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caseydscott44
caseyd ... 3/22/2013
1991 Mercury Cougar LS 6Cyl3.8L - Engine
What is wrong when my car overheats and puts out no air driving down the road?
ive had the water pump, thermostat, and lower radiator hose changed and the cooling system flushed.
1 Answer
  • CVO
    CVO 3/23/2013
    Loss of coolant because of a coolant leak is probably the most common cause of engine overheating. Possible leak points include hoses, the radiator, heater core, water pump, thermostat housing, head gasket, freeze plugs, automatic transmission oil cooler, cylinder head(s) and block.

    Make a careful visual inspection of the entire cooling system, and then PRESSURE TEST the cooling system and radiator cap. A pressure test will reveal internal leaks such as seepage past the head gasket as well as cracks in the head or block. A good system should hold 12 to 15 psi for 15 minutes or more with no loss in pressure. If it leaks pressure, there is an internal coolant leak (most likely a bad head gasket but possibly also a cracked cylinder or engine block).

    It is important to pressure test the radiator cap, too, because a weak cap (or one with too low a pressure rating).

    For no air driving down the road, an insufficient coolant , trapped air in the cooling system might not have enough coolant to full fill the heater core.
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