630 Screeching in lift arms and bucket hydraulics

[discountufoparts]

I have a new interesting development. My lift arms and bucket tilt are screeching whenever I do anything. Was patching up some plow truck ruts during the warm spell we are having and it came on pretty fast. I notice a drop in charge pressure as well whenever I drop or lift the arms now from about 180 to 110 pds of charge. I don't have a pressure gauge for the hydraulic circuit just the charge circuit as that is where most of my problems have been in the past. I plan on draining the fluid and checking the filter in the metering block for a blockage there. Just wondering if anyone knows if that loud reverberating screech in the hydraulics is a blockage, the relief valve, or something more ominous. Pump has about 15 hours on it from LPS.com All filters were new at that point as well as all new fluid. New rebuilt hydrostat and drives. No problems with hydrostat system at all. Thanks.

 

[OldMachinist]

Might be a restriction on the inlet to the pump. I think the last time a member had something like this he found part of a rag in the hydraulic tank blocking the outlet.

 

[discountufoparts]

Might be a restriction on the inlet to the pump. I think the last time a member had something like this he found part of a rag in the hydraulic tank blocking the outlet.

I will have to look for that to when I take it apart on Wednesday.

 

[discountufoparts]

I will have to look for that to when I take it apart on Wednesday.

I checked everything today except for relief pressure as i did not have a quick connect to hook to the aux connectors. I was wondering if anyone knows on the relief valve on the valve bank, should i be able to easily manipulate that valves relief plunger by hand with little to no resistance. Also if it is any help, the adjustment seems to be adjusted all the way in with no more adjustment left. It can be backed off however. I took it out to clean it and noticed it seemed like it had no pressure on the spring.

 

[discountufoparts]

I checked everything today except for relief pressure as i did not have a quick connect to hook to the aux connectors. I was wondering if anyone knows on the relief valve on the valve bank, should i be able to easily manipulate that valves relief plunger by hand with little to no resistance. Also if it is any help, the adjustment seems to be adjusted all the way in with no more adjustment left. It can be backed off however. I took it out to clean it and noticed it seemed like it had no pressure on the spring.

I checked the pressure at the auxiliary connectors and while it will build only to 1800 psi the blow off starts blowing off at like 900 psi. NoW I thought relief valves were supposed to start blowing off at ten percent of maximum pressure. Does anyone know if the bobcat relief is supposed to start blowing off at 50% of maximum pressure?

 

[Tazza]

I checked the pressure at the auxiliary connectors and while it will build only to 1800 psi the blow off starts blowing off at like 900 psi. NoW I thought relief valves were supposed to start blowing off at ten percent of maximum pressure. Does anyone know if the bobcat relief is supposed to start blowing off at 50% of maximum pressure?

It shouldn't open till it hits the set pressure, not before.
Pull the relief out and see if it has stuff stuck under the seat or has a broken spring.

 

[discountufoparts]

It shouldn't open till it hits the set pressure, not before.
Pull the relief out and see if it has stuff stuck under the seat or has a broken spring.

I pulled it out and cleaned it but didn't really see much in it and didn't notice the spring being broken just extremely weak.

 

[Tazza]

I pulled it out and cleaned it but didn't really see much in it and didn't notice the spring being broken just extremely weak.

If it is an adjustable one, screw it in a bit more to increase the pressure. Some are adjustable, the others use shims.

 

[discountufoparts]

If it is an adjustable one, screw it in a bit more to increase the pressure. Some are adjustable, the others use shims.

It was a screw in type but it looked like it had been cranked in completely by the previous owner. There is no more adjustment left in it. I can easily push the valve in with little effort.

 

[OldMachinist]

It was a screw in type but it looked like it had been cranked in completely by the previous owner. There is no more adjustment left in it. I can easily push the valve in with little effort.

Sounds like its time for a new relief valve.

 

[discountufoparts]

Sounds like its time for a new relief valve.

I think I need to start an auction of one of my kidneys to pay for that new relief valve at 342 dollars plus 26 dollars shipping and handling.

 

[Tazza]

I think I need to start an auction of one of my kidneys to pay for that new relief valve at 342 dollars plus 26 dollars shipping and handling.

