County vs. Hobourn Oil Pumps

[dasadrew]

Have just spent a week trying to track down an annoying oil leak from the oil pump / transfer housing area. After nipping up all bolts, nuts and screws it still kept seeping. Seems to be coming out of the relief valve plunger area.

Had no choice but to take the oil pump off the car now. Have just disassembled it and uncovered a tale of why not to pick 'n mix!

My original oil pump was shot and I bought a County replacement. Not being very impressed with the machining on the County parts and being somewhat sceptical regarding the spring (which has been discussed on some other threads), I decided to to make a Frankenpump out of the best of both, using the County body and rotors and the Hobourn relief valve parts.

I guess I should have noticed that the Hobourn relief valve plunger cap had its "O" ring groove at the bottom and the County cap had it at the top.
I guess I should have noticed that the County holes for the retaining split pin were positioned differently to the Hobourn ones.

Oh well, ignorance of youth and all that. Rather belatedly I've now determined that the "O" ring groove in my Frankenpump is actually partially outside the cylinder bore against which the "O" ring should be sealing. Dohhhhh! The only silver lining in this tale is that I'd double ordered a set of oil pump seals those few years back and so I can get right back on to the case tomorrow after work!

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[SaskStag]

That explains a lot......

Had a lot of seal problems too

[Gkm24]

Mines brand new and leaking already. Car has only been running for 30 minutes!!

[Stag therapy]

I did so much swapping and changing when I had no oil pressure when I came to restart my engine as part of the rebuild, that I realised I had at one time built what you call a Frankenpump. Principally because once I had pressure, there was an oil leak from the pump.
A small comfort to know there are others who made similar assumptions about seemingly interchangeable parts.

[flying farmer]

Mines brand new and leaking already. Car has only been running for 30 minutes!!

Here is a picture of a brand new county pump from a couple of years ago, just how it came out of the box.

Note the sliver of O ring poking out of the pressure relief valve.

I was going to remove the valve anyway to fit an original spring, but if I had fitted it as it was delivered I would have had to strip it later as it would have leaked with damage like that!
Neil
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[dasadrew]

The machining on those County pumps is atrocious. When I now looked in detail, none of the edges have been deburred and the bore where Neils "O" ring has been sliced was really rough on the surface. I've now used some fine wet-or-dry to get the surface smooth where the "O" ring sits. The old adage seems always to hold up "If at all possible refurbish and refit the original parts!"

Drew

[jbuckl]

Also had all this shizzle before.

IIRC i posted my findings / frustrations at the time.

if you are lucky, you get to see the o-ring sliver before per neils picture

FWIW, buy the hobourn pumps when you see them at auto jumbles, even though hobourn were pretty poor, they were a 'county mile' better then the others

[Hughesy]

Has anyone checked the diameter of the relief valve in both pump types? I am getting a very slight increased diameter on the County pump. My Hobourn pump's relief valve is showing some wear (looks like polishing) in a couple of places. Both valves are a loose fit and interchangeable. My have a spare new County pump so I am thinking to swap the relief valves. Craig