So in an effort to diagnose my cooling system leak on my GSL-SE, I bought a Stant ST-255 tester on ebay.



Once I had replaced the seal,the pump seems to work fine. But, either there is no check valve in the head (figure 1), or it isn't working, because the tester does not pressurize the system - all the pressure generated on the first stroke of the pump is sucked back into the pump on the backstroke.



I have a check valve (figure 2) included in the case but I can't find a way to attach it.



What is going on with this thing? am I missing parts? the third pic shows everything I got.

 

I'm guessing here, but does the valve go in the pump body before the hose?

 

No, it's made to fit into the radiator filler neck, and there's no way to secure it into the pump body.

 

Okay I shall now eat my words *munch munch* you were correct, upon unscrewing the pump barrel I found that the valve does in fact go in there. Thanks!



So I got my leaks diagnosed