Leak From Coolant Reservoir Plug

[iSteeve]

For some time I've been noticing a leak from coolant reservoir of my '05 Mustang GT. I think it should be the plug of the reservoir, because the leak happens only with hot engine. May the plug don't manage the high pressure values when the engine runs hot? Any help?

 

[Johnoto]

this is a pretty common problem with the s197s, the thermostat housing is a POS its best to replace it with a sturdier one.

 

[iSteeve]

Thanks a lot for your help