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Unread 01-10-2015, 11:56 PM   #1
chakkuchan
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1995 ZJ 
 
Join Date: Jul 2014
Location: South Bend, Indiana
Posts: 10
Winter's here, Jeep has no heat

So I just got my 95' 4.0 running about two weeks ago, when it was 50 degrees for Christmas, now that we are getting negative temps I have been testing out the heat. If I leave the temp setting on max heat, and have the fan on full blast, and thirdly turn the output setting from OFF to whatever position, the Jeep blows hot air, for about 3 seconds, then it cools to about lookwarm. Turn the output to off for 15 seconds and back and bam warm air for a few seconds.

I have a 180 thermostat, and engine temp registers to one click left of the middle on the gauge (don't have infrared thermometer), which runs cooler because of my Flex-fan. Also wondering if it could be the blend doors? Thinking about getting a kit http://www.heatertreater.net/Grand%2...ee%2093-98.htm

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Unread 01-11-2015, 04:26 AM   #2
Cleveland
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1998 ZJ 
 
Join Date: Jan 2014
Location: Sagamore Hills, Ohio
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You're going to need to throw in a 195* thermostat if you want good heat. The 180 is too cold for the 4.0, that is your problem, plain and simple.
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Unread 01-11-2015, 01:19 PM   #3
dan66cj5
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To me, it sounds like your heater core is plugged up. I would do a flush on the heater core only... you know how theres 2 hoses going to the heater core ? Well unhook both of them at the engine or somewhere like that, and hook the garden hose to one end and let the other one flow out.

Another possibly is that this valve on your heater hoses is not working properly.. it shuts off circulation of hot water to the heater core when you turn the AC on. I forgot what its called... but I've always chucked this part, its prone to a leak anyway.

Another possibly is that your coolant system is not properly filled up all the way. Not enough water circulation though the heater core.

I dont know why you have a 180 stat and flex fan.. but optimum engine operating temp for the 4.0 is 210 degrees. Best MPG there and less engine wear and tear.
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Unread 01-11-2015, 02:04 PM   #4
jeeepguy
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Quote:
Originally Posted by dan66cj5;27630985)
I dont know why you have a 180 stat and flex fan.. but optimum engine operating temp for the 4.0 is 210 degrees. Best MPG there and less engine wear and tear.
Because he has been listening to the Jeep "engineers" on here that know better than the ones that originally built the thing.
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Unread 01-11-2015, 02:26 PM   #5
Uniblurb
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Same type discussion going on below and look at the link within the link for checking the blend door and motor.

http://www.jeepforum.com/forum/f13/9...l#post27620345

Agree, you're going to have better heat in the cold weather months in living in Indiana w/a 195* T-stat but sounds like a blend door issue too.

BTW, there aren't any valves in the heater hoses on a ZJ.
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Unread 01-11-2015, 04:06 PM   #6
kg6mov
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Agreed, 180 stats work for the V8 if you're not stock and don't live in the cold. The 4.0 needs to run hot.
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Unread 01-12-2015, 09:59 PM   #7
chakkuchan
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Thanks for the input, picked up a 195 thermostat today and will install later this week and get back after a few cold test drive/warmups
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Unread 01-12-2015, 10:29 PM   #8
bahamit_147
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1994 ZJ 
 
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Location: Red Deer, Alberta
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I'm not sure how accessible the heater core hoses are on these jeeps but I'd definitely recommend flushing it. You would be amazed at what you can have build up in there. The first winter I had my audi I had to do that and I swear there was more algae looking gunk that I had in my aquariums...

I'd also recommend a cooling system flush or two with straight water if you've got a heated garage to park it in and let cool. (I always do two fresh water flushes on my system before fully draining and adding my cooling mix (5%extra coolant cause there will still be plain water trapped)) that way everything is cleaned out and properly mixed. Plus... Only use distilled water in your cooling system to prevent that happening again.
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