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Rad Cap or Leaky Hose/Clamp

Hey all, so for the past week or so, I’ve been having problems with my cooling system. (May or may not be related to my air valve stuck open code, just thought I’d mention it.) First thing that drew my attention to the problem was smoke (or steam) coming from under the hood, I let the car cool off, and drove home. During this time I also noticed the heat stopped working. I went to get some coolant in another car and filled it up. Smoke went away, and heat started working again.

Later the same day I checked the resivoir and it looked low so I figured the radiator sucked all the coolant up, so I refilled the resivoir tank. I spilled a nice amount when doing that, and the steam came back. It cooled down again and no more steam, figured it burnt off. The next few mornings on my first drive of the day ONLY, I saw steam. Thought it was the condensation mixing with the leftover coolant that I spilled since it didn’t happen at all until the next morning.

Today was the first time it started steaming at night, and the heat stopped working again, even though the resivoir level was mostly full. I let the car cool down, and then I added more coolant and the heat started working again, no more steam either. Looked under the hood once I got home, abt a 20 min drive, resivoir was nearly empty even though car was still warm. No visible leaks on the smaller resivoir hose but there are puddles under the hood.

I’ve read it could be a leak of course, but also the Cap could be preventing the right pressure to suck fluid back in radiator after expanding into the surge tank, or something causing the tank to boil over…

Any ideas??

Car is a 2013 Chevy Sonic with 68,000 miles. Coolant has never been drained/refilled since I bought the car new in 2013.

Thanks for all your help.

Most assuredly you have a leak somewhere. Just have someone look to locate the leak. Could be a hose, could be the radiator, or could be the cap leaking but have it checked. When the coolant gets low, one of the symptoms is you will have no heat. Same problem, you are losing coolant and that can ruin an engine.



Any ideas??
Not often, but sometimes I have one…

I looked at an 8 page GM Technical Service Bulletin (with color picture and arrows!) written to help GM technicians diagnose overheating conditions in
2011-2014 Chevrolet Cruze and 2012-2014 Chevrolet Sonic cars with 1.4L Engines.

Is that your engine ? Some of these have been found to leak coolant onto the ground from the water pump weep hole or shaft.

There are instructions for determining a leak (telltale evidence) even if it’s not leaking at the moment.

Do you remember receiving a letter? Apparently a letter was sent to owner’s explaining that owners suspecting this condition should have their vehicles inspected and it’s possible that warranty replacement could be covered up to 10 years and 150,000 miles if it’s a leaker.

Are you able to look into the top of the radiator with this cooling system configuration? If so, double check the radiator isn’t low. It’s possible w/some cars when leaks develop – my own Corolla and truck for example – for the plastic tank to be full, but the radiator to be nearly empty. If you aren’t sure, suggest to stop driving & have the car towed to a shop. Driving it in this condition could result in expensive engine damage if the cooling system isn’t working.