The cooling system consists of a water jacket around the two cylinders in each of the cylinder blocks. A large brass radiator is installed at the front of the appliance, and a large fan fitted behind the radiator induces a draft.

The water is pumped around by a centrifugal pump from the bottom of the radiator to the top of the front cylinder block, to the rear cylinder block and back into the top of the radiator.

In order to prevent the engine from overheating while pumping a feed from the main water pump is used. On early models this flows through a copper coil in the oil tank to cool the oil and then into the radiator. Later models also had a direct feed to the radiator so cooling could be supplied without feeding water through the oil tank in case it should leak.

Tightening the Water Pump Gland

  1. Open off side of the bonnet.
  2. Tighten the water pump gland through the hole in the bracket between the pump and the timing case using the special water pump gland nut tool (Do not overtighten).

In the event that this does not reduce the leak it will be necessary to replace the gland packing.

Repacking the Water Pump Gland

  1. Remove small water pipe joining pump to inlet manifold.
  2. Remove the jubilee clip securing the flexible pipe to the pump.
  3. Loosen the water pump gland using the special tool
  4. Remove the two bolts securing the upper pipe to the water pump.
  5. Remove the three nuts holding the aluminium water pump bracket to the timing case.
  6. Withdraw the pump including driving gear from the timing case.
  7. Remove the two dome nuts securing the pump input water fitting to the pump and remove this fitting.
  8. Remove the six bolts holding the back face of the pump on, and remove this face.
  9. Remove the locking nut on the impeller
  10. Remove the impeller using the special tool.
  11. Remove the three bolts holding on the aluminium pump bracket and remove the bracket.
  12. Withdraw the pump shaft.

Cut new gland material from the PTFE rope, it is easiest to refit this using a pipe fed through the pump where the shaft was and packing the rope around this, the shaft can then be slid into the pump more easily.

Reassembly is the reversal of removal.

Removing the Radiator

  1. Remove pump feed pipe, two feeds to water pump, feed from pots
  2. Remove brass rail and headlamps at chassis rails.
  3. Remove starting handle (hammer out three taper pins and slide off shaft.
  4. Unbolt starting handle boss where it fits the crankcase.
  5. Support radiator with the jack using a large piece of wood to spread the load.
  6. Unbolt and remove radiator supports.
  7. Lower the radiator on the jack.
  8. Lean radiator back and withdraw the starting handle boss. This may require some jiggling.
  9. Raise the radiator carefully on the jack (if it snags you wont be able to tell, causing it serious damage).
  10. Lift the radiator off the jack and store safely