Why does my car only heat up when I'm on the highway?

TONYREXX97

MEMBER
2003 CHEVROLET IMPALA
3.4L
V6
AUTOMATIC
229,000 MILES

Defrost seems to be working. My last mechanic said about 3 months ago that there were a couple of leaks but I forgot where though. The car has got nearly 230,000 miles on it. You can hear a loud engine burring noise when its cold outside on idle and gets louder when you accelerate or revv. Also, the colder it is outside, the louder the engine. Wiper fluid sign has been on for about a month as well. Car starts perfectly fine everytime though.

1 Reply

FREEMBA

MECHANIC
1,152 POSTS

When you say that " it heats up only on the highway, " do you mean that the heater only works when you are driving down the highway or that the engine seems to overheat when driving?

If the heater only works when you are driving down the highway, the most likely problem is that your cooling system is low on coolant. This would indicate that you cooling system has a leak. Filling the system with coolant will restore the heater to its proper operation, however, there is still the matter of the leak. To find the leak, have the cooling system pressure tested at a local garage (shop around for best price). Find and repair the leak, fill the system with coolant and then the heater should work just fine.

If the engine is overheating while driving down the highway, you'll still need to have the system pressure tested for leaks. Also check the belts, hoses and cooling fans for proper operation.