C36 Billowing smoke and water gushing noises in Vents.

[Rocky]

Something is majorly wrong with my C36. I walk out from PetSmart and turn the key..the car stutteres and the check engine light comes on.

I get home and I turn off the car, thinking it might be a lose fuel cap so I re-tightened it and started the car...runs fine and no light.

Couple hours later I decide to get dinner and hop in the car, turn the key and it won't turn over. It turns over maybe once and then it stops with all the warning lights dimly lit. I try a few more times and finally it starts. Great I thought. Wrong. I notice that theres a pile of white smoke coming from the exhuast. It smells kinda sweet and I'm almost 100% sure it's antifreeze. I'm like "crap..engine block is cracked". So I drive it to my local Benz dealership at 11:00pm to drop it off. Weird thing is that as I drive, the smoke dissappears and no more smoke.

I stop at the parking lot and turn off the car. Walk over to get an envelope. Decided to turn the car on and it starts on the first turn. And smoke comes billowing out of the exhaust again.

Also when i'm driving, I can hear water gurgling and gushing sounds coming from the heating vents. Never heard that before and I know it's part of the problem.

The thing is I don't know what 's the problem. Anyone have any vague ideas? I honestly hope it's not a cracked block and it's just a water pump or something.