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December 11, 2011
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johneich
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| Lifetime Member | posts 22 | |
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Post edited 1:11 pm – December 11, 2011 by johneich
Hi, this is for a LW7, running a prince 7 gpm pump, fed with 1.25 inch hose, 3/4 inch outlet hose. It was 24 degrees this morning, 34 now, 10:45am, no power when I first started to dig, I let it high idle for about 45 minutes with the pump on, ran it at 1,200 RPM, I then had decent power to dig but it started to foam up and come out the dipstick and fill neck, running 32 weight, Oil is 55 degrees, tractor hydraulics work fine, I have a septic tank coming tomorrow, I need to dig. Any thoughts appreciated. It was the same temperature outside yesterday, hoe dug fine, I didnot change anything overnight, tried to dig at idle speed, was jerky almost no power, ran it up to 1,000 RPM. decent power, started foaming out the dipstick again.
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December 11, 2011
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Bob Rooks
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| Lifetime Member Platinum Elite | posts 868 | |
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If you have a magnetic heater stick it on the bottom of the hydraulic reservoir. It sounds like you might be getting cavitation from cold oil on the suction side. I've seen that before but not at 34°.
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December 11, 2011
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johneich
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| Lifetime Member | posts 22 | |
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Post edited 5:01 pm – December 11, 2011 by johneich
Well its pretty nice out now, boom would not lift so I swapped the thumb valve hoses for the boom hoses and had the same problem. I assume this means my cylinder is bad. Any opinions welcome
PS when it foams out the dip stick I am trying to lift the boom with no success, I am essentially deadheading it (Not real long).
PSS 2,200 PSI on my gauge, filter vaccume gauge reads zero (Brand new cartridge, showed about one stone cold at 25 degrees)
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December 11, 2011
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Bob Rooks
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| Lifetime Member Platinum Elite | posts 868 | |
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Does everything else work ok except for the boom?
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December 11, 2011
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johneich
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| Lifetime Member | posts 22 | |
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I guess, new hoe first real dig with it. Bucket opens and closes good, dipper works fine, swing left and right is sloppy but I understand the swing cylinders are a weak point on this hoe. I never really had a chance to test the thumb, works fine, I needed the dipper and bucket hooked up to see if it would pick up a bucket of dirt, so disconnecting the thumb was my only choice. I might add, boom did come up with no dirt in it, just wold not come up with a full bucket of dirt.
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December 11, 2011
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Bob Rooks
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| Lifetime Member Platinum Elite | posts 868 | |
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Post edited 7:24 pm – December 11, 2011 by Bob Rooks
Two possible scenarios John:
1) Boom cylinder cup seals are bad, oil is by-passing. Possible early indication of eminent failure.
2) Debris stuck in relief valve, preventing full pressure.
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December 12, 2011
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RonJ
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| Lifetime Member | posts 35 | |
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Post edited 1:17 am – December 12, 2011 by RonJ
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December 12, 2011
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johneich
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| Lifetime Member | posts 22 | |
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I understand I can buy new seals, Ranch Hand Supply I think, how hard and what is the procedure to replace them? Special tools helpful? I only have O-ring picks.
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December 12, 2011
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Bob Rooks
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| Lifetime Member Platinum Elite | posts 868 | |
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Not sure if Ronald or Tommy carry kits for those cylinders anymore but you can check.
Circle-G does carry kits here.
Replacing the seals is pretty straight forward, the boom must be lowered and supported. If I remember correctly the cylinder doesn't have to be completely removed. just disconnect the rod end and remove the seal end of the cylinder and pull the rod and piston out. There are two types of cylinder seal ends used, one end screws on, the other uses snap rings. Be sure to relax all of the backhoe cylinders first, and have an oil catch pan under the boom.
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December 12, 2011
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johneich
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| Lifetime Member | posts 22 | |
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I just thought of one more test, remove the retract hose and open the extend valve and see if it bypasses oil.
My pressure is a constant 2,200 psi and I switched control valves from the thumb to boom to rule out a control valve issue, so the bypass oil test is the only thing left to test, I think, let me know, thanks all for the input.
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December 12, 2011
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Bob Rooks
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| Lifetime Member Platinum Elite | posts 868 | |
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I you fully extend the boom, dipper, and bucket off the ground, shut off the tractor and walk away, does the boom fall by itself?
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December 12, 2011
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johneich
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| Lifetime Member | posts 22 | |
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Bob, no, it stays up, no leak down at all.
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December 12, 2011
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Bob Rooks
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| Lifetime Member Platinum Elite | posts 868 | |
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OK, foaming in essence increases the volume of oil. Foaming is caused by turbulence, a natural occurrence in hydraulic systems. As a rule of thumb, the minimum reservoir capacity in gallons must equal or exceed the GPM rating of the pump. This allows for adequate time in residence to deairate the oil and allow for enough heat dissipation before continuing the cycle.
