Q: The car is overheating and hissing when the AC is on

asked by on May 24, 2016

My car has started to overheat lately. When I drive with my air conditioning on, I start having problems if I come to a stop light for instance. The air turns from cool to warm and the hissing noise can be heard. Then, the engine starts overheating. I checked the level of coolant and it's fine. When I stopped my car in the traffic recently, it began to overheat but I pulled over and waited for it to cool down. Then it ran fine again. What could be the issue? Thanks.

Hello, if the car is only overheating when it is not moving then it is usually caused by an air flow issue through the radiator. Most of the time, this is caused by an issue with the radiator fan not coming on.

To diagnose this, I start by starting the engine and allowing it to warm up. As the engine starts to overheat the fan should come on. If it doesn’t, then the fan and the circuit need to be checked. Most of the time this is caused by a bad fan or fan relay. If you need to have this fixed, consider having a certified mechanic come to your home or office to diagnose your overheating problem accurately.

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


Experienced Mechanic?

Earn up to $70/hr

What others are asking

What Are Xenon HID Headlight Bulbs?
Xenon headlights (https://www.yourmechanic.com/article/what-are-xenon-headlights) are used in lights called HID (High Intensity Discharge lights). These lights do not use a traditional filament to provide the light but instead use xenon gas to produce the light. They provide more light output for...
Rattling noise in neutral. Car won't go over 30mph in 3rd.
Hi thanks for the question, man, there is nothing worse than a car that won't go anywhere when we want or need it to. It sounds like you may be having a problem with your catalyst converter in your exhaust....
How do I turn on the Sirius XM?
To turn on the Sirius XM system, press the Sirius button. Keep pressing this button to switch between SAT1, SAT2, and SAT3.
My Enclave has 160 K miles on it and It's time for a new serpentine belt.The car has a thumping sound when I drive it.i turned the
The fact that this sound disappears suggests that it could be potentially a loose motor mount (https://www.yourmechanic.com/services/engine-mount-replacement) depending on how severe the thumping sound is. If the serpentine belt (https://www.yourmechanic.com/services/serpentine-drive-belt-replacement) has not yet been replaced with 160,000 miles on it,...
ticking at idle
Hi there. The lifters are sticking causing the push rods to be loose and tap on the rocker arms. Put one quart of ATF in the engine oil and run the engine for 15 minutes at 3,000 rpm's. Then change...
Can't shift into reverse 1st or 2nd
Cable adjustment was the correct thing to try, but it won't help much if the ball and socket in the shifter is bad. The VW shifters use a nylon ball and socket joint that can crack, throwing everything off. Try...
1989 Chevy Celebrity dies, is it the fuel shut off switch?
First of all, I don't see that your vehicle is equipped with an inertia switch. Secondly, even if it were, it would not cause the problem you are having. A tripped inertia switch would prevent power from getting the fuel...
2004 lexus IS300 P0010 P0122 P2138 ALSO ERASED CODE P05OO AFTER CLEANING BOTH SENSORS IN TRANNY NOW CAR OVERHEATS IDLES @2000 in p
Hi Braxdon. Thanks for contacting us today. Of the error codes you've listed, the one that might be the root source of your problems is the P2138 OBD-II Trouble Code. The P2138 trouble code (https://www.yourmechanic.com/article/p2138-obd-ii-trouble-code-throttle-pedal-position-sensor-switch-d-e-voltage-correlation-by-andrew-quinn) indicates that the Engine Control...
Car starts n idles fine. When I put it in gear it stalls. I'm thinking transmission fluid problems? Also it "CLANKS" when shifting
The torque converter and torque converter lock up solenoid should be evaluated. Another possibility is an internal hydraulic leak in transmission seals causing pressure to apply both reverse and forward gears at the same time, lock up the transmission and...

Related articles

Signs of a Bad or Failing AC Compressor Relay
Common signs include inconsistent cooling, not hearing a click from the compressor turning on, and no cold air.
Symptoms of a Bad or Failing AC Fan Control Module
Common signs include cooling fans running for a long time or not at all, as well as weakened air flow. Without fixing, your car may overheat.
Symptoms of a Bad or Failing Evaporator Temperature Sensor (Switch)
Common signs include lack of cold air coming from AC, temperature fluctuations, and the AC compressor not activating.