As most would know this is typically a sign of air in the coolant circulating through the heater core. My 2008 2.2L started doing this about two years ago. At first just on cool mornings when you first start it up and drive off.

During the summer months I didn’t notice it any more, so I just figured I got a little air in the system and finally burped it out. The following winter I started noticing it again.

I checked the coolant reservoir, level was right on. Pulled the Radiator cap, coolant was right up to the cap opening. No sign of any external leaks.

Lately I noticed it started making this sloshing sound when the temp gets above 215 and you moderately accelerate.

So I'm thinking, no visible leaks, reservoir level stays the same, coolant at the radiator cap when removed, hose between cap and reservoir is open and moving coolant, so what’s left…Hum, bad head gasket? But wait a minute, if the head gasket were bad, wouldn’t the coolant reservoir level either increase from being over pressurized or be sucked dry?

Well what else could cause this problem and was the cheapest thing to try…Well how about the Radiator Cap? If it weren’t properly sealing it might cause the coolant to start to boil in the system and might cause this sloshing noise but it wouldn’t account for it at around 100.

So I figured what the heck, threw a new A/C Delco cap on the next morning. I still noticed the sloshing that evening on the way home. So I thought, lets see what happens in the morning. Well low and behold, the next morning nothing, no sloshing. So far its been a week and nothing in the morning or when hot. The reservoir is down about a cup or two.

I pulled the old cap back out of the box and did a simple pressure and vacuum test on it…Seems the cap will not fully seal no matter how much pressure I put on it. On the vacuum side it flowed sluggishly.

In comparison, the new cap would seal with just a little pressure and flowed freely on the vacuum side. Hopefully this was the problem. Yes, I know, I need to flush the system. Next on my list.

Just thought I’d pass it on

P/N 15042975 (RC85) for the 2.2L but appears to be used on quite a few GM vehicles so probably the same for the 2.0 & 2.4

 

excellent thanks for the input and resolve solution to the gurgle under the dash!