1986 560sl- I have an overheating condition after just refreshing the coolant. I also had the upper hose off to put new clamp on (it goes into the thermostat area). All is back together and it heats up to about 115 degrees when idling. When driving on the highway, it will cool down to about 105 but go back up when idling. At idle, noticed bubbling of coolant in reservoir tank as it has expanded to top of reservoir tank. any ideas? Thanks. rob