Where'd the heat go - JeepForum.com

 
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post #1 of 8 Old 11-15-2013, 07:14 PM Thread Starter
bunk02
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1997 ZJ 
 
Join Date: Nov 2011
Location: Lancaster
Posts: 47
Where'd the heat go

I had a broken vacuum line for 1st 2 winters I owned my 97 Grand Cherokee Laredo ZJ 5.2L (only defrost worked, no vet air or cruise); finally got it fixed over summer. Heat worked great, easily made the cabin into a pizza oven. Then this morning on way to work, no heat only cold air blowing out of the vents; temp outside was in the 30's. Jeep's temp gauge got halfway up by time I got to work but still no heat. Haven't got a chance to look at anything yet, where should I start? I have read an open thermostat, bad heater core, or a bad blend door or blend door motor. What diagnostic steps should I do to eliminate the easiest things 1st?

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post #2 of 8 Old 11-15-2013, 09:41 PM
jabba974
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1996 ZJ 
 
Join Date: Mar 2013
Location: Ionia
Posts: 246
Start by checking the coolant level...Then warm the engine up and check the heater hoses and see if they are both warm/hot or not....Could be a bad t-stat..or plugged heater core...
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post #3 of 8 Old 11-16-2013, 07:39 AM Thread Starter
bunk02
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1997 ZJ 
 
Join Date: Nov 2011
Location: Lancaster
Posts: 47
Went out this morning, warmed truck up for 10 minutes then got in for a little trip around the block. Small puff of warm air then cold.....then after accelerating from a stop sign warm air returned. Temp gauge had been almost to 240. Took it right home and popped hood to find an antifreeze shower had soaked the entire front 1/2 of engine. Needless to say the radiator was empty. Gonna let it dry out a little and see what I can see; obviously sounds like something was plugged
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post #4 of 8 Old 11-16-2013, 09:08 AM Thread Starter
bunk02
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1997 ZJ 
 
Join Date: Nov 2011
Location: Lancaster
Posts: 47
Looking like the water pump took a crap; replace, refill, recheck. Update afterwards
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post #5 of 8 Old 11-16-2013, 09:44 PM
jabba974
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1996 ZJ 
 
Join Date: Mar 2013
Location: Ionia
Posts: 246
Get yourself a coolant pressure tester and see where the leak is coming from(if you can find it already)...
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post #6 of 8 Old 11-20-2013, 07:05 PM Thread Starter
bunk02
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1997 ZJ 
 
Join Date: Nov 2011
Location: Lancaster
Posts: 47
Replaced water pump and the heat has returned, no leaks. However, a new problem has arisen which probably has nothing to do with the previous. Started Jeep up this morning to let it warm up for a few minutes, put it in reverse backed up 15 feet and it stalled. Cranked and cranked and cranked until it finally started but wouldn't keep running unless I was feathering the gas. Managed to get it back in the garage and get to work via other means......so where do I start to diagnose this issue?
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post #7 of 8 Old 11-20-2013, 07:10 PM
JasonStebbins
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1997 ZJ 
 
Join Date: Jan 2009
Posts: 3,138
Sounds like a dying fuel pump to me. But it could be 50 different things. Check fuel pressure first, voltage to the CPS and TPS then wiggle the three harnesses for the PCM while idling.

Check ZeeJays checklist in my signature for more ideas.

Poop
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post #8 of 8 Old 11-20-2013, 07:18 PM
bigbill888
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1996 ZJ 
 
Join Date: Nov 2009
Location: michigan
Posts: 969
My guess: your coolant was diluted (or water) froze on the first cold night, and she overheated in the morning. How am I doing so far?

96 ZJ Laredo, 4.0, 242, 230K
95 ZJ Limited, 4.0, 242, 140K
98 XJ Sport, 4.0, 231, 140K
All work well
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blend door , heater core , no heat , thermostat , zj

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