Water pumps

[944cabby]

I've been looking at water pumps on the PET cd tonight for the S2 as i'll get mine changed on the next belt change.
Now i thought that the 968,S2 and 2.7L '44 all shared the same pump (mine's on it's second pump and has 2.7 visible on it) but on PET they all have different part numbers.
Are they all interchangeable?
Also does the 944T pump fit if the additional small thermostat is removed?

 

[TTM]

There are two kinds of water pumps, the one for the 100 mm bore block has a 68 mm large impeller and the one for the 104 mm bore block (as found on 2.7, S2 and 968) has a 78 mm impeller. I have no idea why Porsche use a different part number for the 968 water pump but physically it is still the same as the 2.7 & S2's. Perhaps they just fancy tracing for what kind of model they sell parts for. The supplier that makes water pumps is Laso ; you can check their catalogue [link=http://www.laso.de/pdf/LASO%20PKW%20Gesamtkatalog%202009.zip]here[/link]. You may not want to fit the water pump with the smaller impeller (all 2.5 engines, including turbo) as it may not flow enough for the 104mm bore block that contains half as less coolant as the 100mm bore block (0.55L against 1.1L). PS : in case you were considering replacing the thermostat don't fit the one from Laso, it's rubbish, I had problems with mine on the S2 (doesn't open wide enough, too many wires on the spring). Stick with the 83°C unit from Wahler which is likely to be the one already in your current waterpump.