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post #16 of 20 Old 07-11-2011, 06:55 AM
Foundrydude
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The additional hole is a convenience feature for refilling antifreeze afterward. People are known to drill 1/8" holes in all brands of thermostats if they come out of the box lacking the air bleed hole. But most don't drill and get by fine.

There is nothing special about an OEM jeep/chrysler/fiat thermostat and all brands will work just fine in a jeep. Some of the other brands probably roll out of the same thermostat factory as Jeep therms. It's a commodity type item with more brands than manufacturers.

FWIW I put the cheapest thermostat Oreilly's sells into a nissan V6 yesterday, it had the bypass hole. It's becoming an increasingly common feature in cheap therms, probably because nobody wants to put $2 worth of antifreeze on the ground as the engine burps air while warming up the first time after refill.

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post #17 of 20 Old 07-11-2011, 12:25 PM
SJZ
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Quote:
Originally Posted by tcar View Post
1. Pressure has NOTHING to do with it... as everyone said, it's temperature. Does not matter where the spring is...
You are wrong on several levels.
First off, pressure has everything to do with it, albeit not coolant pressure. The expanding wax exerts PRESSURE inside the sealed thermostat bulb, which causes the 'stat to open, as "jnicewan" correctly stated.
Additionally, if the thermostat is installed with the spring (which is not a bi-metal, as someone mentioned, but merely there to close the thermostat as the wax contracts), up top, the 'stat's bulb will be situated toward the radiator. This may cause overheating, since the bulb will be away from the hot engine coolant... on the wrong side of a closed valve, as it were.
I've been using non OEM thermostats on Chrysler products for many years without a problem.
One thing I recommend doing before installing any thermostat is to place it in a pot of water on the stove to make sure it opens just before the water boils (at sea level), and closes once the heat is removed. You can check a used thermostat this way also.

-Steve
"Those who hammer their guns into plows, will plow for those who do not." -Thomas Jefferson
___________________________________________
'98 ZJ Laredo 5.2 Selec-Trac (249 to 242 swap)
'05 KJ Limited 3.7 Selec-Trac
'94 ZJ Limited 5.2 Q-Trac- sold, after 17 years
'67 International Harvester Scout 800; 345ci V8,T18 4spd, Dana 20 TC
'06 Chrysler 300C SRT8 6.1L
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post #18 of 20 Old 07-11-2011, 12:39 PM
little_Jeep
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Quote:
Originally Posted by SJZ View Post
You are wrong on several levels.
First off, pressure has everything to do with it, albeit not coolant pressure. The expanding wax exerts PRESSURE inside the sealed thermostat bulb, which causes the 'stat to open, as "jnicewan" correctly stated.
Additionally, if the thermostat is installed with the spring (which is not a bi-metal, as someone mentioned, but merely there to close the thermostat as the wax contracts), up top, the 'stat's bulb will be situated toward the radiator. This may cause overheating, since the bulb will be away from the hot engine coolant... on the wrong side of a closed valve, as it were.
I've been using non OEM thermostats on Chrysler products for many years without a problem.
One thing I recommend doing before installing any thermostat is to place it in a pot of water on the stove to make sure it opens just before the water boils (at sea level), and closes once the heat is removed. You can check a used thermostat this way also.
Hold on here........ if pressure is required to open/close the thermostat, then it would stand to reason that a thermostat would NOT open by simply placing it in a pan of hot water on the stove. After all, that pan of water has no pressure, therefore, the thermostat would never open, yet everyone who has done this, will tell you, a properly operational thermostat opens every time. Let water temp cool, and it will close. No pressure involved.
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post #19 of 20 Old 07-11-2011, 12:47 PM
rivalarrival
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Quote:
Originally Posted by little_Jeep View Post
Hold on here........ if pressure is required to open/close the thermostat, then it would stand to reason that a thermostat would NOT open by simply placing it in a pan of hot water on the stove. After all, that pan of water has no pressure, therefore, the thermostat would never open, yet everyone who has done this, will tell you, a properly operational thermostat opens every time. Let water temp cool, and it will close. No pressure involved.
The pressure he is talking about is developed by heating the wax sealed inside the bulb. The wax gets hot, expands, and the increased pressure of the expanding wax pushes the valve open. It's kind of a silly way of looking at it, but it is technically correct.


Along with what everyone else has said, I've never had undesirable results from a generic-branded thermostat, regardless of vehicle.

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post #20 of 20 Old 07-11-2011, 01:47 PM
SJZ
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Quote:
Originally Posted by rivalarrival View Post
It's kind of a silly way of looking at it, but it is technically correct...
Not silly at all, IMO.
I stated quite clearly:"pressure has everything to do with it, albeit not coolant pressure" in response to someone who wrote with authority, "Pressure has NOTHING to do with it", with his emphasis on "NOTHING".
That followed by the absolutely incorrect statement of, "Does not matter where the spring is" , prompted my response.
I'm a little surprised that no one called him on that piece of misinformation, which could potentially cause someone to do harm to their engine.

-Steve
"Those who hammer their guns into plows, will plow for those who do not." -Thomas Jefferson
___________________________________________
'98 ZJ Laredo 5.2 Selec-Trac (249 to 242 swap)
'05 KJ Limited 3.7 Selec-Trac
'94 ZJ Limited 5.2 Q-Trac- sold, after 17 years
'67 International Harvester Scout 800; 345ci V8,T18 4spd, Dana 20 TC
'06 Chrysler 300C SRT8 6.1L
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