Ok, if your temp overshoots like you stated, that is usually an indication of air in your heads. Might have a leak in the head gasket. This could explain the bubling water if the compression of a cylinder is over pressurizing your radiator. That can push fluid out of the resevoir. To check this, you will need to do a compression check on all 6 cylinders. If you have one or two that are a lot lower than the others, I would suspect a leaking head gasket, or possibly a cracked head. I am going to post the D/O of the cooling system. Maybe something will set off a light in your situation.
Cooling System - Circulates coolant through the engine to remove heat developed by combustion.
Water Pump - Circulates coolant through entire system, block, head, thermostat, radiator, and heater core.
Thermostat - Allows for a rapid engine warm-up and maintains a minimum operating temperature.
NOTE: A normally operating thermostat does not control the upper limit for coolant temperature. The maximum temperature is controlled by the amount of air flow drawn across the radiator.
Cooling Fan - Provides airflow across the radiator to remove heat from the coolant.
Fan Clutch - Controls the upper limit for coolant temperature. The clutch engages to prevent the coolant from reaching its boiling point.
Fan Shroud - Forces air from the cooling fan to be drawn directly across the radiator.
CAUTION: Operation of the engine without the fan shroud significantly reduces the cooling ability of the engine.
Radiator - Transfers heat from the coolant to the air passing across it. The cooling ability of the radiator is directly dependent on the amount of air flowing across it and the amount of coolant flowing though it.
With a cold engine the thermostat is closed, forcing coolant to re-circulate through the engine block and head assembly. This results in a rapid warm up of the coolant.
When the coolant temperature reaches the thermostat set point, the thermostat will begin to open, allowing coolant to flow through the radiator.
NOTE: The upper radiator hose will remain cold until the thermostat begins to open, at this point it will rapidly warm up. This is a quick and easy indication of when the thermostat opens.
With the thermostat open, the cooling system temperature will now be dependent on the amount of air flow across the radiator.
The amount of air flow is dependent upon:
- Driving speed.
- Cooling fan clutch engagement.
Under normal conditions, driving the vehicle in excess of 25 mph will provide enough air flow across the radiator to sufficiently cool the engine.
Under severe conditions, such as climbing a steep hill, the coolant temperature may rise enough to fully engage the fan clutch, thus adding additional air flow across the radiator.
During stop and go driving, the fan clutch will engage to provide sufficient air flow across the radiator.
Monday, August 7th, 2006 AT 8:35 PM