Are you using ISO AW 32 Hydraulic Oil specifically?
Is your reservoir at least 7-8 gallons?
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December 12, 2011
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johneich
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| Lifetime Member | posts 22 | |
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Yes, AW 32, from NAPA, reservoir is 7 gallons, I understand, its just like Lens and I did the same mod as him, only difference is I have a 90 degree 3/4 inch elbow at the pressure side of the pump, I have tried it at all RPM levels from idle to 1,200, low idle the dipper and bucket chatter a lot and have little power, higher RPMs boom still has no power, bucket and dipper power is just fine.
Here is Lens, I dont have pics of mine yet, mine is just like this except for the 90 degree elbow out of the pump
http://www.ctoa.net/forum/trac…..oe/page-2/
I am just stumped, if it does not leak down, boom cylinders are not bad, right? I ran it with two different control valves, what next to check?
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December 12, 2011
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johneich
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| Lifetime Member | posts 22 | |
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Post edited 8:14 pm – December 12, 2011 by johneich
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December 12, 2011
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Bob Rooks
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| Lifetime Member Platinum Elite | posts 868 | |
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Post edited 11:12 pm – December 12, 2011 by Bob Rooks
"Bob, no, it stays up, no leak down at all."
Let me clarify something. If the seals are leaking by the boom isn't necessarily going to come crashing down, instead look for small slow movement, say a few inches max. until the oil in the cylinder becomes "equalized" and a hydraulic lock occurs. At that point the piston will stop moving unless a valve is actuated. maybe try that again. I apologize for not being clear.
Also, try to positively rule out any suction side air leaks.
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December 13, 2011
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johneich
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| Lifetime Member | posts 22 | |
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Post edited 9:16 am – December 13, 2011 by johneich
"Also, try to positively rule out any suction side air leaks"
Recall I just replaced the factory suction hose with 1 1/4" hose and also put in an inline filter, I could have goofed up something there, I did my best to make sure my connections were tight,
How does one diagnose suction side air leaks?
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December 13, 2011
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Bob Rooks
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| Lifetime Member Platinum Elite | posts 868 | |
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Post edited 1:35 pm – December 13, 2011 by Bob Rooks
"How does one diagnose suction side air leaks?"
Not an easy question to answer, but I wouldn't use regular hose clamps with that type hose. I would use T-bolt clamps.
 
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December 14, 2011
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RonJ
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| Lifetime Member | posts 35 | |
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John,
If I wanted to see if I had a suction leak, I would wrap "saran" wrap around the suction hose and clamps – then see if there was any difference in the backhoe operation.
How do you have the thumb connected into the hydraulic system?
Since you are constantly getting 2200psi on the gauge, I don’t think that there is a Priority Relief Valve problem. Next thought would be a problem with the Boom spool.
I don’t think that swapping the thumb and boom hoses would give you the testing that you needed. I would have swapped the dipper and the boom so that boom spool could get a good strong exercise.
I gather from reading through the thread that you and LenBo did the same modifications on the LW07. I suggest that you might want to check with him to compare hydraulic tank information. Let me see if I can describe why I suggest this.
Over the years in talking to other Chinese backhoe owners, it became obvious that the same model number, year, serial number, etc. did not mean that the end product was the same.
The picture below is one that I put together for myself to better understand my backhoe. The external dimensions would indicate that it will hold about 8-1/2 gallons.. Over the years in talking with other owners, it took awhile to understand a major difference in tanks. With my tank on the left top there is an outlet designed for venting. This means that I could use 8-1-2 gallons if needed.
Others did not have this vent. I have drawn a red line at the bottom of the filler pipe that reduces the useable capacity to about 5 gallons. We determined that if their tanks were filled above the bottom of that pipe, there was a large buildup of pressure at the top of the tank. Some installed a vent pipe like mine and others came up with other venting solutions. This allowed them to put more useable gallons in the tank.
RonJ
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December 14, 2011
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johneich
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| Lifetime Member | posts 22 | |
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Ron, thanks for your comments
I like the saran wrap idea, will try it this weekend
Its a factory thumb, has a spool valve in the middle of the block, I will have to take pictures this weekend
I chose the thumb boom swap as I could reroute the thumb hoses to the boom. To test it I needed the dipper and bucket working so I could grab a bucket of dirt to test it. The boom hoses are not long enough to reroute to another cylinder. I do not have adapters to fashion an extension of the boom hoses. I am afraid to tinker the the hose fittings on the control valve block as I have read of them leaking after being disturbed.
I will compare my tank to your drawing this weekend.
I have checked with Len he most be real busy, no response.
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