About a month ago, I smelled a very faint smell of radiator fluid inside the car while the air was on. This happened twice, once on the highway when RPM’s were running fairly high/engine temp was slightly higher than usual, and once on sidestreets when I was driving at high RPM’s/in lower gears than normal (manual transmission). When I stopped the car it cooled down to normal level immediately and smell went away. I added coolant to the reservoir.
Then I noticed nothing for about a month, so I figured everything was OK.
Last week, my engine was running hot (usually is at 50% on the temp gauge, it was at 75%, where 100% is red zone), driving at low speeds. About 5 minutes before that, I had the heat on but noticed the air blowing in the car was not heated even though the engine was warmed up (I assume due to lack of radiator fluid flow through the engine). The car did not overheat, because I pulled over and added water, and later added some coolant. During that incident I did not notice any smell inside the car. At the end of the week, I noticed the car running slightly hot and checked the reservoir. It was low–most of the coolant I added had disappeared in just one week.
Usual things to check:
-radiator and all hoses are new
-no leaks under the car
-no white exhaust/smoke or smell outside
Other things about my car: It is a 1997 Honda Civic. Has never had any major problems, and it’s running smoothly, but it does burn oil. The first time I noticed the smell, it was just after I had driven on the highway with slightly low oil level (still on the dipstick, but slightly below the bottom dot. Not too far on the highway–about 20 minutes). Not sure if that could be related.