most likely heater core leaking
This sounds like a common problem with the 3.1L and 3.4L v6 of the lower intake manifold leaking. TechJK ----------------------
look on the lower part of the radiator in one of the corners. If it is easier, pull the lower hose to drain.
The Chevy lumina vans are bad for stab link kits and lower control arm bushings. If you inspect the lower control arm See if the bushing has come free of its bonding. Also does your van have a 3.4 in it. Check to make sure the intake gaskets arn't leaking. Another major problem for this vehicle.
"low coolant? sensor location, NOT "engine temperature" sensor location is of passenger side of radiator tank. remove headlamp assembly for a direct visual on sensor. it is a black plastic square on side of radiator lower than the upper radiator hose inlet. has a two wire connector
A blown head gasket can allow coolant to see into the manifold, and out the exhaust. A broken piston ring can also cause this problem.
You can drain coolant from 2005 Equinox by removing lower radiator hose on passenger side of vehicle. This will not remove all coolant from vehicle but will be adequate for a coolant flush.
The crankshaft sensor is located on the lower part of the engine closest to the firewall, on the passenger side of the car.
Sounds like either the plug or the radiator need replaced.
If it is leaking next to where the lower radiator hose attaches to the engine, the water pump has failed. That hole is the water pump weep hole.
it is behind the glove box on the passenger side. The lower dash panel must be removed to gain access.
Lower passenger side of radiator, motor side.
There are marks on the side of the coolant reservoir that indicates the proper level. Keep it filled at all times if you are losing coolant you may have a leaking hose or may be your Lower intake gasket. you should not ever have to add coolant to your system.