Raw (water) deal
My BMC 2.2 engine has an overheating problem. I suspect it may be related to the water pump priming. I checked the weed traps and both were sealed with rubber sealant but I suspect there should be some sort of gasket. Could it be that the pump is not able to prime as air is coming into the system. How do I prime the pump?
IAN BUSTIN, via email
TONY REPLIES... You are correct, the caps on the sea inlets should be fitted with rubber seals, and as the pipework between the sea inlet and the brass raw water pump is normally all under suction, it is vital to ensure that there is no possibility of air leaks. Raw water pumps are normally self-priming, so if one will not self-prime, you have a problem. Look at the top of the thinner part of the body on your raw water pump (Jabsco). If it has a sort of ‘mini tin can’ stuck out of the top, this is a grease cap. Unscrew it and fill it with any easy to get grease. Give it a twist every day. If it still won’t prime, you might have a worn pump body.
Undo the ring of screws that hold the plate on the front of the pump. Then remove the impeller and inspect it. The ‘wings’ should have no splits at their base and the tips should be ‘rod’ shaped – not oval. It should not be covered in grease. Also inspect the pin that may be screwed through the impeller to allow the shaft to drive it. The inside of the front plate and the back of the pump should be flat with minimal grooving (my guess is that there are deep grooves in both).
Get hold of the shaft and try to ‘waggle’ it in the body. It should have only a tiny amount of movement.
Reassemble the pump using a new impeller and gasket if required. See if it will prime, if not, screw down the greaser while the engine is revving. If it then primes, the body is worn and a new pump is required.
If the face plate is grooved, it can be turned over, but I fear someone may have already done this.
For spares, try Cleghorne & Wearing or ASAP Supplies, but be aware that many older pumps are no longer obtainable. If so, think about using an electric pump fed from the ignition switch.