O-ring on upper thermostat housing
I need to replace the thermostat on my 2009 4.0 SOHC. I removed the old thermostat and was surprised to see that there wasn't an o-ring or gasket. When I bought the new thermostat I did get an o-ring but now I'm wondering if I need one. The package on the o-ring said 97-00 which I took as years. I put the new one in there without the o-ring and of course it leaked. The question is do I need a gasket, liquid gasket or the o-ring.
Thanks for any help.