Waterpump

[Richard Webb]

How do I check which water pump I need to replace the old one? I have a Spitfire 1500 with a 1300 motor installed. Would it be the GWP200 or the GWP128? Two other questions. What is the best way to check the water pump is actually working correctly? And, what is the correct thermostat replacement, there are 3 different temperatures to choose from. Thank in advance.

[RobPearce]

The main difference in water pumps is the pulley. Early cars had a small pulley to match the small crank pulley (and dynamo) while later ones have larger crank and water pump pulleys (and a smaller one on the alternator). The other change was that some 1500s had a viscous fan, which has a different fitting on the pump pulley.

Does the car overheat? As in, boil and steam within a few minutes of running? If not, then your pump is working.

The lower two thermostats were originally "summer" and "winter" spec, but nobody bothers with that any more. The 88C stat is for 1500 engines and matches the 13PSI radiator cap. If you're on a 7PSI system, use the 82C stat.

[glang]

yes I reckon 99.9% of water pump failures are the internal seal leaking so water comes out of the tell-tale hole just behind the pulley (this is why the pump should be installed so the hole is in the lowest position).

This can happen if pump hasnt been used for a while so the seal faces have stuck and unfortunately, as the seals arent really replaceable, a complete new pump is required. 

[Richard Webb]

Thanks so far. No overheating problems as such. Just fitted a 21" radiator as old 16" was weeping a bit and in poor shape. Wanted to replace water pump as not sure what the age or condition is and just wanted piece of mind. Is not a viscous coupling and I have an new electric fan setup, could not use the old Kenlowe with the new radiator. So I take it the pumps are the same, thought it might be because looking at Rimmer Bro's, all the housings seem to have the same catalogue number. I can measure the pulley, but still don't know if it's a GPW200 or 128. I have a 13PSI radiator cap, so should I get the 88 deg. thermostat? Remembering this is a 1300 engine. Oh, and engine is not standard.

[glang]

The proofs in the pudding as they say, your set up isnt standard so run it and see where the temperature gauge settles when driving (you could measure the top hose temp with a thermometer to confirm its reading). Under half hotter thermo otherwise stick with standard. Youll have to set up the cut in temp of the fan as well (3/4 gauge?) while with the pump there's nothing more than keep an eye on that tell-tale....