MGB GT Water pump swap

The water pump on this car was making a terrible noise and there was an obvious spray line across and inside the bonnet in line with the pump bearing. A clear sign that its been leaking. I drained the coolant by disconnecting the bottom hose but I didn't drain the block- probably a mistake (see on)

First step was to loosen the alternator mounting bolts

 ...and the clamp bolt on the slotted strap bracket

 ...so that the alternator can be swung inwards and the old belt removed. This will be replaced.

The pullet is held on by 4 7/16 bolts with spring washers

 Once the 4 bolts are out the pulley comes off. I cleaned it up and resprayed it where the powder coat was coming off.

Remove to hose

The pump is held on by 4x 1/2 inch studs, 3 are the same length and one is longer. 

Unscrewing pump mounting bolts.

Long bolt next to new pump. The long bolt passes through the thickest point of the pump and so penetrates only as far into the block as the shorter bolts.

The long one goes through the widest  part of the pump. All bolts needed cleaning and the lower ones de-rusting! In addition the forward alternator hinge bolt passes through the pump and so has to be removed.

Front alternator hinge bolt must be removed to free the pump.

The old pump was removed, which is when I discovered I should have drained the block as there was more coolant to be released once the pump was off! Its gasket could then be pulled free. It wasn't in good condition

Old gasket was decidedly dodgy

New pump compared with old.

Refitting is as they say the reverse of dismantling. You need to clean all mating surfaces carefully so that the gasket can seal. I didn't encounter any problems.

Refit top and bottom hoses

Pump on- refit pulley and alternator belt- check and adjust belt tension.

Refilling with coolant has to be done in two stages: Add coolant to the overflow tank to at least half full. Remove the block top-up plug and fill with coolant to the base of the plug threads. Note that you have to fill slowly as the liquid has to find its way down. Fill and wait for it to settle then top up again... repeat.

Start the motor and run it until the top hose becomes hot, then stop the motor and repeat top-up as described above.