that is probably an oil pressure switch that you see. coolant temp sensor is usually near the thermostat in the manifold.
The 2002 Ford Explorer 4.6 liter engine oil pan can be removed without removing the engine. The oil pan can be removed from the bottom of the engine.
Coolant recovery tank
The engine coolant capacity with A/C is ( 8.6 quarts / 8.1 liters ) without A/C ( 7.8 quarts / 7.4 liters ) according to my 1995 Ford Explorer owners manual
According to the 2000 Ford Explorer Owner Guide : The engine coolant capacity is 14.9 liters ( 15.7 quarts )
Any coolant hose could be leaking. Clean the engine bay, removing dirt and grime. Watch closely to see where the leak is. Also check all hose clamps to make sure that they are tight.
On a 1997 Ford Explorer : CHECK ENGINE is just to the left of the " C " on the engine coolant temperature gauge ( Helpfull )
Yes , on my 1995 Ford Explorer XLT there is a cold fill mark . When the engine is cold the coolant level should be up to the mark
There is an engine coolant tank , made of plastic , in the engine compartment on the passenger side that has a mark on it for the cold level of your engine coolant , maintain the coolant level up to that mark when the engine is cold
depending on the engine there is not one let the engine run with the coolant cap off and watch the res level
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I believe your engine coolant level is LOW
Engine fail safe is on the 4.6 L V8 engine only - ( you have lost your coolant ! ) - find and then repair the cause of your coolant loss