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Old 04-18-2008, 09:36 AM
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Cooling system help needed 1986 CJ7

Hey guys,

I have recently replaced every part of the cooling system in my 1986 CJ7. When I first started the jeep I noticed that the stat housing was leaking at the bottom. I tried to tighten it down and it cracked. No big deal I just got one from the local auto parts store. I installed the new one with the paper gasket with a little RTV on both sides. It is leaking from the bottom again. I don't get it. It shouldn't be leaking. I'm new to Jeeps but have replaced lots of stats in old muscle cars that I have with out any issues.

Any light you can shed is greatly appreciated.

Dave

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Old 04-18-2008, 09:56 AM
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Is the intake cracked?
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Old 04-18-2008, 10:38 AM
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re;cooling system help

Did you check to see if the inlet was corroded out of round? Just an idea,I've seen it on 4.0 engines before.
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Old 04-18-2008, 11:44 AM
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No the intake isn't cracked and the motor is the 4.2, 258 not the 4.0. Thanks
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Old 04-19-2008, 12:07 PM
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258 cid jeep

Remove the thermo housing clean the block area where it is to mate, take a flat bastard machine file across the surface and see if when you file across if the surface is flat or true.. If it stripes funny, file it until the lines from filing read true and even across the opening at sealing areas. Forget RTV as a sealant there. If everything is true and correct, a little bit of wheel bearing grease will hold the gasket in place until you get it all assembled.

Buy a new thermo housing, or inspect the old one for warpage, or cracks. To true this up rub it back and forth on a flat cement surface a few times, now turn it over and see if it is scratched evenly across the housing. If so put the puppy back together, its gotta be right!
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Old 04-21-2008, 07:54 AM
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OK I took the stat out and the housing was true I will just score it up a little( I guess lightly with a wire brush) and install the gasket dry. Funny thing though the stat goes into the front of the block sideways and when I removed the upper hose the housing was full of antifreeze. I thought the antifreeze would have drained back into the block. So I am just going to put in a new stat anyway even though the one in there was new.

My question is I've read in many posts how people drill a small hole on the side of the stat to relieve pressure. Does this work and if so how large should the hole be? Thanks for all of your help. I appreciate it.

Dave
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Old 04-21-2008, 08:11 AM
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Use a 3/16" drill, it will vent any air in the system. And give added flow around the stat sensor. TF
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Old 04-21-2008, 12:19 PM
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Why do I forget the RTV. The manual says to use a little. I just want to make sure. Thanks
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Old 04-21-2008, 01:41 PM
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I did an engine swap in a 87 Suburban and a 74 Camaro in the last yr, burban had a cast iron intake and camaro had alum, I put them together dry with new stats and a new gasket, no leak. ooh and I did the radiator and new stat in my converson van and used a new dry gasket. no leak




I think clean & dry w/new gaskets = no leaks
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Old 04-21-2008, 02:50 PM
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RTV makes up for irregularities in the surface, if there is any.... when I do thermostats, I use a light coat of spray tack and the gasket and that's it
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Old 04-21-2008, 07:02 PM
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Gasket

3/16 is the right size hole, sounds good. Any size will do the job. The big boys tell me that if you need to use RTV or other sealants then something is wrong. Clean the thermo housing on a wire brush, but to make it true simply rub the mating surface on a flat cement surface until it is clean and shiny all the way across. Or you can lay a sheet of, lets say, 180 grit sand paper on a flat bench and do the same thing. I'm sure that would be true enough for that job.

I like to set the gasket in a thin coat of grease because most times the intake and the thermo housing are made from dis-similar materials and expand and contract at different rates. After a few warm ups and cool downs, they find a happy medium and then in time the grease warms off.
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