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Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 22907
Experience:  BEng hons Mech engineering, in auto industry 22 years
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My Skoda Octavia 2006 heater blows heat only intermittently,will

Customer Question

My Skoda Octavia 2006 heater blows heat only intermittently,will be hot then suddenly goes alot cooler than it should be,fan works ok,but accoring to my garage who are trying to fix it, when the heater fan is on the engine fan comes on too,they think this is cooling the engine too much,also my fuel economy has dropped by about 10 miles per gallon since this problem,could it be due to cool engine ??temperature gauge reads normal.Please have you any suggestions,they have checked all the obvious things .
Submitted: 4 years ago.
Category: Car
Expert:  Matt replied 4 years ago.

yes too cool an engine will cost you fuel economy so I'd 1st suggest replacing the thermostat

Whilst the thermostat is being replaced you might as well also reverse flush the cooling circuit (remove top hose to rad and use a hosepipe to push water into the engine until you get clear water out of the radiator hose) and top up with 30-50% fresh antifreeze. Also check that the small diameter bleed hoses that run from the top of the radiator and the top of the engine aren't blocked as this allow the air to vent back to the header tank automatically.

If you still have a problem then check that the water pump impeller / turbine isn't spinning on its shaft. You should be able to achieve this by removing the bottom hose from the engine and use a screwdriver or similar to feel for the water pump impeller blades, whilst your assistant turns the engine over by hand.
If you can stop the impeller with slight pressure from the screwdriver the pump needs replacing.