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Unread 08-30-2013, 12:33 PM   #1
TrucksBootsNGun
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1988 MJ Comanche 
 
Join Date: Aug 2013
Location: Flagstaff, ARIZONA
Posts: 46
Still Running Hot.....

Ok so I am still running hot in my '88 MJ 4.0L even after I swapped the radiator for the '92 open design (also swapped heater control valve and made an overflow tank). While I was in there I decided to swap out the thermometer for a new 160* one instead of the stock 195*. I also replaced the water pump and I am still running the pure distilled water from when we tested it for leaks. At highway speeds the thermometer says exactly on 160* but when you are wheeling at lower speeds she runs at about 210* never got it much higher because it was a short trail but i feel like its gonna keep going up. I am slightly worried because living in Flagstaff we need antifreeze which means less water. Did I miss anything when I swapped everything over?

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Unread 08-31-2013, 08:56 PM   #2
cruiser54
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1990 MJ Comanche 
 
Join Date: Oct 2009
Location: Prescott, Arizona
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210 is normal. A 195* THERMOSTAT should work fine. 160* is too low. You'll be freezing your *** off in the mornings this winter in Flagstaff. The fan clutch is most likely needing replaced.
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Unread 09-03-2013, 07:24 PM   #3
TrucksBootsNGun
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1988 MJ Comanche 
 
Join Date: Aug 2013
Location: Flagstaff, ARIZONA
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Quote:
Originally Posted by cruiser54 View Post
210 is normal. A 195* THERMOSTAT should work fine. 160* is too low. You'll be freezing your *** off in the mornings this winter in Flagstaff. The fan clutch is most likely needing replaced.
The reason this I went with the 160* is I am from SD just going to college in Flagstaff. That 195* was useless in San Diego stop and go traffic. When you say clutch fan you are not referring to the electric fan that kicks on when the A/C does are you? That fan won't kick on because the A/C compressor is bad (I think its the compressor because when the system was charged and the A/C was on there was freon coming through the vents according to a sniffer do-hicky my dad has. there is a big enough leak that it was completely unpressurized in less than 5 mins) The A/C has this weird fail-safe that if the system is out of freon it wont engage the A/C clutch.
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Unread 09-03-2013, 08:14 PM   #4
cruiser54
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1990 MJ Comanche 
 
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You'll freeze your balls off in flag with a 160 stat this winter.

https://www.google.com/search?q=fan+...w=1680&bih=806
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If you own a Renix Jeep, you'll want to check this out. >

An index to over 25 write-ups can be found in Post #1.

Cruiser's Mostly Renix Tips
Refresh*Connections*Before*Replacing*Components
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Unread 09-08-2013, 06:48 PM   #5
wgirvine
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1992 XJ Cherokee 
 
Join Date: Oct 2007
Location: Rosamond, CA
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Three things:
The thermostat regulates the MINIMUM operating temp of the engine. It does not regulate the MAXIMUM temp. When a 160 degree t-stat is open, it flows the same amount of coolant as a 195 degree t-stat when it's open. The max temp of the engine is controlled by the size and efficiency of the radiator. Forcing an engine to run cooler than it was designed to will cause poor gas mileage. And other problems...

The mechanical fan has a viscous coupling, commonly called a fan clutch. It allows the fan to slip a lot (run slowly) when the air coming thru the radiator is cool. It engages and speeds up the fan when the air coming thru the radiator is hot. Overheating at low speeds (low air flow conditions) such as stop-and-go traffic is usually caused by a bad fan clutch. Replace. They don't last forever, anyway. Make sure you get the one with the funny little flat coil spring in the front.

And the electric fan comes when (1) the AC is turned on, OR (2) when the coolant gets hot... around 215, I think. You need to get that fan fixed also.
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Unread 09-08-2013, 07:31 PM   #6
cruiser54
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1990 MJ Comanche 
 
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Location: Prescott, Arizona
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Quote:
Originally Posted by wgirvine View Post
Three things:
The thermostat regulates the MINIMUM operating temp of the engine. It does not regulate the MAXIMUM temp. When a 160 degree t-stat is open, it flows the same amount of coolant as a 195 degree t-stat when it's open. The max temp of the engine is controlled by the size and efficiency of the radiator. Forcing an engine to run cooler than it was designed to will cause poor gas mileage. And other problems...

The mechanical fan has a viscous coupling, commonly called a fan clutch. It allows the fan to slip a lot (run slowly) when the air coming thru the radiator is cool. It engages and speeds up the fan when the air coming thru the radiator is hot. Overheating at low speeds (low air flow conditions) such as stop-and-go traffic is usually caused by a bad fan clutch. Replace. They don't last forever, anyway. Make sure you get the one with the funny little flat coil spring in the front.

And the electric fan comes when (1) the AC is turned on, OR (2) when the coolant gets hot... around 215, I think. You need to get that fan fixed also.
208* or 218*.
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Quote:
Originally Posted by chris87xj View Post
If you own a Renix Jeep, you'll want to check this out. >

An index to over 25 write-ups can be found in Post #1.

Cruiser's Mostly Renix Tips
Refresh*Connections*Before*Replacing*Components
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Unread 09-13-2013, 04:12 PM   #7
carnuck
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1984 J-Series Truck 
 
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195 or 180 stat, 50% antifreeze, check the waterpump blades (mine were chewed up by the spring from the bottom hose!), loosen the temp sender to burp the head "air bubble" and add a bottle of Water Wetter from Redline (or similar like Purple Ice or Amsoil cooling booster)
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