D5B Hydraulic Pump Leak

My recently purchased and well used D6B has a leak at the hydraulic pump that appears to have been leaking (a drip about every 10 min when running) for a very long time. It seems to originate from the connection of the discharge hose. Somewhere along the way the discharge hose was modified and made shorter. I got a new hose made for the discharge and also replaced the hose segments on the suction hose. Reassembled with new o-rings and after a short run found it still to be leaking, apparently where the discharge line bolts to the pump. Next I got a new set of the "blocks" that hold the hose end against the pump and a new o-ring, drained the tank, reinstalled the hose with new blocks, new bolts, and a second new o-ring. It still leaks. The seating surface on the pump looks good, btw. I don't know why it leaks.

I should also mention there is also a fairly loud "whine" noise when the engine is running that comes from the pump. It loud enough to be noticeable but I don't know if it's normal or not. There is also a vibration in the the discharge hose but perhaps this is normal for a gear pump?

I thought of a couple of possible explanations but they are only guesses:

1. There could be a crack in the pump case into one of the bolt holes? I didn't see that but it would cause a leak like I see. Such a crack or even porosity in the casting might provide a leak path that is not visible from the outside.

2. Is it possible the pump is overpressuring the line? I don't know if there is a regulator in the system, but I would suspect there is, maybe inside the hydraulic tank. Anyway, no other connection on the system has a problem and the hydraulics operate just fine.

I'm checking pricing for a new pump. Looks to be about $800-$1000 with shipping. Some of those advertised don't show the manufacturer and I see China listed as origin on most. I'm curious if anyone recommends a good aftermarket pump.

I am attaching a few pics, some before and some after I worked on it.

These are "after" pics...

I ordered a new pump manufactured by a company called ITR. Website says the pump is manufactured in Italy. Comes with one year warranty. Should arrive in about 3 days. I hope this takes care of my leakage problem. I also hope I can get to the lower mounting bolt without needing to remove some other oil lines that impede access. We'll see.

ITR a a good company to deal with here in UK.
No problems with their parts

Thank you, Nicky 68a, I'm glad to hear a positive reference. I'm anxious to get the new pump installed and tested.

It's really frustrating when you have slow/tiny leaks you can't figure out.

Funnily enough,their rep dropped in today to drop some D8 ripper tips off and he told me that ITR now offer around 80% of Cat parts

Good to know!

I installed the new hydraulic pump today and I'm happy to report that I did a test run and saw no leaks. I also think I now know why I couldn't stop it from leaking earlier. On the old pump, the discharge port on the pump case is not centered in the bolt pattern for the hose connection. Apparently, that leaves the o-ring on the hose fitting offset so that it's too near the opening in the case to seal properly. I'm attaching some pics of the old and new pump and the finished installation. The numbers on the old pump case are my measurements from the edge of the bolt hole to the edge of the discharge port. The residue that was built up around the pump was a mess and it must have leaked from the time that pump was installed by a previous owner. New pump is also quieter than the old one.

On the first pic above the pump is out and you can see to the left of the oil filter where the pump will go. Below I am adding a pic of the finished installation.