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Is the OEM thermostat housing really plastic?  I have a '98 Legacy GT wagon and I noticed the housing is plastic.  I couldn't see any part numbers or manufacturer on it so I don't know if it's OEM or not.  The thermostat housings I've seen in videos look like they're made of plastic, too.  Anyway, I noticed that the housing flange and the flange on the waterpump don't meet in the middle when tightened down so that's got me a little concerned.  It seems as though the plastic housing isn't stiff enough.  I've tried a different gasket and still the same thing.  I've used a Six  Start thermostat and gasket and the OEM gasket.  Has anyone else noticed this?

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4 minutes ago, Basket_case said:

Is the OEM thermostat housing really plastic?  I have a '98 Legacy GT wagon and I noticed the housing is plastic.  I couldn't see any part numbers or manufacturer on it so I don't know if it's OEM or not.  The thermostat housings I've seen in videos look like they're made of plastic, too.  Anyway, I noticed that the housing flange and the flange on the waterpump don't meet in the middle when tightened down so that's got me a little concerned.  It seems as though the plastic housing isn't stiff enough.  I've tried a different gasket and still the same thing.  I've used a Six  Start thermostat and gasket and the OEM gasket.  Has anyone else noticed this?

yes they're all plastic.  yes they can seem to not quite sit perfectly like a jigsaw puzzle.  

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48 minutes ago, Basket_case said:

OK.  Thanks.  I guess I'll just try to accept it.  Makes me nervous, though.

100's of thousands like yours have made it 20+ years without issues, take a deep breath. 

occasionally they crack.  if you're worried about it buy a brand new one that has never been overheated, seen road chemicals, UV, or much O2 exposure - they're only $15 or maybe google a metal one. 

https://www.subaruparts.com/oem-parts/subaru-thermostat-housing-11060aa071

Edited by idosubaru
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Thanks for the reassurance. I probably wouldn't have noticed if I hadn't been staring at it before I put the engine back in.  I bled the cooling system without any pressure on it without any leaks.  I was going  to take it on a test drive and didn't want all my efforts go up in smoke (or steam) once the system was hot and pressurized.  After two short trips totaling 15 miles there are no leaks.  I'll still be paranoid until I get more time on it, but I should sleep better now. 

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FWIW there were metal ones on all the 90-94 EJ22 in the first Gen legacies.

I've got about a half dozen of them stashed away.

Come up with a apart # for the 90-94 models and you should still be able to get it from subaru, unless they've completely superseded.

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1 hour ago, FerGloyale said:

FWIW there were metal ones on all the 90-94 EJ22 in the first Gen legacies.

I've got about a half dozen of them stashed away.

Come up with a apart # for the 90-94 models and you should still be able to get it from subaru, unless they've completely superseded.

your hunch might be right, they appeared superceded when i looked, but I've never tried hard.

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