Coolant leak -
  • 1 Post By cJAY904
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post #1 of 8 Old 09-26-2017, 08:41 AM Thread Starter
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Coolant leak

03 CJ. 4.0 is leaking coolant around thermostat housing. Replaced the gasket 3 times and still leaked. Finally replaced the housing. Still leaking. Hoses and temp sensor inlet are not leaking. Seems to be coming from the housing. I'm out of ideas. Anyone know what may be causing this?

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post #2 of 8 Old 09-26-2017, 09:10 AM
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1984 CJ7 
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Dumb questions:
1) Are you sure you cleaned the area? Did you use a wire wheel on a drill?
2) Did you use RTV? I coated the gasket, bot side with RTV, then hand-tight over night, next day I torqued to specs.
3) New gasket, correct?
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post #3 of 8 Old 09-26-2017, 09:26 AM
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HI did you clean out the groove good that the thermostat sets into? Thermostat goes in the groove then the gasket over that to seal the thermostat in..
good luck
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post #4 of 8 Old 09-26-2017, 10:22 AM
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Time to get out the flat bastard and knock down any high spots that may be on the block where the housing mounts.

80 CJ-5, 74 CJ-6, 56 CJ-5
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post #5 of 8 Old 09-26-2017, 10:29 AM Thread Starter
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Yep. Cleaned until shiny and smooth. New gasket with RTV on both sides. But I did cinch it down and refill immediately after. Will redo and hand tighten, let her sit overnight and then refill. Hopefully that will work. Thanks!
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post #6 of 8 Old 09-26-2017, 01:48 PM
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Did you use thread sealer on the bolts? Coolant will seep out otherwise. BTDT

Have'n you along, is like loose'n 2 good men
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post #7 of 8 Old 09-28-2017, 09:14 AM
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1983 CJ7 
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03 CJ 4.0? What kind of Jeep is it?

Anyway... when you take it off again and clean the gasket surfaces up, put it on a piece of glass and make sure it's flat. They are pretty soft and easily bent if you tighten the bolts too much. If that's the case, grab a new one, do the same with the glass and then take some fine sandpaper using the glass as a backer and rub the housing against the sandpaper/glass until it's really flat. Don't go too aggressive though.

And then as the others said, use a new gasket, coat both sides with RTV, don't forget to install the thermostat, tighten bolts back and forth evenly until snug, let sit overnight, torque bolts back and forth until 13 ft-lbs, fill with water and check for leaks.
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post #8 of 8 Old 09-28-2017, 04:20 PM
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When you apply the RTV, use only a finger film on both sides. Don't over apply because that can and will cause issues.
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