Antifreeze leak and engine temperature gauge acting weird

Hi everyone,


I own a 2011 Chevy Aveo, 50k miles.


5 months ago, while driving on the highway, the engine started to overheat and temperature gauge approached the maximum. I stopped at the closest garage, they found an antifreeze leak, changed the thermostat housing and radiator cap. Car worked fine for the next couple of months after that.


For the past few weeks, I've noticed a sweet smell when I turn on the heat. After a quick research on the Internet, I found that this could also be caused by an antifreeze leak. That being said, there is no sign of the engine overheating.


I brought my car to the garage I usually go to (not the same one mentioned before). They said they found a small leak and suggested we start from there before taking a look elsewhere. I've been going there for a few years and I trust them so I didn't really ask any questions. However, when I received the bill, I realized that they had actually changed the thermostat housing (which had been changed four months ago). I didn't notice this on the spot, only when I came back home on Friday evening.


And now, the smell is still there. It's not constant. If I let the heating to the first level, I'll smell it maybe for 30 seconds, than it's fine, and it comes back after. Also, the engine temperature gauge has been acting weird this weekend. It goes a little bit over the middle (which it doesn't normally do) and sometimes drops a bit, but mostly stays where it should be. Another bizarre thing is that yesterday morning, I started the car after a freezing night and the gauge went up near the middle in only a minute (but stopped there), while usually, it takes a lot more time.


With all of that said, I have a couple of questions :


1- From where else could this smell come from?


2- What could cause the engine temperature gauge to act weird?


3- Is there a possibility that the thermostat housing broke twice in 4 months? Could the garage who did the first reparation be at fault?


Thanks for your help!

I am going to venture that a few things are happening all at the same time.

If you're not already aware, 2009-2011 Aveos have an engine with an engine oil cooler. When the seals deteriorate (usually after about 4 years), oil gets into the coolant, forms an sludgy emulsion, and softens the rubber in the cooling system hoses, water pump gasket, and softens the plastic in the coolant recovery tank. Oily sludge also builds up inside the coolant recovery tank, and also probably on the electrically-controlled thermostat.

1) If i had to guess, I would wager that the sweet smell is coming from a slow leak in the coolant recovery tank that only starts to leak when the pressure builds up.

2) Engine temperature gauge could be acting erratically due to sludge build-up inside the thermostat, a bad cooling system temperature sensor on the thermostat housing, or a generally bad ground connection on the engine wiring harness to chassis ground connection right beside the underhood ECM.

3) The thermostat housing is made of plastic that is very brittle, and any attempt to replace the thermostat will often crack the thermostat housing when the screws are tightened. If you have to replace the thermostat, be prepared to replace the housing at the same time. There are some aftermarket metal housings available at a reasonable price on Amazon. They might be a good idea to use if you are frequently touching the thermostat.

That's my 2 cents. And don't forget, if you're going to keep the car for any length of time, it's a good idea to replace the engine oil cooler, and do a thorough flush, to stop the cooling system rubber and plastics from softening and leaking.

Deano

Quote:

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Originally Posted by Deano

I am going to venture that a few things are happening all at the same time.

If you're not already aware, 2009-2011 Aveos have an engine with an engine oil cooler. When the seals deteriorate (usually after about 4 years), oil gets into the coolant, forms an sludgy emulsion, and softens the rubber in the cooling system hoses, water pump gasket, and softens the plastic in the coolant recovery tank. Oily sludge also builds up inside the coolant recovery tank, and also probably on the electrically-controlled thermostat.

1) If i had to guess, I would wager that the sweet smell is coming from a slow leak in the coolant recovery tank that only starts to leak when the pressure builds up.

2) Engine temperature gauge could be acting erratically due to sludge build-up inside the thermostat, a bad cooling system temperature sensor on the thermostat housing, or a generally bad ground connection on the engine wiring harness to chassis ground connection right beside the underhood ECM.

3) The thermostat housing is made of plastic that is very brittle, and any attempt to replace the thermostat will often crack the thermostat housing when the screws are tightened. If you have to replace the thermostat, be prepared to replace the housing at the same time. There are some aftermarket metal housings available at a reasonable price on Amazon. They might be a good idea to use if you are frequently touching the thermostat.

That's my 2 cents. And don't forget, if you're going to keep the car for any length of time, it's a good idea to replace the engine oil cooler, and do a thorough flush, to stop the cooling system rubber and plastics from softening and leaking.

Deano

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Thank you so much for you answer!

I understand that it may be hard for you to say since you can't see the car, but what you would precisely ask the mechanic to do/change to try to fix the problem?

I'm afraid it might be a heater core leak, but before paying for such a costly job, I'd like to consider other options.

Thanks again,

The garage should do a coolant system pressure check to find the leak if you can smell coolant. Heater core leaks are very rare. Most likely the coolant tank, hose, pipe or radiator…….unless the water pump is on its way out. Any of these is much cheaper than a heater core replacement.
I doubt the previous garage is at fault for anything