air in cooling system

[belldave]

I have an intermittent heat problem (inside the car) which I fear is masking a greater problem. The temp gauge, and thus heat inside the car, run normally in the city but drops to near minimum (thus cold air inside the car) after around 10 mins on the interstate. There appears to be air entering the cooling system which is causing this: I have twice "burped” the system, following which the engine and cooling system run normally (radiator hot, radiator fan blowing hot, no bubbling in water reservoirs, all cooling system pipes hot) until I’ve been at higher speeds for 10 mins or so, when it drops again – presumably due to more air being sucked into the system. The coolant levels do not appear to be dropping, nor is there any sign of coolant leakage from any area. Is it possible/likely that these symptoms point towards a head gasket or cylinder head problem? If so, have you any idea of repair costs for these faults (I guess the labor charges will be the greatest) – or even whether it is worth repairing? Many thanks in advance.

[comp]

check the over-flow tank,hose, and rad.cap to make sure they are working correctly... if overflow hose not in coolant it will suck air
does it loose coolant? do you add?

[sparkypdr]

A blown head gasket can do various things, but if air is getting into the system due to it, then fluid must be getting out the same way. The question is where is it going? A small leak can instill enough air in the system to make it not heat inside the car well and not be noticable as far as coolant level goes. Check the oil to make sure that you don't have coolant in there and check to make sure that it isn't coming out of the exhaust. Cavaliers are notorious for blowing head gaskets. The gasket kit is a little over $100.00, you can probably get it put on for a couple hundred more (but not at a dealer). It is a hateful job to do yourself, but if you do, it will take a day to take it apart and another day to put it all back together if you are a novice like me. Oh . . . it helps to have small hands that can fit into tight places.

[comp]

if it is headgasket NEW HEAD BOLTS