Thermostat Gasket & Housing

[cakummer]

I was just informed by my GM Dealer that I need to replace the Thermostat Gasket and Housing. What does this do and why would it need to be replace. Vehicle is a 2004 GMC Envoy with 87,000km on it, and i just replaced a faulty evap vent valve.

Thanks.

[maxwedge]

Welcome to AF, possible leaks, cracked, what were the symptoms, what is their explanation for the failure, lots of info missing here.

[cakummer]

The only thing they said was of he scan code P0128.

[maxwedge]

That indicates too low a coolant temp reading, usually the t"stat, can't say about a cracked housing.