Ok so im getting ready to put this thing back together and toss it in the car, and Im wondering which water pump to use. Does anyone know if the 20B unit has more capacity than the 13B? and what the hell is the vacuum thing on top of the t-stat housing?

Thanks
Pat

 

Been told the 13b is a better water pump.

 

the 20b has a dual thermostat setup. it normally runs just from the front thermostat which is hotter (wanna say 92c), and under certain conditions it can open the second colder (82c same as the s5 fc/fd), stat. theres a sensor, and solenoid to switch the thing.

ive seen 4-6 of these things and 5 of em were bad, on mine i cut it off and put the radiator cap there.

the 20b water pump probably flows more, although if it fails its around $500, and its gotta come from japan, so its 6-8 weeks away.

the fc/fd setups are cheaper, and much more available

 

thats what I plan on doing with mine and theres one less sensor and solenoid to put back on. + like said above the 13b pump is better anyways.

 

I have the 13B pump on mine. I would recommend using the stock pulley size and not going with an underdrive pulley as this will likely cause some overheat issues. Also, I would recommend a tensioner pulley to make sure you get enough back-side ride out of your belt since the airpump will no longer be there to perform that function. As mentioned above, you also get to avoid needing more sensors/solenoids, etc by avoiding the 20B twin thermostat setup.

Aaron