Cylinder Head Installed
See Figures 1, 2, 3, 4, 5, 6 and 7
The valve stem seals on most engines covered by this guide may be replaced with the cylinder head either on or off the engine. The removal procedure with the cylinder head installed utilizes compressed air in the cylinder to hold the valve in place and keep it from dropping into the cylinder once the valve key, cap and spring are removed.
If air pressure is lost while the valve keepers are removed, the valve will drop into the cylinder. If this happens, the cylinder head must be removed in order to recover the valve.
- Disconnect the negative battery cable.
- Remove the rocker arm cover.
The cylinder must be on at TDC of its compression stroke in order to follow this procedure. On the compression stroke, the cylinder's valves will be closed allowing the air pressure to hold the valve in position. The engine must therefore be turned slightly for each cylinder's valve seals.
- Remove the rocker arm and pushrod assemblies from the cylinders on which the valves are being serviced.
- Remove the spark plug from the cylinder which is on its compression stroke and install a spark plug air fitting adapter with an in-line gauge set between the adapter and air compressor. Apply compressed air to hold the valve in place.
- Compress the valve spring using a suitable compressor tool and remove the valve key. Carefully release the spring tension, then remove the valve cap and spring.
If the air pressure has forced the piston to the bottom of the cylinder, any removal of air pressure will allow the valves to fall into the cylinder. A rubber band, tape or string wrapped around the end of the valve stem will prevent this.
- Remove the old seal using a suitable removal tool.
- Install the new seal using the valve stem seal tool.
- Install the valve spring and cap, then compress the spring and install the valve key.
- When the valve springs are properly installed, release the air pressure from the cylinder using the gauge set, then remove the spark plug adapter.
- Install the spark plug and turn the engine sufficiently to work on the next cylinder. Repeat the above steps until all seals are replaced.
- Install the rocker arm and pushrod assemblies, then install the rocker cover and connect the negative battery cable.
The valve stem oil seals are replaced as a part of normal valve service any time the valve stems are removed from the cylinder head. Refer to the valve procedure in this section for seal removal and installation when the cylinder head has been removed from the vehicle.