New thermostat now it's leaking... Figured

[GMC5.3]

So I got a question,

Replaced old thermostat with a brand new 180 and installed gasket below pictured in blue.

Now I have a leak around the housing that sits on top of the intake manifold.

I accidentally threw away the old one without noticing but do our 72's require the circular gasket around the thermostat like in this video?
https://m.youtube.com/watch?v=ljo3A3F3ATI

Thanks for all your help
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[GMC5.3]

This is basically what the leak looks like


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[A1971Blazer]

That's the correct gasket......you need to make sure the mounting surface on the neck is flat...........they have a nack for warping, especially if someone over tightened it in the past.

Take it off and clean it really good then lay it on a flat surface or lay a straight edge on it......if it's warped, you can usually flatten it back by rubbing it on coarse grit sandpaper on a nice flat, preferably metal, surface. I have belt sanded them too......
if you can't get it flat, you will need to replace it.... it will still leak.

[GMC5.3]

Damn that's not what I wanted to hear, thankfully those housings are only like 25 bucks. Thanks for the response
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[jmillsUT28]

Had the same problem. My housing was not flat at the bottom. Really frustrating when you just installed a newly painted engine and this happens to you. I had a old housing in my garage and it had a oring like rubber gasket instead of the blue one. Might seal a little better...

[GMC5.3]

Thanks , had to go buy a new housing and new bolts, added some sealant as well just to make sure nothing was gonna leak, no problem yet
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[wannabefastcrf]

I had the same problem once. I used two baskets stacked. Work like a charm after that

[asolde]

Felpro makes a gasket with a seal built into it and Mr Gasket makes one to they are reusable and don't leak. Cost like $10 but it's clean and no RTV needed.

[notsolo]

If you have a flat steel surface, cast iron table saw etc. Lay a 1/2 sheet of 320 sand paper on it and swipe the"flat surface" of the housing across a few times see if its flat....if not....Use a flat file and level it out.

[GMC5.3]

I did check the housing after the leak, all seemed fine but I went ahead and replaced it anyway, for ten dollars it didn't seem like a huge deal
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