Problem Reports

Engine overheating can result from coolant leaks which are commonly found at the thermostat housing gasket, water pump, heater return tube O-ring at the water pump, intake manifold gasket, and timing cover gasket. Our technicians recommend a complete inspection of the cooling system after any repairs are made to be sure there are no other leaks.

On the 3.9L V6, 5.2L V8 and 5.9L V8 the Oil leaks commonly from the valve cover gaskets, intake manifold gaskets (front and rear), timing cover gaskets, distributor O-ring, and the rear main seal area. Using fluorescent engine oil dye can be helpful in determining the source(s) of the oil leak.

The distributor pickup plate commonly fails causing intermittent stalling, or the engine may not start (usually when the engine is hot).

Various drivability problems can be caused by vacuum leaks. This engine has plastic tubes that become brittle and crack over time. These tubes can be replaced by normal vacuum hose but be careful when changing the Tee fittings or hose connectors because some have built in restrictor orifices (usually color coded). If the restrictions are missing, drivability problems will most likely result.

Black smoke from the tail pipe, hard starting, and a rough idle can be caused by a leaking fuel injector. With the air cleaner removed and the engine idling, fuel can be seen leaking from around the injector (O-ring leak), or from the nozzle (fuel injector leak).

The AC/heater (HVAC) system may unexpectedly switch to the defrost mode when accelerating. This system is operated by engine vacuum and should be inspected for any vacuum leaks if this problem develops.  There is also a revised vacuum check valve available to address this concern.

A surging or bucking during acceleration can be caused if the distributor is moved or mis-indexed. This is a result of the cam and crank position sensors being out of synchronization. Wear of the oil pump drive gear can cause similar symptoms because it allows excessive free play in the distributor drive. The distributor drive gear and bushing should be replaced if the rotor tip moves back-and-forth more than 3/16th of an inch when checking drive gear free play.

Internal leaks in the speed sensor or speed sensor gear adapter (speedometer adapter) are common. A revised speed sensor (white in color, old versions are black), used in production since November of 1993, solves the problem. If leaks develop between the sensor and the adapter or between the adapter and the transmission housing (transfer case if 4WD), a revised speedometer adapter is available.