Had an E420 come in the other day complaining about low heat... Come to find out the engine wasnt even getting up to opperating temp, thus poor heat.

Thermostat was the fix... But on the E420 the termostat is part of the housing. Best to purchase a new hose also because if it's original it's better to just cut it than risk trying to bend a brittle old hose off and break the housing. It was a no brainer, NEW HOSE.

Best to have a 1/4 inch 10mm universal to get that inside bolt or you're going to have a whole hell of a lot of fun.

Heat has been great every since!