Temp gauge drops when heater is on and foot off gas pedal

168,000 MILES • 4 CYL • FWD • AUTOMATIC
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RIDUNCAN
  • MEMBER
  • 1 POST
I have a 2004 Honda Civic EX Sedan.
I have had my car to the dealership 12 times, and they can't seem to find the problem.
The car will not warm up in the morning. The temperature gauge will not move off of C until I give it gas. The heater blows cold air until I give it gas. When I take off, the temp gauge rises to normal, and the heater starts to blow warm air. Also, when I have the heater on and I go down a long slope (mountain), the temp gauge drops, and the heater blows cold air. After I get over the mountain and give it gas, the temp gauge begins to rise to normal again. The car has never overheated.
The dealership has installed and done the following...
Flushed the a/c and heater core.
Installed upper hose.
Installed new thermostat.
Installed head gasket, and while there, installed timing belt and water pump.
They have also "burped" it every time I had it there.
My car is currently at the dealership, and they have submitted a trouble ticket to the Honda Tech Line.
Please help!!
Sep 19, 2014 at 7:59 AM
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HMAC300
  • ✓Experienced Mechanic
  • 48,601 POSTS
try a new radiator cap it may not be holding pressure causing part of the problem can't think of much else. have them put a pressure tester on it to see if it's holding or not.
Sep 19, 2014 at 8:09 AM
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