Backhoe LW-7 backhoe foaming out the dipstick

[johneic]

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 49 degrees, tractor hydraulics work fine. Any thoughts appreciated. It was the same temperature outside yesterday, hoe dug fine, I did not 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.

 

[dex3361]

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 49 degrees, tractor hydraulics work fine. Any thoughts appreciated. It was the same temperature outside yesterday, hoe dug fine, I did not 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.

Hydraulic oil foaming can be caused by moisture or contaminates in the hydraulic oil. Moisture in the oil can freeze and plug up the hydraulic oil as well.

 

[Bob Rooks]

...running 32 weight (oil)...

John, running 32 weight oil in cold climates could be part of your problem. I suggest using AW ISO 32 hydraulic oil, which is approximately the equivalent of 10 weight oil.

This seems like déja vu... :laughing:

 

[traktorz]

I've got a similar setup like you, with a 7 GPM pump attached to a LW-7 BH, see the referenced big thread.

Your choice of hydraulic oil is fine. ISO VG 32 should be well suited for your working temperature, even so the ISO VG 46 which has the largest recommended temperature span should do.

It's a good practise warming up the oil and the system when digging below freezing. Since it's an open hydraulic system, at least you know that part of the system is working. If foaming, you should be hearing some growling sound from the pump, didn't you? I can see two reasons for foaming, either the oil reservoar level is too low causing pump cavitation, or some restriction occurs in the system or at the return line back to the reservoar.

Restrictions could be anything from an underdimensioned tank return hose, clogged tank return filter, a broken o-ring clogging a valve spool or a cylinder hose.

Checking the oil level is easy. If still problems, try to identify which branch from the valve unit is causing the foaming problem. Examine one cylinder function at times, observing the oil flow. Keep us updated on your progress! Like other LW-7 owners will, I'm interested in your findings.

Ref:

• LW-7 Backhoe at Chinese Tractor World Forums - chinesetractor.proboards.com

 

[RonMar]

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 49 degrees, tractor hydraulics work fine. Any thoughts appreciated. It was the same temperature outside yesterday, hoe dug fine, I did not 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.

Please clarify what oil you are running. I am guessing that you meant that it was AW-32, as I have never heard of 32 weight oil If it is AW-32 hydraulic oil, then it is as mentioned about 10 weight and what you should be using. If it is indeed 32 weight oil, I would get that out of there as that is too thick for cooler climates.

First thing I would check is the hoses and fittings/seals on the suction side of the pump. A pinhole of a leak here at a loose fitting would cause air to be sucked in ahead of the pump and cause your lack of power, foaming and jerky operation. Of course cold/thicker hydraulic oil will make this problem worse, and your description of it working better when it warmed up a bit leads me in this direction... It could also be a bad internal pump seal, but I would try and eliminate the easy stuff first. IMO, the ONLY places you can get foaming from is the pump or possibly at the reservoir. Everything after the pump is under positive pressure so no way for air to enter there. If the fluid at the reservoir returns at a high velocity into the airspace in the top of the reservoir, it can entrain air bubbles into the oil at the reservoir. Try filling a bucket of water with a high velocity straight stream of water to see what I am talking about. My HW-03 did this untill I replummed the fluid return port into the tank...

 

[Diamondpilot]

Sounds like air getting into the system.

Chris

 

[johneic]

Hydraulic oil foaming can be caused by moisture or contaminates in the hydraulic oil. Moisture in the oil can freeze and plug up the hydraulic oil as well.

Thanks Randall, I just did a complete oil change from 20 to AW32, I am ruling out moisture for right now as its always inside.

 

[johneic]

John, running 32 weight oil in cold climates could be part of your problem. I suggest using AW ISO 32 hydraulic oil, which is approximately the equivalent of 10 weight oil.

This seems like d駛a vu... :laughing:

So sorry all, I am no hydraulic man, but I am learning, it is AW32 which I assume is AW ISO 32, I bought it from NAPA.

