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Discussion Starter · #1 ·
97 2.5 when its 15 degrees out ill let it idle for 15 minutes, it doesn't get all the way up to operating temp until I get in and drive for another 10 minutes, anybody else have issues like that? or if not, anybody know why it takes so long to warm up. my old 89 2.5 didn't take this long to get warmed up. why tj why?
 

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Thats about normal for my I6 here in MI, its a BIG hunk of cast iron to heat up! If I want heat when I warm it up it takes at least 20min at idle. You may want to look into an electric block heater. You plug the jeep into 110 on the cold nights and it keeps the cast iron block warm for fast start/warm ups.

You may also need a new thermostat if its not normal behavior. The thermostat will heat up the block then circulate. If its bad, it will always circulate and take forever to get warm.
 

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My guess is your thermostat is hanging up & letting water circulate through the radiator before it should. I'd install a new conventional (non fail-safe) 195 degree thermostat from Stant or Robertshaw.
 

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Discussion Starter · #5 ·
Jerry Bransford said:
My guess is your thermostat is hanging up & letting water circulate through the radiator before it should. I'd install a new conventional (non fail-safe) 195 degree thermostat from Stant or Robertshaw.
thanks Jerry, do any regular parts stores sell those type? or is it special order kinda stuff. ive got carquest O'Reilly AutoZone and Napa within easy driving access.
 

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Any worthy auto parts store will have a Stant or Robertshaw 195 degree thermostat hanging on one of the aisle displays. Just avoid any thermostat that claims to be fail-safe. Make sure to get a gasket with it, they are sold separately... don't use RTV. And make darned sure both gasket surfaces are absolutely positively 100% clean & no old gasket material is on them which will cause it to leak. Use a wire brush on both surfaces to make sure they are absolutely pristine.
 

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Discussion Starter · #7 ·
oky doky I appreciate it. so my next question is, how long should it take with this new thermostat installed to warm up? bearing in mind its been between 15-20 degrees outside when I go to work.
 

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Discussion Starter · #10 ·
would getting a bra for it help for the mornings its gonna be -15 to -20? ive been told they help but haven't ever tried, if so any good brands to look at preferably less than $100
 

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Your TJ hasn't done anything to deserve the indignity of being forced to wear a bra. :p Slip a piece of cardboard in through the grill slots if need be but a new 195 degree thermostat is the likely cure for the slow to warm engine.
 

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I was just looking at some block heaters on ebay for the 4.0/4.2. Where on the motor do they mount?
 

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I always thought letting a vehicle idle like that wasn't good for it, specifically in cold weather for initial start? And I also always thought the fastest, and proper, way to warm it up was to drive it at a moderate speed?
Assuming of course don't have engine block heater like mentioned by a prior poster.
 

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I let my idle stabilize and then drive slow, its about 2.5 miles with a speed limit of 35mph before hit main road anyway, and before I reach end of that my heat is performing as I expect
 

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tallzdatank said:
why would idling the engine be bad for it. that doesn't make sense.
I was asking a question not posing a statement but a quick Internet search leads to pretty consistent results. Most state that the most effective/fastest way to warm a vehicle is to drive. And several sites, and there is some disagreeable info as well, that bc it's colder and takes longer to warm up some fluids like oil are not efficient which causes unnecessary wear on the motor.
Now many also preface stating 'modern' engines I dunno if the 2.5 or 4.0 qualify as modern. Hence, my question.
 

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with today's engine oil formulations it is not necessary for a a complete warm up before driving provided you keep rpms low until you reach full warm up....sure you can start it and let it idle for a half hour but that likely does more harm than good. from a cold start, 60 seconds of warm up time then moderate driving speed is fine.
 
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