Two problems related to engine belts and pulleys have been reported for the 1998 Mercury Grand Marquis. The most recently reported issues are listed below.
Plastic intake manifold cracked and leaking coolant around thermostat area that squirts out under driving conditions and pools around fuel injection and contaminates electronics and serpentine belt and pulleys. Could leak to overheating and engine failure . Poor driving condition.
Serpentine fan belt & idler pulley / tensioner replaced due to noise.