Coolant boiling in reservoir

[Dmh1980]

I have a 2009 lucerne cxl and while in traffic the other day i see smoke coming from under the hood. So when stopped the car and looked under the hood the coolant in the reservoir was boiling over. Besides the smoke there was no indication anything was wrong. Temperature guage wss normal what's causing this? Also im sure it may be related, but i got a message on the dash today saying that the engine was hot a/c off guage was on cold.

 

[2007LucerneCXL]

The temperature gauge sending unit may be bad or connections is the first guess. The overheating may be the radiator cap, thermostat, check for coolant around the water pump or some type of blockage in the coolant system. Check the oil and make sure that there is no coolant in it. Depending on age of the coolant it may be a option to replace at this time, this is at least items to start with.

 

[CorvairGeek]

I assume this is a V8?

 

[polarzak]

As someone mentioned, check your oil to ensure no coolant is evident. Looks for white sludge inderneath the oil filler cap. A cracked head or head gasket will usually cause bubbles in the reservoir.