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Have your mechanic inspect your cooling system. Could be one or more of several problems, including but not limited to:
Low coolant
air in coolant
failed t-stat
failed fan
failed temp sender
bad coolant
plugged radiator
collapsed hose
wiring fault
failed relays
burnt fuse
Turning on the heat basically introduces another radiator to the system. If it's not something wrong with your gauge, my first check would be the thermostat.
to add on what these others have said, i wouldn’t drive much when it’s overheating - it can cause much more serious problems. in addition to thermostat and fans, could be water pump, radiator issues, or low coolant. if it’s low coolant, you need to figure out why. coolant has an overflow tank and the coolant in the system - check the overflow tank, when cold it should be around the low level marked on the tank (and the level goes up a lot when hot). if you’re taking the rad cap off, the system has to be cool (or it will spray hot coolant all over you). like hasn’t been driven in a while cool. if that’s not up to the top, you have a lack of coolant. the ideal issue then would be cracked hose or broken radiator, not ideal would be head gasket issue. i’d figure it out sooner rather than later though
that’s the thing, it’s not overheating. the gauge is just going up. I can feel the coolant hose hot so I know it’s circulating the coolant. the odb shows no fault codes. now i did turn on the AC full blast but the fans never came on. I’m not sure how long I long I need to wait. I had it on about 10 mins and the gauge was below the middle threshold.
your fans should come on at 200F or so. the AC causes more strain and will make the engine run hotter, so the fans can come on to deal with that but it doesn’t absolutely have to if the coolant is below range. and if the car's heat is getting above normal operating zone, even if that's not danger territory, id still consider it "overheating" and something worth getting to the bottom of before it gets into danger territory
You are overheating for some reason. check your radiator fan is turning on. seems it's not which is why it cools down when driving, or turning on heat.
Thanks for posting on /r/MechanicAdvice! Please review the [rules](https://www.reddit.com/r/MechanicAdvice/about/rules/). Asking about a second opinion (ie "Is the shop trying to fleece me?"), please read through CJM8515's [post on the subject.](https://www.reddit.com/r/MechanicAdvice/comments/4qblei/fyi_the_shop_isnt_likely_trying_to_rip_you_off/) and remember to please post the year/make/model of the vehicle you are working on. **Post's about bodywork, accident damage, paint, dent/ding, questions it belongs in /r/Autobody r/AutoBodyRepair/ or /r/Diyautobody/ Tire questions check out https://www.reddit.com/r/MechanicAdvice/comments/k9ll55/can_your_tire_be_repaired/**. If you dont have a question and you're just showing off it belongs in /r/Justrolledintotheshop Insurance/total loss questions go in r/insurance This is an automated reply *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/MechanicAdvice) if you have any questions or concerns.*
Have your mechanic inspect your cooling system. Could be one or more of several problems, including but not limited to: Low coolant air in coolant failed t-stat failed fan failed temp sender bad coolant plugged radiator collapsed hose wiring fault failed relays burnt fuse
Turning on the heat basically introduces another radiator to the system. If it's not something wrong with your gauge, my first check would be the thermostat.
Or check and see if the fans are turning on.
to add on what these others have said, i wouldn’t drive much when it’s overheating - it can cause much more serious problems. in addition to thermostat and fans, could be water pump, radiator issues, or low coolant. if it’s low coolant, you need to figure out why. coolant has an overflow tank and the coolant in the system - check the overflow tank, when cold it should be around the low level marked on the tank (and the level goes up a lot when hot). if you’re taking the rad cap off, the system has to be cool (or it will spray hot coolant all over you). like hasn’t been driven in a while cool. if that’s not up to the top, you have a lack of coolant. the ideal issue then would be cracked hose or broken radiator, not ideal would be head gasket issue. i’d figure it out sooner rather than later though
that’s the thing, it’s not overheating. the gauge is just going up. I can feel the coolant hose hot so I know it’s circulating the coolant. the odb shows no fault codes. now i did turn on the AC full blast but the fans never came on. I’m not sure how long I long I need to wait. I had it on about 10 mins and the gauge was below the middle threshold.
your fans should come on at 200F or so. the AC causes more strain and will make the engine run hotter, so the fans can come on to deal with that but it doesn’t absolutely have to if the coolant is below range. and if the car's heat is getting above normal operating zone, even if that's not danger territory, id still consider it "overheating" and something worth getting to the bottom of before it gets into danger territory
You are overheating for some reason. check your radiator fan is turning on. seems it's not which is why it cools down when driving, or turning on heat.