Interesting Story - Still a problem

[DocD]

I want to start my story by saying that I have had a great Dealer and John Deere warranty service, but still am having a dilemma.

My story starts with buying a new cab 3720 - 2 1/2 years ago. From the start, the loader seemed to have some cavitation when lifting (been addressed here a few times without resolve). I brought this up to the dealer and the first time to the shop - changed the oil to all season, the second time - changed the pump (was on the low side of normal for psi) and hoses, the third time had the district JD rep. look at the tractor. It definitely could be reproduced and no-one knew what was wrong or what to do. Now after 2 years and 210 hours on the tractor, it was still doing this and JD said that they would graciously replace the problem. So here I am today with a brand new 2011 3720 (not so sure I like the new loader control handle with the thumb diverter, but that if for another post) so I definitely cannot "complain" about the service.

But..... here is the problem, the new one is doing the exact same thing - only maybe a little worse. After all the work that JD has done on this for me, I hate to say anything to them, but this looks to be a factory tractor problem. I guess my question would be - is anyone else having this problem....is it a problem with the way that the dealer is setting up the tractors....is it correctable???? It really doesn't bother me that much as far as the operation of the loader or tractor, but I am concerned that if the pump is cavitating (introducing air somewhere), I would think that it MAY reduce the life of the pump. Again, the old tractor had pump and all lines replaced (or so I was told) and this did not solve the problem. It seems to happen when I go forward with the Hydro, then stop (it is not a "too much demand" problem as I am stopped and not moving when lifting the loader) and when I lift the loader - it will chadder (cavitate) as I run it for a cycle or two. After about 2-3 cycles the cavitation with stop and it will operate smoothly until I go forward or reverse again. It also happens in the 3 pt. hitch, so it is seemingly a pump problem. It happen both in the winter and summer, and seems almost to happen more once the tractor is warmed up (not seemingly a viscosity problem). I really don't notice it in the hydro performance or in the steering of the tractor - so is it really a pump problem?????

Again, I want to say that I have been extremely impressed with the dealer and JD itself, but am at a loss for what to do next and would be interested to hear some advice (always great) from this board.

Thanks,
DW

 

[RoyJackson]

Why do you think it's cavitating? What are you comparing the 3720 to even think there is a problem? It may be the "nature of the beast".

I suggest you express your concerns to the dealer and ask them if you can try a few other tractors on the lot....not for trading or anything like that...but to determine if the cavitation is typical, or you're seeing normal operation and just have to live with it.

Frankly, I think both Deere and the dealer treated you exceptionally well.

 

[nike]

My cousin recently looked at tractors, he wanted to buy one. We looked at MF and NH. Both had some good features we both liked. When we test drove the MF it had a bad cavitation noise that the dealer said was normal. I researched this a bit, and found that a plugged hydraulic filter could cause this. It does not have to be totally blocked to cause cavitation.
On new tractors the filter should be changed after 5 or 10 hours of operation. When the welding of the hydraulic tanks some dirt can be left inside that cleaning does not get out.
Hope this helps.

 

[TractorTidy]

Of all the years of being a JD dealer, I have never seen them replace a tractor. You are VERY fortunate.

I've had them replace engines but even that started getting scrutinized further. You are one lucky man. Take it and run!

 

[dconine]

I think it may be the nature of the machine. I have a 2006 John Deere 4120 with 500 hrs. and occasionaly it will hesitate when lifting but you wouldnt notice it easily because it happens very quick. I just did a hydraulic fluid & filter change with Hy-gard oil, and it still occurs. Correct me if I'm wrong, but maybe it just happens on some machines.

 

[pdp11]

I'm not directly familiar with the 3x20 hydraulics. But if it's like the 2520, and I suspect it might be, then some of what you've said makes sense.

On the 2520, the steering runs off of the pressure from the charge pump of the hydrostatic drive, while the SCV and rock shaft control are supplied directly by the engine mounted pump. So your problem seems to be in common with the engine mounted pump circuit. Since the control valves are all open center, there should be a constant flow of hydraulic fluid through the circuit that supplies the control valves. It seems odd that cavitation would occur.

There appear to be a number of pressure tests and adjustments that can be made to relief valves and regulators. Based on your description of the symptoms, I have to wonder if it's a relief valve or pressure regulator that causes the problem. It still seems odd that it would happen to you on two different tractors.

