I've had trouble getting any longevity out of reconditioned AEC water pumps (since the good old days when Lionel Moss used to do them).

SP Waterpumps reconditioned units have proved unreliable, I have had several, though saying that the firm has been as helpful as it can be, eventually supplying some new carbon seals so we can recondition our own.

The problem has been, I think, that the replaceable brass(?) top hat half of the seals have at some time had steel inserts fitted - which with low use in preserved vehicles have corroded and roughed up so the new carbons have lasted no-time-at-all.

The handbook says the top hat can be re-faced three times - but what were the dimensions of new ones? I've a worn brass one we've re-installed with a new carbon seal - which didn't last very long at all last time out, maybe 1,500 - 2,000 miles, I think because there isn't much meat left on it so the spring runs out of oomph when the carbon's only half worn. Anyway that's on the bus now.

We've made up a new top hat in brass and built up another pump - so I can carry a spare, my nerves are shot, this has been a long saga - but could only guess how proud from the casting it would have been when new. We'd like to make up more to the maker's original specification; so as well as that dimension would like to confirm we're using the right metal ...

Can anyone help?

My bus number (if any): RMA 65, RMA 62

Without access to new carbon seals I have done the following:

Order from John Crane seals an 87079067 mechanical seal. Then get the impeller machined so that the seal fits and have the machine shop seal it in place as required. The design of the seal is entirely different so it needs to be sealed. Get them also to make up a brass top hat bush to fit the body snugly. The rubbing face will need to be a mirror finish. Let the machine shop remove the old carbon seal so that the face protrusion can be checked against the travel of the new seal spring. The mechanical seal I have requires a bush to these dimensions:

overall height:0.494"
flange height: 0.177"
Major od :1.437"
minor od: 1.045"
id: 0.687"

You will need to check the shaft is not bent and have the impeller checked for run out once assembled to the taper of the shaft and fitted in the bearing, since it will act as a wobble plate and leak if not running true. You will probably need to have the housing clocked to ensure that the mating surface and bore for the top hat are parallel to the body 1/2 mounting face and/or at a right angle to one another. This operation will probably alter bush dimensions so the machine shop will have to measure the existing body and adjust as appropriate.

Having this done is only 1/4 of the required work. The bushes in the end caps will more than likely need to be renewed, that is if the shafts and gears are still serviceable. IIRC there are shims between the end caps and the housing to control the end float of the gears.

Do NOT use silicone sealant instead of a gasket to refit the pump to the engine, just as when fitting a PTO drive you will need to trial fit the pump to ensure that the intermediate gear and the engine timing gear have sensible backlash and adjust the gasket thickness if necessary. If you fail to do this and there is no backlash then the engine timing gears will be chewed up. It is common to find that previous overhauls have surface ground the mating face of the gear housing thus bringing the gears more closely into mesh. The mating surface of the seal and bush will require initial lubrication with grease as would the carbon seal.

This will cost a lot more money than originally thought.