Also check to see if the smoke that comes out of your exhaust is white in color. If it is that means that your engine is trying to burn the antifreeze.
ANSWER
Sporadic temp guage and heater not working is one sign. This is also a sign of low fluid. Water blowing out of radiator cap is another sign. Especially if it is immediately after startup. A leakdown test is another metod that is best left to qualified technician. In this test they can determine if air is escaping out of cylinder and into radiator or is escaping from one cylinder to the adjacent cylinder.
If your oil level raises suddenly. If you loosen oil drain plug and antifreeze begins dripping instead of oil.
There are many many ways to find out. Some best left to the pros.
sounds like a blown head gasket.
have a mechanic sheck for a blown head gasket or a craked head
In my 1993 Ford F-150, I had oil in the breather due to a blown head gasket.
Remove transmission oil pan for acces to filter Replace fluid, filter, and gasket
Blown head gasket, cracked hed or cracked block
Blown head gasket
The cost to repair a blown head gasket on a 1993 Ford Explorer can range anywhere from $800 to well over $1,000. It usually takes between 7-10 hours of mechanical labor to fix a head gasket. Pricing will vary depending on the labor rate as well as the labor time.
You pull the head off and change the head gasket. There is no treatment for a blow gasket, exept changing it. Its a pretty huge job I would suggest getting it at the garage and get a quote.
White smoke from the exhaust is the most common sign. A compression test will tell you allot.
The white smoke means coolant being burned. So the chances that its a head gasket problem are pretty high.
cracked head or blown head gasket Coolant is entering the combustion chamber through a hole in the head gasket.
Blown fuse, defective heater control switch, bad resistor pack, loose or disconnected wire.