Grundfos Scala 2 dismantle, repair, and reassembly 

Take off the shroud to get a better look at where the leak might be coming from. Could be the main shaft seal, but could be a cracked housing.

www.supplyhouse.com/Grundfos-99016047-Connection-Module?Shopping_ntm&Shopping_NTM_New_users&gad_source=1&gclid=Cj0KCQiAn-2tBhDVARIsAGmStVlnBZ7SuuXiXyPD2RsrkK7e7j5RJ3QNC-Looe7Q0DMZ7Q_Zs0a2pKMaAs8aEALw_wcB

I’ve seen a few of these pumps with this problem, cracking at the prime port due to over tightening, don’t use thread tape or paste.

Just want to add that these pumps are notorious for leaks and not just at the prime plug. I have witnessed the failures many times now. Conveniently warranteed at just 2 years , users are S.O.L. with their failing pumps after that period. A real embarrassment for an otherwise great company.

Make sure it’s at 18psi check it at the air valve and fill it with an air compressor at the valve

Grundfos recommends the air charge be 70% of desired working pressure. Its a typical Schrader (tire) fill valve.

Grundfos repair kit 99016047

So your saying it continually runs even when the water discharge side is turned off? Sounds like a bad check valve. Take out the water inlet spring and seal and make sure it is clean and free of debris. Also take out the spring and check valve out if the top prime port make sure it is clean and free of debris.