Valve screeching

rjmack · Nov 10, 2010

I think the valve is pretty much the highest point in the system. Why? What would that do?

i was thinking that, if your pump is cavitating or if there is some other source of air in the system, shortening the hoses and running 90* fittings would allow air to bleed to the valve when the machine was sitting.

sometimes, especially when its cold, it can take a long time for air bubbles to separate out. the system on my snowplow is such that i can see through the filler cap where the oil returns to the reservoir (high point) and once i have run the system low enough to cavitate i can see that the bubbles get so small and disperse so widely that the oil almost looks like an emulsion. when the oil is in that condition, the lift cycle is noisy and when it hits the relief it just screams. it can take overnight to settle out.

with the current hose arrangement to your chute adjusting cylinder it looks like there are two spots where the air would pool in the lines.

KWentling · Nov 10, 2010

So now we know that we don't know what the original operating pressure was. I would seriously doubt that it was over 2000 and probably more like 1500 because most older tractors wouldn't have had the pressure to operate it if it was over 2000. I'm going to assume that the remotes on the tractor have been working normally in other applications so we can eliminate that as a problem. Is this squealing coming from the valve that operates the blower or the tractor's pressure relief valve? It's not coming from the cylinder itself (internal leak in the cylinder)? Do you know what the tractor's operating pressure is? You have verified that the tractors oil level is good? Are the hoses new. If old, maybe the inner rubber lining has flap restricting the flow. Seen that before. I can't see air being the problem because hydraulics are self bleeding. If you have fully stroked the cylinder a few times and at the end of the stroke the relief valve has opened (squealed) the system is free of air. Even if the oil was being aerated and the air settled out in a hose, it would quickly be purged when the cylinder reaches the end of its stroke. Even if the air remained trapped somewhere, it would just make the operation spongy. Taking the cylinder off and checking its operation with no load is a good idea. I think it just a poorly designed system that may have worked OK when new with everything clean and tight and now that it is old and worn it getting bound up. Have you tried adjusting the tension of the cable? Tighter or looser make any difference? About out of ideas here.

Kenny! are you lurking here somewhere? Any ideas?

Kim

KWentling · Nov 10, 2010

Had another thought. I wonder if there could be a built in flow restriction to slow the cylinder down. It would likely be in one of the cylinder ports if factory. Otherwise it could be in a hose fitting. If you feather the control valve, does it still squeal? I've been assuming that the squealing while moving is when the cylinder is retracting? Is that correct? A cylinder can push more than it can pull.

Kim

Jay4200 · Nov 10, 2010

I'll be sure to let the thing run and cycle everything a few times to purge the air. As I said, I just finished hooking stuff up, so there is/was definitely air in the system in various places. The squeal is in both directions on the chute throughout the travel and only at the stops on the flapper. The squeal is most definitely coming from the new remote valve.

The entire remote setup is new, so there was no 'before' experience. The previous setup was just the pair of PB/tank QC fittings (now residing on the outside of the ROPS) that ran my backhoe. The PB line comes from the loader - I had to move a QC up front to swap the loader PB from the 3pt to the rear line, so the 3pt was disabled when I ran the backhoe.

With this new setup, I keep the loader PB connected to the rear line, which in turn runs to the remote valve 'IN' port, and the 'OUT' port connects to the old rear tank line. These are the two female QC connections attached at the ROPS. I then ran a new PB line that goes from the remote valve PB (via male QC) to the 3pt connection up front (that hose is zip tied to the ROPS above the QCs in the pics). When the blower is removed, I plug the new line into the PB QC to run the 3pt, and leave the new line disconnected for running the backhoe.

JayC

Gary Sweat · Nov 10, 2010

Jay4200 said:
I'll be sure to let the thing run and cycle everything a few times to purge the air. As I said, I just finished hooking stuff up, so there is/was definitely air in the system in various places. The squeal is in both directions on the chute throughout the travel and only at the stops on the flapper. The squeal is most definitely coming from the new remote valve.

The entire remote setup is new, so there was no 'before' experience. The previous setup was just the pair of PB/tank QC fittings (now residing on the outside of the ROPS) that ran my backhoe. The PB line comes from the loader - I had to move a QC up front to swap the loader PB from the 3pt to the rear line, so the 3pt was disabled when I ran the backhoe.

With this new setup, I keep the loader PB connected to the rear line, which in turn runs to the remote valve 'IN' port, and the 'OUT' port connects to the old rear tank line. These are the two female QC connections attached at the ROPS. I then ran a new PB line that goes from the remote valve PB (via male QC) to the 3pt connection up front (that hose is zip tied to the ROPS above the QCs in the pics). When the blower is removed, I plug the new line into the PB QC to run the 3pt, and leave the new line disconnected for running the backhoe.

JayC

I'm not very familiar with QC's but is it possible that one of them is not fully open when connected?

Jay4200 · Nov 10, 2010

Gary Sweat said:
I'm not very familiar with QC's but is it possible that one of them is not fully open when connected?

I don't know - seems unlikely, but I'm not very familiar with QC's either.

JayC

KWentling · Nov 10, 2010

I went back and read the whole thread again. Not sure where I came up with it moving one way OK and squealing the other. Since it has enough pressure to operate the chute rotation but goes over the PRV doing it, both ways, that tells me there is a restriction. I think if you were to take the hoses off the cylinder, you would find a flow restriction somewhere, probably at the rod end port. They would put the restriction in to slow the cylinder down so it wouldn't rotate the chute too fast. The restriction would cause back pressure. Say the flow from the tractor's remote is 3 GPM, but the restriction will only allow 1 GPM through. The other 2GPM has to go somewhere. That somewhere would be past the PRV. I would expect that if the cylinder was off the blower, it would still squeal the PRV. Feathering the valve lever (reducing the flow) might reduce or eliminate the squeal. Even if you were to tighten the PRV down tight it would only shift the squeal to the loader valve's PRV. I think it is probably operating as designed. If there is the built in restriction, and you can't live with the squeal, you could plumb in an adjustable flow control to limit the flow to the valve and bypass the rest to sump.

Kim

Jay4200 · Nov 15, 2010

KWentling said:
Since it has enough pressure to operate the chute rotation but goes over the PRV doing it, both ways, that tells me there is a restriction.

This is the chute rotation cylinder - it appears to have an unnecessary fitting on it (right side) - maybe a DIY flow restrictor?:

The flapper cylinder has a 90 on it that might also serve to do the same thing - no resistance so no squealing ('till I hit the stops), however:

I've gotten everything together now, and can operate the chute cylinder squeal-free by feathering the valve, but it's not super-easy. The chute seems to be freeing up slowly as the lube works into it and the rough edges wear off. I'm working on a plan to re-engineer the chute mount and get it running on bearings like it should in the first place. Project for another day:

JayC

KWentling · Nov 16, 2010

The fitting in question is just a swivel adapter. I've added restriction by tapping the crimp on fitting on a hose end and screwing in a set screw with a small hole drilled in it. Something like that is what I expect you would find if you were to take the hoses off the cylinder. I would just ignore the squealing and run it the way it is. You won't be operating the chute enough to heat the oil or do any harm to the hydraulics. Maybe you could rig up stops that would contact the lever and limit its travel to a point that prevents the squeal. You could use bolts and locknuts so it would be adjustable.

Kim