 

[boggen]

i would say, different types of oil are causing things to foam up inside the pump and hyd lines.

now, take my words with a good amount of salt. i ran over some posts i do believe here and on other websites. when i did my searching for my 555c loader / backhoe. with overheating transmission, and looking at old oil. and i distinctly remember a couple different folks state. mixing different types of hyd oils can cause the oil to foam. foam in your hydraulic oil can cause pumps to cavitate (sounds like rocks being grinnded up inside of the pump, some folks may not be able to hear it))

if we were talking about pond pumps or well pumps for water. and you noted it sounded like rocks being grinning up inside the hyd pump. i would say you have something clogging up the line between inlet side of the pump, some place. could be a filter, or something else. but perhaps it is 2 different types of oil that is causing things to create foam.

what does the oil look like after running the tractor for a couple hours? does it look like regular old hyd oil? does it look white? or milky? or a different color?

=============
as far as cavitation like vibration effect in hyd hoses or valve. on my 555c loader/backhoe, the right outrigger (passenger side) i know there is something inside that line. and every now and then. that piece will go through the valve and also through the out rigger hoses. and it will vibrate and chug, and even had initial slow response but after a couple moments after that particle or what ever clears out, everything is fine.

===============
on another note, are you only opening the valve just a little bit vs wide open on the valve handle? is there a difference?

what about with low and high rpm? with valve partially open to wide open?

after running tractor for a couple hours and working the FEL and 3pt hitch. does the oil look milky? or a different color vs when the hyd oil is cold and has been setting there over night?

when you say 2 to 3 cycles, do you mean fully extending and then fully retracting the FEL arms cylinders and FEL bucket cylinders? or just one or the other or both?

you noted, standing still and using FEL, and then you just noted forward or reverse of tractor. but you never said anything about while tractor is moving and operation of the FEL.

is there any chance the hyd pump might be variable speed / flow / pressure. and the chadder, is coming from check valves or like. and once enough pressure is built up, the check valves are quickly opening and closing again as pressure slowly builds up?

 

[DocD]

i would say, different types of oil are causing things to foam up inside the pump and hyd lines.

--There should only be one type of oil in the lines as it just came from the factory.--


now, take my words with a good amount of salt. i ran over some posts i do believe here and on other websites. when i did my searching for my 555c loader / backhoe. with overheating transmission, and looking at old oil. and i distinctly remember a couple different folks state. mixing different types of hyd oils can cause the oil to foam. foam in your hydraulic oil can cause pumps to cavitate (sounds like rocks being grinnded up inside of the pump, some folks may not be able to hear it))

if we were talking about pond pumps or well pumps for water. and you noted it sounded like rocks being grinning up inside the hyd pump. i would say you have something clogging up the line between inlet side of the pump, some place. could be a filter, or something else. but perhaps it is 2 different types of oil that is causing things to create foam.

what does the oil look like after running the tractor for a couple hours? does it look like regular old hyd oil? does it look white? or milky? or a different color?

--The tractor now has 7 hours on it and it is clear oil without foam or milky color.--

=============
as far as cavitation like vibration effect in hyd hoses or valve. on my 555c loader/backhoe, the right outrigger (passenger side) i know there is something inside that line. and every now and then. that piece will go through the valve and also through the out rigger hoses. and it will vibrate and chug, and even had initial slow response but after a couple moments after that particle or what ever clears out, everything is fine.

===============
on another note, are you only opening the valve just a little bit vs wide open on the valve handle? is there a difference?

--No difference.--


what about with low and high rpm? with valve partially open to wide open?

--Again, no difference.--

after running tractor for a couple hours and working the FEL and 3pt hitch. does the oil look milky? or a different color vs when the hyd oil is cold and has been setting there over night?

when you say 2 to 3 cycles, do you mean fully extending and then fully retracting the FEL arms cylinders and FEL bucket cylinders? or just one or the other or both?

--Both the arms and the bucket cylinders do it - fully extending and retracting.--



you noted, standing still and using FEL, and then you just noted forward or reverse of tractor. but you never said anything about while tractor is moving and operation of the FEL.

--It also happens when moving the loader up and down with the tractor moving. It seems to NEED to have had the hydro prior to it happening. If I cycle it a few times the chatter seems to resolve - only after moving the tractor forward or reverse can I get the chatter to return.--



is there any chance the hyd pump might be variable speed / flow / pressure. and the chadder, is coming from check valves or like. and once enough pressure is built up, the check valves are quickly opening and closing again as pressure slowly builds up?

Was out last night blowing snow and it happened the whole time - was out there at least 1 hour. See responses above.

 

[aczlan]

Any chance you could make a videorecording of it making this sound?


Aaron Z

 

[DocD]

Any chance you could make a videorecording of it making this sound?


Aaron Z

It really isn't a sound, but more of a visual thing. It moreso stutters when going up and when "powering" down. Nothing really to hear, mostly visual. I will try - may be hard to see without actually "experiencing" it in the cab.