Uggggh..Overheating and back fire Help! - Page 2 -
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Unread 06-12-2013, 07:49 PM   #16
1989 FSJ Wagoneer 
Join Date: Oct 2007
Location: melbourne, florida
Posts: 182
Replace the water pump. What else could it be since you've replaced everything else. Just do it.

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Unread 06-12-2013, 09:15 PM   #17
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Join Date: May 2013
Location: glendale, arizona
Posts: 41
Water pump is not a hard job. I make a template for the bolt location. Out of curiousity, have you checked timing? Where in phx. you located?
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Unread 06-12-2013, 09:55 PM   #18
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1999 WJ 
Join Date: May 2006
Location: Austin, TX
Posts: 1,414
if its heating up that fast then the new stat is bad. Make certain you idle it with the cap off until it warms up all the way then you will see the water flowing across the top of the radiator and as the stat opens it will burp the air up and out. Then you can add more water until topped off and then place the cap on. The fan will only affect cooling under maybe 30mph, beyond that speed it should stay cool on its own from airflow. The water pump impellers on some pumps are pressed on and can slip internally also impeller corrosion will cause them to cavitate and have poor flow. You can test the coolant to see if hot exhaust gas from a bad head gasket or head is leaking into the coolant which will boil the coolant fast. Pull the plugs and check the electrodes they will show if coolant fouled also make certain that someone didn't put the 2 steps hotter heat range plugs in that the 70,s model 360s used. The later 80's 90's used a colder plug and a leaner mixture for emissions reasons the engine will run cooler and less detonation prone. Make certain the catalytic converter isn't blocked and that the exhaust heat riser on the passenger side manifold isn't stuck shut forcing hot exhaust to cross over through the intake 100% of the time. I wired mine open. Next check that the thermal actuators on the air cleaner snorkel are opening for full cold air and not grabbing preheated air off the passenger side manifold.
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Unread 06-12-2013, 11:03 PM   #19
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Location: glendale, arizona
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super98isc covered what I was going to add. Are you going by the factory dash gauge or verified by other means?
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Unread 06-13-2013, 04:15 AM   #20
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1990 FSJ Wagoneer 
Join Date: Apr 2012
Location: Grand Haven Mi, USA
Posts: 1,083
Overheating and backfire points to lean condition.
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Unread 06-13-2013, 07:34 PM   #21
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1982 FSJ Cherokee 
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I would pull the new thermostat and test it in boiling water. I had one go bad and it was stuck 'just a little open'. Idled great, heated up right away on the highway. You could see water flow.

I live in AZ. I have a IR gun and timing light. We should check your timing. What general area do you live in?
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carburetor , heat , overheating , radiator , thermostat
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