Mercedes 2000 ml 320. I changed radiator and water pump now car only runs half as worm than it used to. So now heat blows cold to little warm depending on how cold out side
If there is an air pocket in the system you will not get hot heat from the climate control system. If the heater worked OK before you replaced the water pump it's probably a stubborn air pocket. You need to raise the front of the car a good 12 and then rune the motor for 20 minutes with the radiator and reservoir caps removed. Have the climate control set to the hottest setting with the blower turned off or on low speed. Top up the coolant as the air bubbles purge. The heat coming out of the vents should be hot at idle, if it only gets hot when you rev the motor you still have an air pocket. Then try revving the motor up and down to 2,500 rpm and squeeze the upper radiator hose at the same time to get the air pocket to purge. If you can't get the air out you will need an expensive Airlift vacuum fill tool for the cooling system. Some vehicles such as Infiniti's will not purge the air with out using the Aitlift brand fill tool.
Definitely check your thermostat out...
I don't mean to be a cheak but did you put all the pipes back where they should be and did you put the thermostat back in?
flush out the heater core and change the thermostat !
