1998 Volvo S70 S70

TIMMIE181

MEMBER
1998 VOLVO S70
5 CYL
FWD
AUTOMATIC

I have a 1998 s70 Volvo an it is over heating. I took out the thermostat because it was stuck so there is no thermostat at all in it. Then I replaced the water pump an its still over heating and drinking all the water I put in it and some one said I must have a leak some weres an I can find one so I bought a bottle of bars leak sealer and put in the radiator just in case. An now the car is still over heating but its not drinking all the antifreeze anymore so why is it still over heating do I need to flush out the radiator again after I put the bars leak sealer in and the car can only be running for about 10 minutes before running hot.

1 Reply

CARADIODOC

MECHANIC
33,873 POSTS

If you're losing coolant and can't find any external leak, the most likely suspect is a leaking cylinder head gasket. That will also prevent the thermostat from opening. Combustion gases can pool under the thermostat. Thermostats open in response to hot liquid, not hot air. Your mechanic can perform a chemical test at the radiator to check for a leaking head gasket. It only takes a few minutes.

Also, two things can cause the engine to overheat when the thermostat is removed. If enough combustion gases get into the cooling system, the coolant won't circulate through the radiator. The water pump is not a positive displacement pump. It simply nudges the coolant along. It can't push it up high enough when there's air in the system. The second possible cause is the hot coolant circulates too rapidly and doesn't stay in the radiator long enough to give up its heat. Even an engine with no other problems can overheat when the thermostat is removed.