Hello all its been a while since I have posted. In the last week or so I have noticed some sloshing sounds from inside the cabin (2007 LS Monte FFV). I later stopped getting heat at idle (only at idle) and figured there was some air in the system. I took the rad cap off and saw some bubbles added some dexcool and figured that was it. Heat worked fine after this but sloshing started coming back and changed the rad cap (hoping this is it). I then noticed bubbles in the overflow tank for the first time but these went away after I drove about 10 miles (after changing the cap). I have heat and haven't had heard anymore sloshing so far. I am hopeful it was just the rad cap as it was not pulling dexcool from the reservoir with the old cap. My question to the experts is... if its not pulling dexcool from the reservoir does that indicate a bad cap? Could the air come from a bad cap or does it mean my head gasket is leaking exhaust into the coolant? If so wouldn't I get over heating (no over heating so far)? Thanks for any and all input.

 

If you got a bad head gasket then it will overheat big time, like you can't get thru the drive thru a McD's I know because I just went thru that with a GM SUV with a 3400 after trying everything I finally replaced the Gaskets and problem solved.
You may need to bleed the cooling system to get the thing working again. If the reservoir is working and not over filled you should see the coolant level at the tank markings.
When was the last time you did a complete system flush? Something to consider.
Check the floor on the passengers side of the car and see if the Carpet is wet if so you might have a bad heater core.
Sloshing can be water in the doors. Check to make sure the drain holes are open in the doors.
Hope this helps some!

 

@drivernumber3 Thanks for all the tips and info felt better after reading your reply think your right that it isn't head gasket since no over heating issues so far. After buying a new ACDelco rad cap the bubbles in the coolant overflow tank stopped (after 10 miles) and now I have noticed that the level of dexcool in the tank went down significantly. I am actually excited about the level of the tank changing since that means it is pulling dexcool from it which it wasn't doing before (I had to keep putting dexcool into the fill neck). A few years back I changed the crossover pipe gaskets and a certain amount of coolant never went back in well its finally all back in now. Apparently it was all just a bad rad cap as all seems well now. By the way the new cap says 18PSI on it and the old says 15PSI any thoughts on that? Maybe was the wrong cap to begin with or it just went bad over time? I think your right I should flush the system since I never did before only 75K on it but its def past 5 years old Does dexcool really break down if the car just sits a lot? Oh and I did check the floor not wet and no water in the doors. Thanks again for your quick reply!

 

I am a big fan of doing the service on the vehicle when it needs to be done.
Oil changes, Trans fluid changes, flushes. all that stuff breaks down.
I used to travel with a vehicle extensively and always did the maintenance. I could tell by the sound the car was making what was going bad on it.
But I always did the maintenance to make sure I didn't get stranded. I got several vehicles to last 390K before I switched to another one.
I would flush the system every 2 years or 50K and change all the hoses and the thermostat too. Some useful info.

 

@drivernumber3 Wow 390K is impressive! That says a lot for your maintenance record! Thanks for the pics convincing... I guess its hard to tell what's going on inside your engine with build up and rust etc. Seems like a good idea to change all fluids. I will plan to do that soon for now just glad the heater works and still checking for leaks. What are your thoughts on using the petcock vs lower hose? People are always warning against it saying they are easy to break. Last time I used the petcock no issues.