Ouch, that is a lot more than i would have expected....
If you haven't ordered it, you could try taking it to a hydraulic supply shop, they may have something that will do the job and mean you don't need to sell a kidney

 

[discountufoparts]

Ouch, that is a lot more than i would have expected....
If you haven't ordered it, you could try taking it to a hydraulic supply shop, they may have something that will do the job and mean you don't need to sell a kidney

The plot thickens....
So I put in the brand new relief valve in place of the old relief valve. A very easy task by the way. Took about 45 minutes all tolled up. Fixed screeches on up and down on auxiliary hydraulics, main boom and down of bucket tilt but.........
Screech is now worse on tilt up of bucket. I have rebuilt this ram before. Is it possible this ram is bad once again? If my pins were jamming, they do have about 1/4" to 3/8" slop, side to side play not up and down, all around on the bucket tilt, wouldn't I have an issue both up and down or is there another possibility? I don't seem to hear the ram screeching but it sounds like it is coming from the steel limes on the main boom that come from the bucket cylinder.

 

[jerry]

The plot thickens....
So I put in the brand new relief valve in place of the old relief valve. A very easy task by the way. Took about 45 minutes all tolled up. Fixed screeches on up and down on auxiliary hydraulics, main boom and down of bucket tilt but.........
Screech is now worse on tilt up of bucket. I have rebuilt this ram before. Is it possible this ram is bad once again? If my pins were jamming, they do have about 1/4" to 3/8" slop, side to side play not up and down, all around on the bucket tilt, wouldn't I have an issue both up and down or is there another possibility? I don't seem to hear the ram screeching but it sounds like it is coming from the steel limes on the main boom that come from the bucket cylinder.

When you rebuilt the bucket ram did you check the rod for straightness? Those bobcat single tilt cylinders seem to get bent often and then bind in the gland. Although it is a aluminum gland and should not make that noise check it anyhow. They can be straightened in a press.

 

[Tazza]

When you rebuilt the bucket ram did you check the rod for straightness? Those bobcat single tilt cylinders seem to get bent often and then bind in the gland. Although it is a aluminum gland and should not make that noise check it anyhow. They can be straightened in a press.

By screech, could it be from air bubbles in the oil? It may be still bleeding them out?
There is a chance it is a bent rod, they don't bend often, the tilt ram is more prone to bending.

 

[discountufoparts]

By screech, could it be from air bubbles in the oil? It may be still bleeding them out?
There is a chance it is a bent rod, they don't bend often, the tilt ram is more prone to bending.

It is a tilt ram cuircut that is screeching, but only in the tilt up position. It is so loud it is rattling the entire circuit and I can not hear the exact source. Also since I have posted it on about 1 out of 25 or so tilt ups it is not as loud.
We did check the ram last time we repacked it but the last time I repacked it I had not been using the digging arm as much as i had been so there is a chance it could have bent a little. I will order a seal kit for it and see if that fixes it.
The oddest thing is the one direction only.

 

[discountufoparts]

It is a tilt ram cuircut that is screeching, but only in the tilt up position. It is so loud it is rattling the entire circuit and I can not hear the exact source. Also since I have posted it on about 1 out of 25 or so tilt ups it is not as loud.
We did check the ram last time we repacked it but the last time I repacked it I had not been using the digging arm as much as i had been so there is a chance it could have bent a little. I will order a seal kit for it and see if that fixes it.
The oddest thing is the one direction only.

So here is a new wrinkle. Since about 10 AM yesterday it has been 40 degrees. Had been in single digits or below for previous 2 weeks. Anyways, I went out and fired up the machine and lo and behold no crazy hydraulic noises or anything of that nature. Everything works great in the boom and bucket hydraulics. Any ideas on the culprit now? Ice in the hydraulics? Ice in the Joints? Still really no clue but seems to be operating well now.

 

[OldMachinist]

So here is a new wrinkle. Since about 10 AM yesterday it has been 40 degrees. Had been in single digits or below for previous 2 weeks. Anyways, I went out and fired up the machine and lo and behold no crazy hydraulic noises or anything of that nature. Everything works great in the boom and bucket hydraulics. Any ideas on the culprit now? Ice in the hydraulics? Ice in the Joints? Still really no clue but seems to be operating well now.

Or the last of the trapped air finally worked its way out of the system.

 

[discountufoparts]

Or the last of the trapped air finally worked its way out of the system.

Could be! I have the weirdest issues with the thing.