installed Groco HF rebuild kit but pump leaks

[Hayden Watson]

Today I installed a full Groco HF rebuild kit because my 15 year old head did not prime any more. Now it pumps great but has a bad leak around the cover over the reed valves. I was probably too careful to not over tighten the screws on the plastic cover and it leaked at the center of the three screws on each side. I then tighten all 6 an 1/8 of a turn each using my best guess at good "star pattern" [center screw and then diagonal corner screws] until I just got the leak at both sides of the cover to stop. I was happy for at least 30 seconds which was how long it took me to notice that I now had a fast leak coming out of the bottom of the cover. I shut the thru=hull and loosened all screws to take the pressure off of the plastic.
I installed all of the parts dry except for a bit of plumbers grease on the seal on the pump plunger and stem.
Should a sealant like ATV be used?

 

[Peggie Hall HeadMistress]

I can't find "reed valves" in the parts list.. Groco HF instructions What's its real name and part #?

--Peggie

 

[Hayden Watson]

I can't find "reed valves" in the parts list.. Groco HF instructions What's its real name and part #?

--Peggie

The leak is at #10 HF-1 gasket. I installed it without any type of sealant. Parts #4 and #11 were clean and dry. I tightened the (6) #25 screws lightly with a screw driver initially out of concern about being too tight on the plastic parts. After installing there was a very small leak out both side near the center screw and I tightened those two screws but the leak was still there, so I tightened the four corner screws to the same as the center and then checked again. I kept repeating that process with 1/8-turn each time until the leak at the sides stopped. That is when I found the large leak at the bottom.

 

[Peggie Hall HeadMistress]

I think you need to give Groco a call...phone number is at the bottom of the HF instructions page.

--Peggie

 

[Hayden Watson]

Update:
I contacted Groco (ask for Pat) and he told me that this is a very common problem. The pump housing is made with a slight convex bow to the top and bottom mating surfaces and the cover is made completely flat. This lets the cover increase the pressure on the gasket at the top and bottom mating surfaces. Over time, the plastic cover takes up the shape of the pump base and becomes concave to match the curve of the base. When a new gasket is installed you do not get the additional pressure at the top and bottom because the both have the same curve.
The solution is to take a piece of 80 or 100 grit sandpaper on a flat surface and sand the cover until is it flat. After doing that, no more leaks and my HF is working perfectly.

 

[Peggie Hall HeadMistress]

That's great!!

--Peggie