Coolant change issue

[Dave Sherman]

Changed the coolant in the Traverse yesterday. Owner's manual says when filling the radiator, leave the pressure cap off, run the engine until the upper hose gets warm (thermostat opens), top off radiator as necessary, and replace the pressure cap. I've done that, twice. When the engine cools off, it's still low in the radiator, though not as low the second time. The hose to the recovery tank is clear, and the level in the recovery tank goes up and down.

Is it safe to assume it will eventually burp any remaining air out itself? The service manual didn't give a different procedure. It's just the first vehicle where I've refilled the cooling system and it required topping off the radiator multiple times.

On a related note, I ran it longer the second time with the pressure cap off, and when it got up to about 190F on the scan tool, I started seeing bubbles at the filler neck. I let it get up to 205F, and the bubbles were more frequent. Could it have been boiling in the engine? I shut it off and the bubbles stopped.

Things are normal otherwise, no overheating, no leaks, fans turn on at 218F(!) and it cools down to 205 where they turn off.

 

[Olas]

If the thermostat is working and the fans are blowing hot all the time then you're golden.

If you've driven the car with the heater controls set to the hot position for long enough that the car gets up to temperature, then all of the bubbles will have bled/burped themselves into the recovery/overflow tank.
Constant hot air through the vents confirms its bled properly.

 

[SteveSRT8]

NOT always true.

Wildly platform specific, for instance my car requires a bleed to be opened near the thermostat. Some must be vacuum filled to prevent air pockets. Our service vans require the top hose to be the fill point.

Worth the trouble to look it up and get the specific procedure for your platform...

 

[mclasser]

Unless the Traverse is different, bleeding the air out of the system entails taking off the rad cap, setting the heat all the way to hot (90 deg if have auto climate control) and revving the engine to 2500 RPM or so several times until the cooling fans cycle through at least twice (thrice for extra good measure). Keep topping off the rad as the level falls during this process. It helps to have the front end jacked up so the air escapes more easily. Once done, top off the overflow and you're done. Check to make sure the heat is toasty, temp gauge is normal and you don't hear any water rushing sounds behind the dash -- indicative of air still in the system.

 

[Dave Sherman]

The factory service manual didn't have anything beyond the procedure I already said. Didn't even mention setting the heat to high, though I did. I was concerned when it started bubbling with the cap off because it seemed like air burping out at first, but it kept going and getting more frequent which made me think it was possibly boiling in the engine.

No gurgling sounds, the heat is plenty hot, and the recovery tank was slightly lower today. Unfortunately, GM gets an F for putting the radiator cap out of sight under the big plastic cover with lots of fasteners holding it on. I guess they didn't want you to get to it too easily.

 

[GS1000S]

You should be fine. Hold at a fast idle when warm several times to circulate coolant and cycle thermostat, topping off radiator when needed. Then fill the coolant recovery tank and let engine cool and it should pull in a small amount of additional coolant when it cools to outside temp. Top off radiator when cool if needed and you should be good to go.