Pat, I just did what you're doing for a buddy. I think the temp sensor is in the thermostat housing. Check the wire connector. There is several ways to bleed the air from the system. 1. Drill 1/8 th hole in topside of thermostat and pump upper hose after filling rad. [my favorite] 2. Loosen temp sensor at thermostat till water runs out, then tighten. 3. Leave thermostat out while filling rad till water runs out, then install thermostat. Budlight