Valve Seat: Service and Repair

Valve Seat, Refacing

Special tools, testers and auxiliary items required

• Depth Gauge

• Valve Seat Refacing Tool

Procedure

• When repairing engines with leaking valves, it is not sufficient to reface or replace valve seats and valves. It is also necessary to check the valve guides for wear. This is particularly important on high mileage engines. Refer to => [ Valve Guide, Checking ] Testing and Inspection.

• Only reface valve seats enough until a perfect contact pattern is obtained. The maximum permissible refacing dimension must be calculated before the work is carried out. If the refacing dimension is exceeded, the function of the hydraulic lash adjusters can no longer be guaranteed and therefore the cylinder head should be replaced.

- Remove the camshafts. Refer to => [ Camshafts ] Service and Repair.

Maximum Permitted Refacing Dimension is Calculated as Follows:

- Insert the valve and press it firmly against the seat.

• If the valve is to be replaced as part of a repair, use a new valve for the calculation.

- Measure the distance - a - between the valve stem tip and the upper edge of the cylinder head.






- Calculate the Max. permissible refacing dimension from the measured distance - a - and the minimum dimension.

Minimum Dimensions:






The measured distance minus the minimum dimension = the MAX. permissible refacing dimension.

Example:






Refacing the Intake Valve Seat











Refacing the Exhaust Valve Seat











• 1 To calculate the maximum permissible refacing dimension.