Rattler

Perhaps keep bleeding the top screw until only coolant comes out? Air hissing usually means it needs to be bled. You also have to bleed the top heater core hose at the firewall next to the battery. The procedure is something like start engine and maintain engine speed of approximately 2000 RPM for approximately 3 minutes. Then allow engine to run at idling speed until lower hose on radiator becomes hot. Then bleed.

Unless the waterpump is bad?

-Brian

lyleswk

Have you done any work to the car or did this just start.

UKAudiMT

Sounds like water pump to me.. Have you checked that your getting coolant flow when you rev the engine?

lyleswk

Assuming he;s done no work, yeah. Thermostat would act a little differently,