James, The green part on the left is the air pivot switch for the vacuum. I normally tell people to replace it due to the fact it's a mechanical item and 20 years old. It really shouldn't turn. It's not that expensive. It routes the vacuum to the vacuum solenoid as the car heats up to advance the timing. As for the sensors on the right side. I would take them out and clean up the brass ends that are exposed to the water. They normally work OK and by cleaning will help regain some of the sensitivity of the thermistor inside. John Hervey www.specialTauto.com << In the course of replacing my Water pump, cleaning that awful area down in there, replacing fuel injectors, and doing a quick tune-up-- I'm also (of course) replacing all my vacuum hoses. Should the green part of the vacuum switch (on the internal water pipe) rotate freely of the brass nut portion? It does on mine. Worth replacing either way? How about the rest of the switch/sensors down in there? I'll never be down that far again... so.... Other than that one bolt the water pump project went (is going) smoothly, if a bit cold out there in the garage. Thanks for your help! James LaLonde 4009 >>