Cold Curves
January 16, 2009 8:18 AM   Subscribe

The heater in my 95 G20 is suddenly working intermittently. For the last three days, I get cold air through the vents for the first 20 minutes of highway driving, followed by the heat suddenly kicking in. Then, when I corner around a sharp right hand turn, the air suddenly goes cold, and then heat resumes when I straighten up. Ideas before I head to the mechanic?
posted by blue_wardrobe to Travel & Transportation (6 answers total)
My guess: Your coolant is partially frozen. (I'm assuming you're experiencing extreme cold weather based on your tags.) If your coolant freezes, it won't be able to remove heat from the engine and deliver it to your radiator and/or your heater core. It is also possible for your engine to overheat if the coolant stays frozen. Make sure you have a good mixture of 50/50 antifreeze and water in your cooling system.
posted by knave at 8:42 AM on January 16, 2009

A faulty thermostat might also cause those symptoms. Not sure about a Lexus, but in every car I've owned the thermostat was an easy DIY job or a cheap (1 hour of labor plus the parts) fix at a mechanic.
posted by COD at 9:38 AM on January 16, 2009

air mix flap in the HVAC assembly has a loose actuator or a broken arm.

when you turn it flops over and lets hot air through.

does the temp gauge move in the first 20 minutes? if it comes up like it normally does, it's probs not the thermostat.
posted by KenManiac at 10:01 AM on January 16, 2009

nthing knave about checking coolant.

I have similar problems when my antifreeze is low or empty.
posted by bradly at 10:02 AM on January 16, 2009

Thanks all.

@KenManiac: the temp came up just like normal.

@Knave: a further clue was that the heat came much faster this evening after leaving work, as the car had been garaged all day, whereas at home it's outside in the frigidity of our cold weather.

I picked up some 50/50 coolant, and basically the car took almost the whole gallon, both into the radiator and expansion tank. I'm obviously concerned I have a leak, so I'll be checking regularly and carrying around plenty of spare. I will see if it's losing any over the next day or so.
posted by blue_wardrobe at 6:29 PM on January 16, 2009

Oh, and after the top up, the heater sprung right into action, almost immediately, as normal! Thanks again!
posted by blue_wardrobe at 6:32 PM on January 16, 2009

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