403 Water Pump
 

Are these easy to take off and service? Ran the engine up and noticed a small stream of coolant running down the water pipe from under the pump/ thermostat

Peter,
It sounds like the seal in your pump is defective.
The pump will need a rebuild or if badly corroded, it will be best to replace it .
You need a puller and press to rebuild it .

The easy part of the process is the removal and refitting of the pump

Geoff

I know that INRacing in Nottingham (Engineering and Machining - INRacing) will recondition Bristol water pumps, though it's quite expensive. I believe they can also supply new impellers, if you want to be really thorough.
They charged me £250 + VAT.

peter,
your pump may be rebuilt using a new carbon-ceramic seal. This involves machining a new seat for the carrier of the carbon disc. The ceramic part is mounted on the impeller (see photos). So the important point is that there should not be significant corrosion in the bore which prevents machining a new seat. You cannot ascertain this until you take the pump apart and remove the old seal. BOCA spares I think provides an exchange service or can supply a new pump ready for you to use if you have no machining facility. Ask Julian Caples.
sincerely,
vincent chai

Vincent
You forgot to mention that BOCA Spares are only available to Full Members of BOCA .

Note
I don't use the ceramic seat and prefer the seal to run directly on the impellor.

Geoff

Geoff,
The carbon disc - cast iron (impeller) seal has stood the test of time. I must have been thinking of the BOCA bronze impeller which is used with the ceramic disc.
sincerely,
vincent

Finally got to look at it this weekend. Judging from the movement at the fan end of the shaft I am surprised the mechanic fitted it without query. But then he didn't do up the petrol feed bolts or my front exhaust to the manifold either. Must have been a work experience lad.

Just to make things interesting the top bolt (by the termostat) won't budge and has rounded. I can't find a socket which will fit. I've tried 5/16 bsf (fitted all the other bolts), 1/2 UF, 13 mm and 12 mm. They either turn or will not fit.

S P pumps Warrington almost while you
wait,2 hours, did a Bentley pump for me £110

Finally got the pump off (well, my welder did!) and took it to a local 'reliable' engineer Water Pumps - Vintage, Veteran & Classic Water Pumps - UK
Cost £200 plus Vat but he had a lot of trouble getting the pully and impeller of. He said Bristol were very thorough!

The old bearing is hand pressure seized.

The offending top bolt was virtually seized into the block by corrosion. Now to refit with new ss bolts and plenty of anti corrosion fluid. A non standard part are studs in place of the two lower bolts with W/W nuts.