hot (stock= 210-220deg) on the highway.
The 190deg thermostat can be found at Napa autoparts and the part number is: 381-190

If you guys have any questions, let me know. Hopefully the 190deg unit will be the perfect setup.
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post #2 of 4 (permalink) Old 03-18-2006, 12:10 PM
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Re: Low temp thermostat

Great research! Thanks for the info.

2006 Black Grand Cherokee SRT-8
- DUB Air Intake, Corsa exhaust, S/W 1 7/8 off-road headers, B&G Tune installed
2005 Black Sapphire Metallic Volvo S60 R
- Evolve exhaust, Bell intercooler
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post #3 of 4 (permalink) Old 03-18-2006, 09:11 PM
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Re: Low temp thermostat

Thanks for the part #. I will pick one up tomorrow and install it.
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post #4 of 4 (permalink) Old 02-26-2009, 02:11 AM
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Quote:
Originally Posted by Rboosted717 View Post
Well I just installed the Napa 191 thermostat (180deg version). The engine coolant temps are now:

(During a 55deg day)
at idle or very slow driving under 5mph: 210-215deg
driving around town 20-50mph: 190-205
driving at 70-80mph: 185-200

(During a 49-50deg night)
at idle or very slow driving under 5mph: (210-215deg)
driving around town 20-50mph: 190-200deg
driving at 70-9mph: 190-195deg

For reference here is what a stock 203deg thermostat runs at:
(During a 55deg day)
at idle or very slow driving under 5mph: 210-225deg
driving around towm 20-50mph: 210-220deg
driving at 70-80mph: 210-215deg

The only thing that seems weird is that the bottom line on the coolant gauge is 185deg, which is the normal operating temp of most cars/trucks. It is sort of strange looking at the temp gauge and seeing the needle stay slightly above the lowest line (185deg). Also it is amazing how driving effects the temp on the motor. I assume that it is not only the air hitting the radiator which helps, but also the fact that the water pump is belt driven, so the faster you drive (more rpms), the faster the water pump will spin, giving you cooler operating temps.

I also notice that the truck is a lot more responsive like this. Obviously since the motor now runs cooler, it feels very similar to how responsive the truck is when it is cold in the morning.

I might consider going with a 190deg thermostat to make the temps run slightly higher on the hwy since that is where I do most of my driving. However, I also sure once the air temps warm up to 65-85deg (anytime now), the 180deg thermostat will work perfect.

Oh yeah the thermostat only costs $5.50-7.95 plus tax from Napa autoparts. I also did not drain the coolant. I just spilled some of it while swapping the thermostats and topped the system off with purified osmosis drinking water.

Update:

After more research and testing, I feel that a 190deg thermostat is the way to go. Seeing that the stock 203deg thermostat opperates between 210-225deg and a 180deg thermostat opperates in the range of 190-205deg, a 190deg thermostat should opperate in the range of 200-215deg. I feel this opperating temp is more ideal since the 180deg unit seems to run too cold during highway driving (bairly 190deg). Additionally a 190deg thermostat should allow the computer to run on a opperating temp that is closer to the factory setting while not running too hot (stock= 210-220deg) on the highway.
The 190deg thermostat can be found at Napa autoparts and the part number is: 381-190

If you guys have any questions, let me know. Hopefully the 190deg unit will be the perfect setup.
180deg thermostat opperates in the range of 190-205deg, a 190deg thermostat should opperate in the range of 200-215deg?


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