[Lithias]

Wow, thanks so much for this thread, went outside and noticed my primary reservoir was half full and the surge was bone dry. Went and picked up some coolant asap. Never had an overheating issue or anything.

Please do go check your coolant levels guys! No leaks here guess it does just evaporate.

[Clearly_Canadian]

Originally Posted by buck50

Sound to me like you added non-Dex-cool coolant with factory fill dex-cool.
Not a recommended thing to do. Google it and you'll read all kinds of reasons why not a good idea.

Unfortunately, it was late in the evening and due to COVID, not many options. Had to make a call. Figured it was better to run the stuff that said it was compatible than just adding water. The Juice was not worth the squeeze.

Originally Posted by Lithias

Wow, thanks so much for this thread, went outside and noticed my primary reservoir was half full and the surge was bone dry. Went and picked up some coolant asap. Never had an overheating issue or anything.


Please do go check your coolant levels guys! No leaks here guess it does just evaporate.

I know right... I am a firm believer in "there is no stupid questions" and this is why. I am not a mechanic, however, I have been working on cars since I was in diapers. However, with technology today, it makes it harder to diagnose things without being an engineer. Most of my other cars didn't have a "Bi-level surge tank". I didn't have any issues either, it just seemed odd. Great way to learn.

[Yellow Beast]

Ive never had coolant evaporate before but according to the manual I just read that the coolant in the surge tank is a mixture of dex cool and water if it is low. It'll evaporate quicker if driven in warm climates. Checked mine and both are at the right level. I'm in the northeast but I'm still asking myself why would GM use a coolant that will evaporate?

[ctrlz]

Originally Posted by Mark114

That seems unusual. The radiator cap will let the system pressurize but I don't think it should allow a vacuum to form. Under vacuum the system should draw fluid from the reservoir which isn’t sealed. You might want to have the cap checked.

I agree with this.
I would not be content with just adding coolant. I think there may be an underlying problem.

Reservoir cap not venting properly is most likely. These are cheap to replace, while some say they can be readily cleaned by soaking in vinegar. You can test for one-way flow with compressed air. The one-way direction is air passing from outside to inside of cap.
The hose which leads from the radiator to the overflow reservoir should be checked for kinks/clogs. Kinks more likely.

The reservoir cap should hold pressure while the coolant is hot and expands. This keeps a pressurized dead space over the coolant and forces it back into the system. When the coolant cools and contracts, the reservoir cap should allow air into the reservoir so the coolant easily drains back to all the lower points. This is why these tanks are always at a high point.

[Wierd Harold]

Don't piss around asking for advice or it will cost .once the hotter weather gets here ,this will be a big inconvenience and bucks as well as leaving u stranded.get her in and have a pressure test done the coolant is going somewhere.check the bottle of coolant you purchased to see if it is compatible with dexcool.

[Clearly_Canadian]

Originally Posted by Wierd Harold

Don't piss around asking for advice or it will cost .once the hotter weather gets here ,this will be a big inconvenience and bucks as well as leaving u stranded.get her in and have a pressure test done the coolant is going somewhere.check the bottle of coolant you purchased to see if it is compatible with dexcool.

So The problem is still there. Funny how the lower tank is still bright yellow and the top is still pink. The two have not mixed yet. When I crack the rad cap for the surge tank it sucks air in and the hose goes back to normal.

I have an appointment on Monday to bring it in for an oil change. I will ask them to pressure check it.

For the time being I will continue to monitor.

[L78toLT1]

The lower reservoir is vented, not sure if you can see the holes with it installed, but there are, I believe, two ~ 1/8 vent holes at the top of the lower tank. I found that if I fill mine to the "full" level prior to a track day, I will lose a couple of inches from the bottom tank, presumably thru the vent holes. I have started keeping mine at the " low" level, and it stays there, regardless of the type of driving. The car never gets hot, it bumps against the thermostat and stays at 160.

[ctrlz]

Originally Posted by Clearly_Canadian

I have an appointment on Monday to bring it in for an oil change. I will ask them to pressure check it.

Shoot a cell phone video of this in case you cannot replicate it for them on Monday.