Bobcat 610 valve body keeps leaking with new seal...

[Bpu699]

Well, still working on the craigslist bobcat 610 I bought. What was supposed to be easy has led to about 10 weekends of work...sigh. Got everything to work, no sprung a leak from the valve body main lift spool.... Leaks where it attaches to the Clovis arm for the pedals. Didn’t leak at all until I used a bunch of brake cleaner to spray down the valve body. Figured it ate up the seal? Per schematic only 1 seal at that end. Went and bought the seal, or more accurately a pack of 5, as that’s how they were sold. Taking out the spool and seal was pretty uneventful. Unscrewed the cap under the bobcat. Pushed the spool out, it did take some tapping but not a lot of force. Old seal looked fine, but sealing lip was slightly chewed up... Schematic says there a seal at the back that’s identical, I don’t see any such seal unless it’s deep inside. Either way, wasn’t leaking at the back by the screw cap. Replaced the seal at the front. Spool looked good, perhaps a couple tiny specks of pitting. Very gently polished the spool end sticking out with some fine 500 wet/dry . Did this for about 3-5 seconds, very light. Didn’t polish the hard chromed area. Put it back together...leaks 5x worse. Took the thing back apart, figured I damaged the seal. Turns out I did, had a tiny nick. Placed new seal. Going up...no issues, going down, leaks, still more than before I started... Now, it’s possible I damaged 2 seals, but unlikely. Is there a trick to this??? Am I missing something? Something internal I’m supposed to do? Did I damage something internally removing the spool? I doubt it, as there really wasn’t much force needed. Could an internal seal be leaking causing pressure to come out the front? I’m lost, to me it looks like there’s just the front seal, and that it?? That little front seal can’t really hold back 1000psi, or does it?

 

[flyerdan]

The only thing I can think of is there might be a burr in the bore that's taking out the seal, should be easy to tell with the rag or finger test.
In the manual thread somewhere, there's a book for Melroe Control Valves that covers rebuilding and testing these.

 

[Bpu699]

The only thing I can think of is there might be a burr in the bore that's taking out the seal, should be easy to tell with the rag or finger test.
In the manual thread somewhere, there's a book for Melroe Control Valves that covers rebuilding and testing these.

Thanks... I didn't feel any burrs, will recheck. Its really odd... Was also thinking perhaps the spool isn't perfectly straight? But then it wouldnt slide in I would think... Sigh...

 

[Bpu699]

The only thing I can think of is there might be a burr in the bore that's taking out the seal, should be easy to tell with the rag or finger test.
In the manual thread somewhere, there's a book for Melroe Control Valves that covers rebuilding and testing these.

Alright, never seen this before... oil leak is from the metal shaft itself, not the seal! The shaft is machined stainless steel. Then they plug one end with a machined eyelet made of regular steal. So, the shaft isn’t one piece. Rather, it’s 2-3 pieces! Not sure why they did that or used different types of steel... Where the plug fits (machine fit) it leaking at the insertion seam!!! Anyone ever pulled this plug out, sealed with sleeve retainer like loctite 640, and put back in? I’m worried about applying a lot of heat or force as I don’t want to damage the shaft itself...it looks like part of it is brazed on? Any help appreciated...

 

[Bpu699]

Alright, never seen this before... oil leak is from the metal shaft itself, not the seal! The shaft is machined stainless steel. Then they plug one end with a machined eyelet made of regular steal. So, the shaft isn’t one piece. Rather, it’s 2-3 pieces! Not sure why they did that or used different types of steel... Where the plug fits (machine fit) it leaking at the insertion seam!!! Anyone ever pulled this plug out, sealed with sleeve retainer like loctite 640, and put back in? I’m worried about applying a lot of heat or force as I don’t want to damage the shaft itself...it looks like part of it is brazed on? Any help appreciated...

Fixed it, in case this helps anyone. Dipped the part in acetone to clean it, left for several hours. Got some anareobic loctite 640 (bushing adhesive) and wicked it in between the pressed parts. Also made up a contraption using 1 inch radiator hose slipped over it to the end to force the sealant under 50 psi into the microscopic gap. Cure 24 hours, wipe off excess. Worked great, no leaks between the pressed parts.