Car: Hyundai Sonata Hybrid

Yesterday, before going into work I forgot to shut my car off. That was at 9am. Around 1pm, I received and email that my car was running so I went out to shut it off. Once I got outside, there was a large puddle of fluid under the car, gas tank empty, and battery dead.

I had a service come to jump the car and put fuel into it. As I went to drive home, I noticed the AC was not cold and the temperature gauge was all the way up. I pulled over and let the engine cool before continuing home. No weird noises or any red flags.

Upon getting home, I let the car cool down and popped the hood. First bad sign was my coolant reserve tank was empty. Secondly, there appeared to be coolant residue near the small hole in the coolant reservoir. Finally, I decided to open the radiator cap and it was bone dry.

I will note, the temperatures where I live we’re around 90 and the car was in the sun... extremely hot.

What exactly could’ve caused the car to leak all the coolant fluid?

Coolant can leak just about anywhere it travels through the cooling system.

For example:

  1. It can leak externally at the hoses, water pump, gaskets, and/or heater core to name a few.

  2. It could also be that the cooling fan was not operating and that caused the engine to overheat while sitting, pushing coolant out of the resevoir.

  3. The coolant could also have been consumed and went out the exhaust via a bad head gasket, crack in the head, or block.

In your situation, since it obviously ran hot for a long time, I think the best plan of action is to 1st pressure test the system to look for external leaks, and then have a chemical block test performed to see if their are any combustion gasses present in the cooling system.

You will want to verify if the worst case scenario has happened (cylinder head or gasket is bad), before fixing any other major repairs. Depending on what it may be, some or all of the work may overlap.

  • Would I be able to put coolant back into the reservoir and see if everything goes back to normal? Assuming I put the same one in as before. – Nick Jul 11 at 19:14
  • Sure you can. I just wouldn't fill it up with coolant, drive 10 minutes and then determine everything is going to be okay. Start with shorter trips and go a little further each time. Without testing anything, it leaves that dark cloud of uncertainty that rides shotgun with you for a while. – Milison Jul 11 at 23:48

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