Might want to add what car you are talking about.
I've been having issues with my cooling system. Couple month's back, my heater core blew, so I bypassed it. Coolant was leaking out of my water pump seep hole, so I replaced that as well with a refurbished pump. Car has been having some overheating issues, so I thought it could be the thermostat. However, having replaced the thermostat, housing, crack pipe (damn nipple broke off): the thermostat isn't opening. Replaced the thermostat I bought, with a Stant; hoping it would open fine.
Thermostat still isn't opening; top radiator hose is getting hot, cool bottom hose. Don't think the head gasket is going (or sure hope it's not). I replaced the coolant temp sensor, and it seems to lag getting up to temp; i replaced the CTS month's before the heater core blew.
Maybe it could be that the CTS is faulty? Refurbished water pump could be out? Need an OEM thermostat? I'm running out of ideas. BTW fans are working fine.
Well I woud get an OEM Thermo. I don't know much about the VR6 so maybe I should not chime in. I have a 2.0 and from what I understand if you know the water pump is good and it is not heating up quickly, I would think that it would be a thermostat issue or air in the system. All I know is that the hardest part on doing the cooling system on a 2.0 is getting the coolant back in and the air out.
Edit: You also mentioned that the bottom hose is cool.
I'm going to pick up an oem thermo, put that in and hopefully it will open it. It could be user error honestly, I'm not entirely sure the best way how to burp the system. I've tried massaging the coolant hoses, running the car with the overflow tank open, adding extra coolant...Any thoughts? I know there is a bleeder on the crack pipe but you can't get to it...Could the auxillary water pump not functioning mimic similar problems?