Sometimes it smells like coolant coming threw the vents when the ac is on. What would cause this?

 

Could be the heater core leaking.

 

cracked head or head gasket leaking is a possibility, If you pull the dipstick and notice bubbles or white stuff means youve got coolant in the oil and problems to fix

 

If the heater core is leaking that might do it, but you'd also see coolant on the ground under your truck.

 

Isn't the heater core located behind the dash board mounted against the firewall. Generally that is the location and it usually make the carpet in the passengerside of the truck damp if the leak is real bad. I maybe wrong on this since I haven't had this problem in any of my Silverados.

 

my coolant level is fine though

 

If you have a pin hole in the heater core you won't loose much coolant and it would give off a slight coolant smell

 

Hmm, i'll have to check that out