it could be that your head gasket is on its way out or you mixed two different kinds of antifreeze.look at your owners manual makesure you put in the right antifreeze/coolant.(yeah, there are different kinds)
Not sure what an EGV is. More info please.
Yes you can. A cracked block does not necessarily mean the car will overheat. If a block is cracked at a coolant jacket then coolant will leak out and the car will overheat if the leak is bad enough. If the leak is not very major or if the crack is at a point that does not have a coolant jacket then it will not overheat. A cracked block could leak oil, compressed air/fuel, coolant, or nothing at all and still be cracked. -R. Mesyef
the answer is that if you blow the head gasket your car will overheat if you are driving any distance at all. You should smell coolant and see signs of leakage. It could be that head gasket is fine but you have had the bolts around the cylinder head work lose or be improperly torqued down. If you do nothing but drive short distances and the gasket is leaking at back end of clylinder many times it will just lose coolant of course this is serious too . If you see coolant leaking it is many times serious not just a hose or fitting .
Nothing if you drain it out and flush the cooling system. Oil is not a good coolant, and the water pump will have a hard time pumping it, so the vehicle will overheat if you do not remove the oil.
I've had this happen to me before. I had the water pump replaced after it had been leaking a little and my car overheated. We thought it might have been leaking again but turns out the mechanics had forgot to tighten something. I would have them look at it once more to make sure nothing is loose and leaking your coolant.
Are you sure it isn't the hose leaking AT the thermostat housing? If the car ever overheated on you, there may be a warped head. If so, you're in a BIT of trouble. Let a mechanic look at it. A consultation should cost you little or nothing.
How the water pump looks means nothing. If it is leaking, noisey, or is not pumping sufficent coolant, it is bad and needs replacing.
Most stop leak additives do nothing but empty your wallet. Replace the gasket that is leaking.
Nothing appears to be free
There are several reasons why your heat may not work. First your coolant system must be full with NO AIR pockets. There is a bleeder valve for the coolant system, in the area of the coolant recovery bottle, by the strut tower and the firewall. Have the vehicle running and open the valve, be careful coolant can be hot. Make sure you are full of coolant by checking the recovery bottle. If nothing comes out of the vent then you need to wait till coolant comes out.Another problem could be the heater control valve and or the thermostat. They are in the front center on top just under the cover and the air intake.The water pump might or the thermostat housing might be leaking, creating a leak that will allow air to enter. The older style of pumps were well known for leaking.
If air is leaking out, obviously the pressure will decrease to nothing. Find the leak and fix it.
Nothing....just call someone to lick it !!