Car over heats up when I turn on Heater

JIMMY1258

MEMBER
HONDA CIVIC

Hi my Honda Civic 2005 64000 miles Ex model vtec car over heats when I turn on Heater I have taken to Honda Dealer can not find what is causing problem have checked Radiator ok pressure test cyl ok chaged tstat flushed coolant system heater core all ok replace heat switch check for carbons all ok I have driven for three days all seems ok except when I turn on heater fans work checked with gage when motor get too 230 Degrees fan comes on when I run ac all ok if I climb hills car heats up it is lossing some fluid but no one can find any leaks Help

1 Reply

RASMATAZ

MECHANIC
75,992 POSTS

Losing fluid and its not leaking its being burn

Maybe if it goes above 230deg this is where the crack some where opens up and the coolant is being burn in the combustion chamber. Rad Cap seal is it okay-

Try bleeding the cooling system could be air lock see below

Always bleed air from cooling system after replacing coolant. Set heater for maximum heat. Remove radiator cap. Loosen drain plug and remove drain bolt (if equipped) from engine block. Drain coolant reservoir. Fill coolant reservoir to MAX mark with 50/50 water-coolant mixture. Loosen bleed bolt and fill radiator up to base of filler neck. Close bleed bolt when coolant flows out without bubbles. Tighten bleed bolt. With radiator cap removed, start and operate engine to normal operating temperature. Add coolant if necessary and check for leaks.