My water pump failed on a recent trip back from Brooklands, luckily only a few miles from home. The ignition light also came on so at first I thought the fan belt had failed. However, once home, I discovered that the belt was still in place but the pulley was flopping about.
I removed the whole pump/fan/thermostat assembly (see details below) and discovered the pump impeller centre had collapsed and let the shaft locking pin fall out, loosening up the shaft and pulley (Figure 1).
I was lucky that the whole lot did not travel further forward and chew up the radiator. I later fished out a lump of moulded plastic from the header tank, which fitted perfectly over the broken impeller, so it had been “repaired” with this rather than replacing the impeller. Humpf!
The pump had been reconditioned during the car restoration and had only done 2,100 miles before failure. I sent the pump and a used spare off to EP Services for a complete rebuild. EPS supplied all new internal parts except the shaft and inlet donut – impeller, seal, Oilite internal bearing and a sealed outer bearing. They also checked and trued the pulley and centre taper. The cost per pump was £75 + tax & shipping. (Please note I have no connection with EPS, other than being a satisfied customer, see advert in TTT2.) The impeller supplied (Figure 2) was a much improved 6-vane angled design, rather than the original 4- vane straight design. This should give a faster smoother coolant flow, and so far seems to be excellent in service. It was interesting to note that my spare pump impeller looked like it would fail in a similar way if ever put back into service.
Other points of note in this exercise:
Fan – As I intend at some point to take the car to hotter climates, amongst other things, I fitted an MGB fan during the restoration. This is an excellent and hardly noticeable modification and really works well. It is easy to do and the parts required are shown in Figure 3. The original greaser extension was omitted to provide about one inch clearance between the MGB fan and the radiator, so the new sealed bearing solves the omission of the greasing capability.
Pump fixings – Brian Rainbow suggested recently that replacing the studs with bolts enabled the pump and hence the cylinder head to be removed without disturbing the radiator assembly. Well, having done this some time ago after a head gasket failure, I was able to remove the pump, fan, thermostat and top hose all as one assembly in under one hour. I just had to swing the dynamo outwards and undo the nearside radiator stay to give clearance. Replacement is just as easy, particularly pivoting the complete assembly on one bolt only, to align and fit the top hose. See Figure 3 for bolt details. Wonderful suggestion, thank you Brian!
The labels read:
Fan Bolts – All M5x0.9 pitch: 4 off 12mm thread length, with SS washers
O-ring – 25-30mm ID, 2mm thick (centres fan)
Pump bolts – M8x1.0 (fine), Hex 2x30mm thread length, Hex 1x50mm; Cap Head* 1x25mm
Washers – 4 spring lock washers
* This is fitted at the Offside upper stud location as spanner access is severely restricted. An hexagonal key or socket extension provides ample access for tightening and removal.
Pump lubrication – As both pumps only had a plain hole above the Oilite bearing, I sourced two flip-top oil lubricators and tapped the holes to M6 x 1.0, as for most of the MPJG engine bolting. NB. Only late TAs use oil here, as early ones used a greaser.
Ian Linton
