i plan on doing my water pump and the hoses under the manifold but i have some questions about some of the parts involved. there is a coolant Y pipe 102147 under the intake manifold that has these parts in it 102478 lambda sensor and 102405 therm vac switch. since i will be in this area how do i know if these two parts are bad (102478 and 102405)? what do they do? should i replace them? also the thermotime switch 102125 what does it do? should i also replace this too? thank you mark VIN# 6683