My 1992 580sk swing..

[JakeSherlock]

Hi there, I've just finished doing a bunch of work on my old backhoe including rebuilding my stabilizer and swing rams. Now I have an issue with the swing go figure. Yes the cam and bolt and pivot are all good and I have installed a new cam pivot bearing as well. Great! no more leaks but... now the swing drifts radically with any lean at all on the machine. I does function well and slows as expected and the end limits. With the machine running ,hands off controls, any lean and it drifts..quite badly and quite annoying. Now, also when the machine is parked say overnight and I push on the bucket (hoe in travel position) with my hands the hoe just swings over like it's completely disconnected from the swing cylinders..free floats like there's no fluid in the cylinders. It was fine before the repack. Having said this, the rod to the sequence valve moves freely and moves the valve freely. I have not messed with the sequence valve at all. Has some thing happened in that pesky valve to cause this? Should I be removing it and attempting a rebuild? Seems odd to me that this is occurring now.. Kinda like it has to be bled or something...Any Ideas?? I apologize for the long post...

 

[melben]

Sequencing valves are very trouble free on those hoes, my first thought considring the work done would be to recheck the rod packings in the cylinders, if not installed properly they are very easy to cut and your description indicates a very extreme leak and the fact that the problem did not occur till after the cylinder rebuild is suspicious

 

[JakeSherlock]

Hi Melben, thanks for taking the time...Respectfully, I have quite a number of cylinder rebuilds under my belt. I did search out and buy what I thought to be quality kits as I don't want to be redoing because of crappy bits. I did inspect the pistons and the bores closely while performing the work. Also I was very careful to exercise the rams slowly at idle after completion.. I'm not opposed to pulling them down again if I have to. I'm just wondering if there could be something other that could cause this. The sequence valve is indeed dry and not weeping. Some sort of air lock is not likely? very strange.

 

[JakeSherlock]

or a stuck relief somewhere.... I'm not too sure who posted it but I did read on here that someone had a number of problems with these sequence valves...but no detail

 

[JakeSherlock]

so as I wander around pruning...in order for this "neutral" scenario to occur wouldn't both cylinders have to have a problem? as they both work in unison .. one pulls while the other retracts. I can't possibly have made a boo boo on both...

 

[stinky64]

As Melben has suggested in numerous previous posts cycle your swing functions multiple times and check for heat in one or both of the cylinders which will indicate fluid blowing by a seal. No matter how many cylinders you have built before if you got a faulty kit there's no shame in a redo, it just sucks...The worst part about faulty parts is second guessing your work when you know for a fact that your efforts were spot on but unfortunately it happens..

 

[JakeSherlock]

Thanks for your remarks. Everything I know I've learned the hard way . 60 yrs old now with two red seal trades and 44 years of tying up boots. Perhaps you'll be kind enough to put some links here regarding melben's numerous posts ?

 

[skyking1]

please correct me if I have it wrong, but as I see it, a cut in one packing would do it as both cylinders are acted on on opposite sides. One leak would do the trick and the heating thing sounds like an easy check. you could even shoot it with one of those infrared laser thermometers.

 

[Tinkerer]

Did you remove the swing cylinders when you resealed them ?
If the boom swings as freely as you describe it seems to me it isn't a bad packing.
A lot of oil has to move for a boom to swing that fast.

 

[Welder Dave]

Could still be air in the system. I'm not sure but doesn't the swing have less flow than the other cylinders to slow it down? If so might take more back and forth to bleed all the air. My hoe uses a rotary cylinder but the lines to it are 1/2 the size of the other lines. Another thing you could check is how much swing power you have. Low swing power might point to leaking cylinder packing.

 

[alrman]

Is the cushioning at the end of the cycle EXACTLY the same on each side.
It only takes a very small amount of adjustment for those valves to play up.

 

[stinky64]

Sorry Jake but I'm not that computer smart, I can fix the hydraulics but not the computer

 

[JakeSherlock]

Thanks a lot to all you guys taking time to jibber about my issue. I always tell guys at work I don't have answers, .I only have ideas. I can't fix my computer either lol. So,yes I do agree that one cylinder could cause a drift in theory but I have to agree with tinkerer here.. a lot of oil has to move to create a free swing condition like this. No , I did not in fact remove the swing cylinders. Should I have ? Seemed like unnecessary work to me. It's almost like one or both are slowly draining after sitting. alrman, I have not played with the adjustment of the valve rod yet and I couldn't swear that the damping is totally equal at either end of the stroke.... seems close from the seat. It seems to me that the function of the cam and rod is just to dump oil as the cam bearing and rod activate the plunger in the valve. I don't think this is all the valve does though. I've looked at the exploded view in my parts manual and a "drain" tube is listed...3 of them depending on your valve bank configuration. Now , there is the swing valve in the bank and the sequence valve and the cam and pivot for travel dampening and the drain tube connection. Can someone try and explain exacting how this set up works? It's a bit of a head scratcher for me! Thanks a lot for any and all replies.

 

[Tinkerer]

I asked about removing the cylinders so that we would know if the hoses were reconnected wrong.
No there is hardly ever a need to remove swing cylinders to reseal them.
Do you have or need the service manual for your SK ?

 

[JakeSherlock]

many years ago I had to learn how the double tilt cylinder set up worked on a Cat D6C from the early 70's. There were flow directing one way check valves that had been chucked out during a replumb on the blade. Nobody realized how the set up worked. I didn't know what these check valves were at the time and neither did the 2! ...yes 2.. mechanics that hucked em out. I needed that old Cat years later up on a road building job and I needed that tilt working! It took a lot of reading and routing around on the web to figure it out ( in the old days you went to the library or the old guy down the road) Lots of single tilt systems... not so many dual cylinder set ups. This kind of reminds of that...reciprocating cylinders.. tube end vs rod end volumes and stuff.....

 

[JakeSherlock]

Thanks Tinkerer for that clarification. I do have a service manual on my computer. Is this info in it? Have I completely lost it?? lol

 

[JakeSherlock]

Ok ,so I went back to my service manual to the sequence valve section and I have been in there before and now realize again that the short coming here is a lack of theory of operation. I did look for a kit and I read on the forum of a connection to find one. I could definitely do a rebuild on the valve using the manual but cannot seem to figure of the operation of the system it's a part of...

 

[JakeSherlock]

figure out .... that should read

 

[Tinkerer]

You said all was well until you resealed the cylinders.
I wouldn't disturb the swing sequence valve.

 

[JakeSherlock]

Yes this is a true statement, although I did Pull the top boom pin and weld and resurface it for wear, install a fresh alignment bolt, pull and repack the pivot and install a new cam bearing. I did not loosen the jam nuts nor adjust the link from the pivot to the valve at all. As it wasn't damp at all I thought why go there. Also I did check the rod and valve to make sure all was free. So yes, confounding. When I discovered this issue I was just wiggling the boom looking over wear. It swings over freely and then comes up hard part way over...like the piston coming up against fluid...and then it goes tight like one would expect until it sits for a while and then same thing. Hence my comment above regarding relief.