robert99ranger

Grandparents have an 05 Civic Ex. It has lost 10 mpg and doesn't have heat at idle. Coolant is full. No signs of any leaks. No check engine light. Any thoughts? I have read everything from thermostat to head gasket. Temp gauge shows that the car gets up to temperature.

ezone

No heat at idle, but has heat when you rev the engine up.....heater core has an air lock in it.
Usual cause is low coolant, then the system needing 'burped' after refilling.
Then you find out it got that way because of the blown head gasket.

You say the radiator is full? It needs to be completely full to the top of the neck after burping the system, and then the reservoir should be filled to the full line, about the middle of the bottle. The system is designed to keep the radiator completely full under all conditions (when it is working correctly).

There is a water valve in the heater hoses that is actuated by a cable, the lever on top of the valve should move about 90 degrees as the control is cycled from cold to hot. If it moves that far that part of the system is working.


Burping the system......I attach a funnel-fill to the top of the radiator, fill it half full, run the engine, raise the front of the car as high in the air as safely possible to help move air bubbles toward the radiator to escape (sometimes have to rev it up quite a bit so the water pump can help push the trapped air through).

Winter fuel blends and cold weather can really hurt gas mileage, even when a car is running perfect.
Check the air in the tires, pressure drops when it gets cold out.
Check engine light on?

robert99ranger

Just took a drive in it. No check engine light. Heater will roast you out going down the road. Checked the heater control valve before we left and it moves like it should. You can feel it get colder if you sit for a short period but still warm. You can see the temp gauge drop some. After the drive, popped the hood and the upper radiator hose was hot and the bottom was cold.

ezone

IMO this is still describing air trapped in the heater system.

If it is cool out and the radiator is doing its job, this may be normal.
If you let it sit and run a while (heater off, and out of the wind) the radiator may heat up enough to pass warm liquid through the bottom hose.

sdaidoji

iTrader: (1)

repeating ezone question (still unanswered) - did you open the radiator cap to see if there's coolant there to the top?

I know it's a hard job. NOT!

robert99ranger

The answer is in my original post.

robert99ranger

Does that help?

ezone

Damn, I thought you came up with a fix.

robert99ranger

Going to replace the thermostat since that is cheap and easy then go from there. The car has 109,000 with the original timing belt so need to swap that out and might as well do the water pump while I am at it. Going to do a hydrocarbon test on the coolant to see if it is the head gasket.