Review on Gates 33963 Thermostat by Ron Chang

Used on 2004 GMC 5.3. I bought it with a new Gates pump and hoses. I used the original water cap and everything fitted perfectly with no leaks. The rubber ring is the seal. No padding material needs to be used. it has a small hole for air to blow through, and the thermostat can balance the water temperature more easily. I've noticed that the thermostat will allow the engine temp to rise to around 180C, then open wide enough to hold it there for a few minutes. From there the flow evens out and my engine runs at a typical temperature of around 200 degrees. So far it has been with single-digit temperatures and 60 degrees weather. It was worth it as branded replacements in a shop were even more expensive from other places.