So my car has this issue of overheating but only when im idling. I could drive for 6 hours and it wouldnt over heat till i come to a stop. We have changed hoses, thermostat, radiator cap, radiator and thermostat switch. We brought it to a mechanic and when i turn my ac on my fans dont turn on with it (he said with everycar they should) and the mechanic is a very close friend. I have three different radiator caps when i put my original on my coolant tubes stay soft and hot but my resovoir cap blows off (maybe its bad, the radiator cap). When i try the new one my resovoir cap stay on but the the tubes are rock solid and super hot. And one from the junk yard does the same thing. But anyways both times my car leaked coolant now idea where. I always have to fill my coolant up. And before you start saying headgasket we did a coolant exause leak test and it was good, sparkplugs looked good a little white but mechanic said they were fine. Exaust smells fine. But on the other side feels like i have a power loss (maybe a placebo) and some times it has a rough start. Ig any one can chip in that would be awesome, i dont know what to do next

 

I should also say that when im stopped my ac is cold but my heat is cold too, and whrn im driving my heat is hot like burning, and the ac is warm.

 

Just a thought since you've replaced almost everything in the coolant system except the water pump. I say this because its the only thing left for you to change and would make sense why the car is overheating at a stop because it has no passing air to help cool what little flow you have in the rad. Not to mention if you've done a leak down test that checked out, head gasket should be ok. I've seen water pump impellers completely corroded away like it dissolved in the coolant, failing to circulate coolant properly. Any leaking you have going on is obvious because there is too much pressure buildup from the heat. Also your no heat from the dash while stopped and hot af while driving could be because your impeller isn't circulating at low rpm and barely circulates at higher rpm passing all that overheated coolant through the heater core. Just my 2 cents, keep posted.

 

So today i changed out my coolant temp sensor and switch because i was passing the code p0118. That fixed that code, today it seemed to run alright. After running it for 2 hours the coolant in my over flow tank was boiling. I have talked to many mechanics and they are stumped as to why im losing coolant but my fans are never turning on even when i turn my ac on. This weekend im going to take it into a mechanic that will give me a full rundown and if its headgasket or pump ill change those instead of paying 1500$

 

Best of luck, maybe it could be something simple like the fan relay in the engine bay fuse box or a water pump. Curious of the outcome.

 

ill let you know i already check the whole fan system relays and fuzes. But we will see if the mechanic brings back anything!

 

More than likely it's going to be something with the fans not working. After an engine is hot the fans are what keep the engine cool when sitting at idle, the fans pull air through the radiator which remove heat from the coolant. This is sitting at idle, once the car starts moving cool air moving through the radiator takes over.

 

This weekend im gonna check headgasket with a cylinder compression test. Ill let you know till then ill just short my fan switch and drive like that!

 

ok so its been acouple of weeks! I changed the headgasket and it solved my problem. I may have blown my headgasket after over heating so much. I still have rough starts but for a car with 350, 000km on it im not suprised! I idled for 2 hours after a hard drive and nothing ran perfect!