MG MGB TOURER GHN5 Handbook page 69

Oil filler cap
Fig. 6
CRANKCASE EMISSION CONTROL
An air filter is incorporated in the oil filler cap (1). The cap and filter are renewed
only as a complete assembly.
Closed circuit
breathing
Control valve
Testing
Servicing
Fig.
6
Crankcase breathing is by a direct connection from the oil separator to the
carburetters. Servicing is confined to the oil filler cap, as recommended in the
maintenance summary.
Early cars: With the engine at normal operating temperature, run it at idling
speed. Remove the oil filler cap. If the valve is functioning correctly the engine
speed will rise slightly as the cap is removed, the change in speed being audibly
noticeable. If no change in speed occurs, renew the valve or service it as follows.
Remove the spring clip (2) and dismantle the valve. Clean all metal parts with a
solvent (trichlorethylene, fuel, etc.). If deposits are difficult to remove, immerse
in boiling water before applying the solvent. Do not use an abrasive.
Clean the diaphragm (3) with detergent or methylated spirit.
Replace components showing signs of wear or damage.
Reassemble the valve, making sure the metering needle (4) is in the cruciform
guides (5) and the diaphragm is seated correctly.
Fig.
6