How do you replace the head gasket in a 1991 Ford Explorer with a 6 cylinder engine?

Answer 1

Cylinder Heads Removal Rotate crankshaft to zero degrees top dead center (TDC) on the compression stroke. Disconnect battery ground cable. Drain engine cooling system. Remove air cleaner outlet tube to throttle body. Mark and remove vacuum lines to upper intake manifold. Disconnect EGR backpressure transducer hose from EGR valve to exhaust manifold tube, loosen lower EGR valve to exhaust manifold tube nut and rotate EGR valve to exhaust manifold tube away from EGR valve. Disconnect the throttle position sensor (TP sensor), idle air control valve (IAC valve), EGR backpressure transducer and EGR vacuum regulator solenoid electrical connectors. WARNING: COVER FUEL PRESSURE RELIEF VALVE WITH SHOP CLOTH TO PREVENT ACCIDENTAL FUEL SPRAY INTO EYES. Relieve pressure at the fuel pressure relief valve (Schrader valve). Remove fuel line safety clips. CAUTION: Cover fuel line ends with clean shop cloths to prevent dirt from entering opening. Disconnect fuel lines. Remove upper intake manifold as outlined. Discard old intake manifold upper gasket. Disconnect engine control sensor wiring retainers from rocker arm cover stud bolts and each fuel injector, and position the engine control sensor wiring out of the way. NOTE: Fuel injectors and fuel injection supply manifold may be removed with lower intake manifold as an assembly. Remove fuel injection supply manifold and fuel injectors. Remove ignition wires from spark plugs. Remove wire harness retainers from valve cover retaining stud bolts. Remove ignition coil and bracket from LH front cylinder head and set aside. Disconnect upper radiator hose and heater water hoses. Remove camshaft position sensor (CMP sensor) and housing. Disconnect engine control sensor wiring from engine coolant temperature sensor (ECT sensor) and the water temperature indicator sender unit. If LH (front) cylinder head is being removed, perform the following: Disconnect generator electrical connectors. Remove drive belt. Remove drive belt tensioner. Remove Power Steering support bracket and power steering pump as an assembly and set aside in a position to prevent fluid from leaking out. Remove oil level indicator tube retaining nut from exhaust manifold stud bolt. Rotate or remove oil level indicator tube from exhaust manifold. If RH (rear) cylinder head is being removed, perform the following: Remove intake manifold support. Remove valve covers. NOTE: Regardless of cylinder head removal order, the No. 3 cylinder intake valve push rod (6565) must be removed to allow removal of lower intake manifold. Loosen rocker arm seat retaining bolts enough to allow the rocker arm to be lifted off the push rod and rotated to one side. Remove push rods. Identify the position of each push rod. The push rods should be installed in their original position during reassembly. Remove lower intake manifold. Remove spark plugs. Remove exhaust manifolds. Remove cylinder head retaining bolts and discard. Remove cylinder heads. Remove and discard the old head gaskets. Installation CAUTION: Use care when scraping aluminum surfaces to prevent gouging which may cause leak paths. NOTE: Lightly oil all bolt and stud bolt threads before installation except those specifying special sealant. Place shop cloth in valve tappet valley to catch any dirt or gasket material. Clean cylinder head, intake manifold, valve cover and head gasket surfaces. If the cylinder head was removed for a head gasket replacement, check the flatness of the cylinder head and cylinder block gasket surfaces. Position new head gaskets, noting UP designation on head gasket face, on cylinder block using the cylinder head to block dowel for alignment. NOTE: Replace cylinder head to block dowel if damaged. Position cylinder heads on cylinder block over cylinder head to block dowels. CAUTION: Always use new cylinder head bolts when installing cylinder head or damage to engine may occur. Install new cylinder head retaining bolts: Tighten retaining bolts in sequence shown to 70-90 Nm (52-66 lb-ft). Then back off bolts 360 degrees. NOTE: When cylinder head retaining bolts have been tightened as outlined, it is not necessary to retighten the bolts after extended engine operation. However, the bolts can be checked for tightness if desired. Tighten the cylinder head retaining bolts to: 40-55 Nm (33-41 lb-ft) 85-99 Nm (63-73 lb-ft) Install lower intake manifold as outlined. Connect engine control sensor wiring to the engine coolant temperature sensor and to the water temperature indicator sender unit. Dip each push rod end in Engine Assembly .Install push rods in their original position. Install rocker arms, rocker arm seats and retaining bolts.Tighten bolts to 7-15 Nm (5-11 lb-ft). CAUTION: Rocker arm seats must be fully seated in cylinder head and push rods must be seated in rocker arm and valve tappet sockets prior to final tightening. Final tighten retaining bolts to 26-38 Nm (19-28 lb-ft). NOTE: If the original valve train components are being installed, a valve clearance check is not required. If a component has been replaced, perform a valve clearance check. Lubricate all rocker arms with Engine Assembly Lubricant. Install lower intake manifold as outlined. Install spark plugs if removed. Position valve covers on the cylinder heads and install retaining bolts. Note the location of ignition wire retainer stud bolts. Connect engine control sensor wiring to fuel injectors and valve cover stud bolts. Install upper intake manifold and intake manifold upper gasket. Install ignition coil and bracket assembly. Tighten retaining bolts to 40-55 Nm (29-41 lb-ft). Connect ignition wires to the spark plugs and ignition wire separators (12297) to valve cover retaining stud bolts. Connect intake air temperature sensor (IAT sensor), throttle position sensor, idle air control valve and EGR backpressure transducer or EGR vacuum regulator solenoid electrical connectors. If LH (front) cylinder head was removed, perform the following: Install or rotate oil level indicator tube to exhaust manifold retaining stud bolt. Tighten nut to 16-20 Nm (12-15 lb-ft). Install power steering support bracket and power steering pump assembly. Tighten retaining bolt to 40-55 Nm (29-41 lb-ft). Install drive belt tensioner. If RH (rear) cylinder head was removed install intake manifold support. Install generator. Tighten long retaining bolt to 48 Nm (35 lb-ft) and short bolt to 37 Nm (27 lb-ft). Install the drive belt. Connect fuel lines as outlined. Install fuel line safety clips. Connect upper radiator hose and heater water hoses. Tighten clamps securely. Connect vacuum lines to premarked locations. CAUTION: Engine coolant is corrosive to all engine bearing material. Replace engine oil after removal of a coolant carrying component to help prevent future failure. Drain and change engine oil. Install air cleaner outlet tube to throttle body and engine air cleaner (ACL). Install crankcase ventilation hose to valve cover. CAUTION: This engine has aluminum components and requires a special corrosion inhibiting coolant to avoid cooling system damage. Fill and bleed engine cooling system. Connect battery ground cable. Start engine and check for coolant, fuel, oil, vacuum and exhaust leaks. Check, and if necessary, adjust the accelerator cable and speed control actuator cable.