Q: When I try to run the heater my thermostat gets stuck on C and my car reacts like it is overheating.Sometimes draining the coolant

asked by on November 13, 2017

When I turn on the heat or defrost on my dashboard thermometer gets stuck at the bottom on C. Then the sensors start lighting up telling me my car is overheating. When I check the coolant levels (after the car has been parked for awhile) sometimes it is completely drained, but most of the time there is still coolant in the radiator and the reservoir. This sometimes lasts for several days and then goes back to normal (as long as I don’t turn on the heat) but this time it seems to be stuck.

My car has 200000 miles.
My car has an automatic transmission.

You may have a clogged heater core that may be prohibiting the outer linings of the heater core to get hot. As you know, the heater core is a series of tubes that the coolant runs through that generates the heat from the warm coolant after circulating through the motor. These tubes can occasionally develop a buildup on the inner walls such that when the heater core is "flushed" this buildup on the inner walls of the lines remains and still allows the coolant to flow through the heater core. It is important to note that when the heater core is "flushed" it is possible to get good flow through the heater core while the inside walls of the heater core remain caked with buildup. As a result, the buildup on the inner walls prevents the temperature from rising to its capability due to the insulating effect of this buildup on the inner walls which will prevent the necessary heat transfer to properly heat the inside of the car. I would recommend having an expert from YourMechanic come to your location to diagnose and replace your heater core.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Temperature gauge not reading correctly.

This vehicle has had many electrical issues with bad crimps in the wiring causing gauges to read erratic and when the computers see issues in the wiring it will turn on the light and put the gauge to the low...

Front suspension shaky.

You need to have the front lower control arms checked for worn out bushings and ball joint. The struts may be worn out also. The rear tires should be checked for balance or damage. I recommend having a qualified mechanic,...

Stuttering Nissan

It sounds like you may have a fuel supply problem in getting the proper amount of fuel to the fuel injectors. As you know, when you turn the key to on, the fuel pump is activated and the fuel system...

Related articles

2012 Subaru Outback vs. 2012 Chevrolet Impala: Which One Should I Buy?
When you compare a 4-door sedan versus a 4-door wagon, there are going to be some obvious differences. Even though the Outback looks car-like, the ride, the handling, and the mileage are going to make it more similar to an...
The Best Used Cars to Buy That Can Be Towed Behind an RV
Summer Summer is a great time for a road trip, but often travelers like bringing all the conveniences of home along, in the form of an RV. Then they tow their car behind it – sometimes this practice is called...
The Top 5 Selling Cars in Alabama in 2012
2012 2012 was a great year in Alabama for auto manufacturing, but that wasn’t the only bright spot. Vehicle sales in Alabama were also robust in 2012. Nothing much changed in terms of the vehicle types that were most popular...