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Unread 11-13-2014, 08:14 PM   #1
Workman13
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1997 XJ Cherokee 
 
Join Date: Oct 2013
Location: Gardner, KS
Posts: 104
Need help. Thermostat gasket won't seal

Ok I decided to change my thermostat today. Took it out and put the gasket on and put it all back together and put some gasket sealant on it. Started adding coolant and it started leaking alot. Took it off and didn't see anything weird with the gasket but I decided to buy another one.Â*
Once again put a little bit of sealant on and let it set for a couple hours. Went to add more and once again its leaking. Does the gasket go on the side against the engine then put the thermostat against that and put back together? Any ideas or advice?

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Unread 11-13-2014, 08:49 PM   #2
AZ Jeff
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Thermostat housing has a depression in it that the flange of the thermostat sits in. The gasket goes OVER the thermostat once it is seated into the recess in the housing.

Do NOT let the thermostat slip out of the recess and get trapped between the t'stat housing flange and the head. If you do, when you tighten the bolts, you will crack the t'stat housing.

Clean the head gasket surface with a single edged razor blade or a SHARP wood chisel.

Clean the t'stat housing surface with a wire brush and, if needed, some sandpaper on a flat surface. Don't gouge the soft aluminum face of the housing.

Use RTV silicone gasket compound on BOTH sides of the paper t'stat gasket.

Don't go crazy on the t'stat housing bolts.

Good luck.
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Unread 11-13-2014, 09:31 PM   #3
sAe23
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It took me two tried (and gaskets) to get it done.
I used a bit of sealant between the t-stat and the engine block to hold it in place while putting the housing in place.
And I used sealant to hold the gasket to the housing, but don't remember using any on the t-stat side of the gasket.
It helps to remove the fan shroud(s), and maybe even loosening the belt to move it out of the way...
Hope the 3rd time is a charm for ya
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Unread 11-13-2014, 10:29 PM   #4
tattman77
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One thing I noticed when I changed mine (92, 4.0 w/aftermarket t-stat housing). if you pull the housing off and place the thermostat in it the way that it sits on the head; rotate the thermostat and you will notice that it will not spin around 360 degrees with out it touching the inside wall of the housing. So if it is not "clocked" correctly it could cause the housing to not pull tightly against the head.
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Unread 11-14-2014, 08:33 AM   #5
SSellers
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I don't use RTV unless the housing or block is pitted and have never had a problem with various ones leaking. Keep in mind different RTV's have different application instructions so check yours. All have to be assembled immediately with some allowing torquing down immediately and others requiring just being tightened finger tight with final torque two hours later. The latter type will actually hinder gasket performance if they are torqued and then subjected to liquid immediately. Most all need at least an hour to skin to avoid wash out and 24 hours to fully cure if you have the time to wait.

Weatherstrip adhesive works good to hold the thermostat to the block so it doesn't slip when installing the housing and gasket. As mentioned regardless if you're going to use sealant clean and degrease both parts (brake cleaner) as good as you can.

The first section of Jeff's instructions "Thermostat housing has a depression in it that the flange of the thermostat sits in. The gasket goes OVER the thermostat once it is seated into the recess in the housing." may be a little confusing because the piece that mounts to the block is called the housing. I'm sure he was just in a hurry like I am most times. The thermostat doesn't go in the housing, it goes in the engine block which has the recess. Then the gasket, then the housing. (on a Ford 302 you put the thermostat in the housing, pain in the rear as it installs vertical like a 4.0L, definitely have to glue it in or use those sticky back gaskets)
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Unread 11-14-2014, 03:07 PM   #6
AZ Jeff
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Quote:
Originally Posted by SSellers View Post

The first section of Jeff's instructions "Thermostat housing has a depression in it that the flange of the thermostat sits in. The gasket goes OVER the thermostat once it is seated into the recess in the housing." may be a little confusing because the piece that mounts to the block is called the housing. I'm sure he was just in a hurry like I am most times. The thermostat doesn't go in the housing, it goes in the engine block which has the recess. Then the gasket, then the housing. (on a Ford 302 you put the thermostat in the housing, pain in the rear as it installs vertical like a 4.0L, definitely have to glue it in or use those sticky back gaskets)
DUH. I happen to own a 302 in an F150, and you are right. I mixed the two of them up! Thanks.
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Unread 11-15-2014, 06:07 AM   #7
SSellers
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Quote:
Originally Posted by AZ Jeff View Post
DUH. I happen to own a 302 in an F150, and you are right. I mixed the two of them up! Thanks.
If it's one of those '85 and up EFI models I hate it for you. I'd rather do the thermostat in twenty 4.0L's then another one of those.
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Unread 11-15-2014, 07:40 AM   #8
skyway0018746
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The 302 has them in the same location. .. my 79 f 100 has it vertical in the front . As well as my 302 with 97 explorer intake .
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