I just replaced the waterpump with a remanufactured wp. The reman wp appears to have a rough surface around the edge of the opening where the thermostat housing sits.

It is leaking slowly when the car runs.

How should I stop this? I have black rtv, should I use that? How would I go about smoothing out the surface if I can't use rtv?

 

RTV would be fine. There is a rubber gasket in there on the thermostate - it's possible the gasket is no good. Have you tried unbolting the thermo housing to see how this looks? That is probably your problem - either that or it just needs to be tightened down in general.

 

Well I tightened the 2 bolts down pretty good. I didn't quite check the thermostat's rubber though. I'll check that.

But the finish quality on the surface of the reman'ed waterpump was lousy. It didn't look smooth and machined, only rough and pitted. That's why I assumed it to be the culprit of the leak.