2001 Vauxhall Astra

Engine Cooling problem
2001 Vauxhall Astra 6 cyl Two Wheel Drive Manual 83000 miles

why does my astra over heat when I go over 50 mph
if I keep it below 50 mph its fine
also the air vents dont blow out hot air any more
a friend said it could be a blown or cracked head gasket
ive checked the water and there dos'nt seem to be any oil in it
any ideas
April 14, 2008.

Check/replace thermostat check heater core hoses are both getting hot with heater blowing and vehicle at normal operating temp. If not suspect heater core is blocked and flush the core !

Dave H
Feb 24, 2009.