Thanks Bob

 

[johneic]

I've got a similar setup like you, with a 7 GPM pump attached to a LW-7 BH, see the referenced big thread.

I read your thread on that site about two months ago as I got into this, nice write up, thanks

Your choice of hydraulic oil is fine. ISO VG 32 should be well suited for your working temperature, even so the ISO VG 46 which has the largest recommended temperature span should do.

Running AW32, which I think is AW ISO 32

It's a good practise warming up the oil and the system when digging below freezing. Since it's an open hydraulic system, at least you know that part of the system is working. If foaming, you should be hearing some growling sound from the pump, didn't you? I can see two reasons for foaming, either the oil reservoar level is too low causing pump cavitation, or some restriction occurs in the system or at the return line back to the reservoar.

Warmed it up (ran it at 1,000 RPM) for about 45 minutes

No growling from pump

resouvour is not too low, about an inch from the top of tank, less as this went on.

I am not ruling out the restriction on the return line yet...

Restrictions could be anything from an underdimensioned tank return hose, clogged tank return filter, a broken o-ring clogging a valve spool or a cylinder hose.

Checking the oil level is easy. If still problems, try to identify which branch from the valve unit is causing the foaming problem. Examine one cylinder function at times, observing the oil flow. Keep us updated on your progress! Like other LW-7 owners will, I'm interested in your findings.

I am not sure how I can do this, please explain, look in the tank with a mirror while running only one function?

Thanks again

Ref:

• LW-7 Backhoe at Chinese Tractor World Forums - chinesetractor.proboards.com

I have to write more to get this to post, I have a pressure gauge on the 3/4 hose I put on the pump, it sticks at 2,200lbs

I answered traktorz questions mixed in above, sorry if its hard to follow, I'll do this differently if needed, it works differently on another site I am on more.

 

[johneic]

Please clarify what oil you are running. I am guessing that you meant that it was AW-32, as I have never heard of 32 weight oil If it is AW-32 hydraulic oil, then it is as mentioned about 10 weight and what you should be using. If it is indeed 32 weight oil, I would get that out of there as that is too thick for cooler climates.

First thing I would check is the hoses and fittings/seals on the suction side of the pump. A pinhole of a leak here at a loose fitting would cause air to be sucked in ahead of the pump and cause your lack of power, foaming and jerky operation. Of course cold/thicker hydraulic oil will make this problem worse, and your description of it working better when it warmed up a bit leads me in this direction... It could also be a bad internal pump seal, but I would try and eliminate the easy stuff first. IMO, the ONLY places you can get foaming from is the pump or possibly at the reservoir. Everything after the pump is under positive pressure so no way for air to enter there. If the fluid at the reservoir returns at a high velocity into the airspace in the top of the reservoir, it can entrain air bubbles into the oil at the reservoir. Try filling a bucket of water with a high velocity straight stream of water to see what I am talking about. My HW-03 did this untill I replummed the fluid return port into the tank...

Hi Ron, it is AW-32 from NAPA, I removed the stock suction banjo fitting on the tank and had a welder enlarge it and weld in a 90 degree 1.25 inch elbow, put a 25 gpm filter inline with a vaccume gauge that reads zero when normal running and one at stone cold.
I could have allowed an air leak anywhere in this (I did try to make sure all my fittings were tight, filter gasket oiled and turned filter 1/2 turn after contact with gasket) (Funny this set up worked fine for the first day of digging than I had this problem on the second day, I wonder if I knocked something loose?)

I am leaning toward air intrusion on the suction line, at least that is where I will look first, all I know to do is check all my fittings, I bought 10 constant torque hose clamps to replace all the standard hose clamps I used.

Is there a way to test for leaks all along my (new) suction hose, fittings and all?, Like coat soapy water all along the suction hose and see where it gets "sucked" away? I assume the soap contamination would be small? or some other test?