2001 Chevy Impala Gunk in Reservoir

Hi there,

Thank you for the donation,

If the coolant has not been changed for some time you can get a scum building up in the system, this will float on the water and will collect around the highest point, this being the filler so you tend to notice it more, if you have no overheating issues I would just give the system a good flush out have the radiator cleaned change the thermostat and replace the coolant, start here.

Mark (mhpautos)