John Deere 2040 Hydraulic squeal fixed or not?

[Jim83]

I removed the check valve between the transmission hydraulic pump and the front main pump, and the squeal from the front pump is gone after listening to it for 3 years.

Can I leave out the check valve? or will this cause other issues?

Any guesses as to why removing this check valve got rid of the lines shaking and the front pump squealing?

Any help would be appreciated.

Jim

Texas

 

[Jim83]

The check value is on the supply line going to the front pump

 

[Tx Jim]

Welcome to TBN
Is your tractors serial # below or above 266,749? My guess is with check valve missing that hyd squeal is missing then check valve must have been blocking flow to pump. My 1st thought is check valve/seat were installed backwards.

 

[Jim83]

Thanks for the response, I agree that the check valve must be reducing the flow of oil to the front pump somehow. I looked at the manual 6 times to be sure I had the check valve installed correctly.

I also looked at it from a logic standpoint of oil flow, and it seems logical. The ball is on transmission pump side, and the spring is on the front pump side. I assume the transmission pump pushed oil and opens up the check valve, I also assume when the tractor is not running, this check valve stops oil from running back into the sump area of the transmission pump from the front pump .

I just wonder if leaving the check valve out is going to cause a problem, and I also wonder if the transmission pump is getting so weak it will not push enough oil past the check valve for proper operation. I check the transmission pump last year, and it had good flow.

With the check valve out, the tractor sounds better that it has in 3 years. The front pump is not squealing anymore and the lines are not shaking. 319000L

 

[Jim83]

319000L

I did notice that in one john deere schematic the check valve was on the supply line that goes to the oil reservoir, and on another diagram the check valve is on the supply line that goes to the front hydraulic pump.

 

[Tx Jim]

Tech manual 4300 for 2040 shows check valve on line leading to hyd pump from hyd filter. Ball on check valve is on filter end. Your tractors serial # indicates it has closed center hyd system.

 

[Jim83]

Thanks you! That is the way I believe I had everything put together. My guess is the transmission pump is a little weak or other blockage causing this.

Anyone know why there a two supply lines to the front hydraulic pump? One goes to the top of the oil reservoir and the other one with the check valve goes directly to the front hydraulic pump?

 

[Zebrafive]

Thanks you! That is the way I believe I had everything put together. My guess is the transmission pump is a little weak or other blockage causing this.

Anyone know why there a two supply lines to the front hydraulic pump? One goes to the top of the oil reservoir and the other one with the check valve goes directly to the front hydraulic pump?

That's return/overflow from the reservoir. If you have an oil cooler (right of radiator), flow will first go through the oil cooler, then return to sump.

 

[Jim83]

Thank you !!- Ok, that make more since - I don't have an oil cooler, but I understand now. Any excess oil flows out of the top of the reservoir back to the sump.

I am beginning to think no one knows if the check valve on the supply line to the front hydraulic pump is important or not. I will likely just run the tractor without the check valve since it seems to run so much better without the check valve.

 

[Harry in Ky]

I'm by no means an expert on this system, but my feeling is that Mother Deere didn't put that check valve in there just so people could guess at it's purpose. I would suspect that without it, over a long enough period of time, much of the fluid in both the surge tank and even the pump could eventually drain back into the filter and transmission pump circuit leaving the pump relatively empty. On startup in this condition it could take a while for that fluid to made up so the hydraulics and steering will function. Would that happen overnight? Probably not, but after a few days/weeks of non use it might show up. I'm not saying there isn't a problem of some sort with your check valve, but it would seem to me repairing or replacing it might be a better alternative to tossing it under the bench.

 

[Jim83]

Thank you for your response. The check valve I put in was brand new. The old one had a broken spring, so I do not think it has been working properly ever since I bought the tractor three years ago. The new check valve made the hydraulics shutter even worse than it did before with the broken spring check valve. I got on this forum because I want to use the check valve if possible. But I also want the tractors hydraulics to work properly and not be under a strain all the time. A catch 22 as far as I can tell right now.

Thanks again for your advice, I agree. Leaking back was my major concern!

 

[Zebrafive]

When you have the optional HI/LO or Reverser transmission, JD does NOT install inlet check valve.
I am not sure how much oil could flow back through a gear pump. The transmission pump is a gear pump.

 

[Jim83]

Zebrafive - Thank you ! Very interesting comment. The transmission pump supplies oil to the gears and the front hydraulic pump. If the oil will not go through the transmission pump gears, I wonder if it can go out where it lubricates the actual transmission gears?

I also think I may be ok because the supply line is higher at one point than the hydraulic pump up front. Because of the high point in the line, even if it leaks back some, there still should be enough oil left in the hydraulic pump up front to be just fine. Any way, that is my thought to this point. I would put the check valve back in real quick, except for the fact that the tractor runs so much better without it. The tractor is so much quieter than it was, I could hardly believe it. I plan on monitoring all this real close for a few months. I also plan updating everyone with my results. Thanks to everyone for giving input! Jimmy in Texas

 

[DLTTrekkers]

I find with that squile that the main pump s pressure is to low and when you adjust it to the correct pressure the squile gose away.

 

[Jim83]

I'm by no means an expert on this system, but my feeling is that Mother Deere didn't put that check valve in there just so people could guess at it's purpose. I would suspect that without it, over a long enough period of time, much of the fluid in both the surge tank and even the pump could eventually drain back into the filter and transmission pump circuit leaving the pump relatively empty. On startup in this condition it could take a while for that fluid to made up so the hydraulics and steering will function. Would that happen overnight? Probably not, but after a few days/weeks of non use it might show up. I'm not saying there isn't a problem of some sort with your check valve, but it would seem to me repairing or replacing it might be a better alternative to tossing it under the bench.

Hey Harry in Ky, I found someone that thought that the check valve was in case of a surge back pressure. Any thoughts on back pressure? He thought I might blow some seals out if I left the check valve out. I am going to look at the schematic to see what seals he is talking about. Anyway, I thought you might find this interesting. Jimmy

 

[Harry in Ky]

I have no idea where this person got that, but who knows? As I stated earlier, I'm no expert on this system and won't claim to be. I can say I've learned enough to have solved all the problems I've run across so far. My understanding is the standby (or working) pressure is isolated from both charge pressure and whatever overflow/return pressure works it way through the cooler and back to the transmission, so where would a surge of back pressure come from? If he can explain that, I'm willing to entertain the concept. There are also a filter relief valve and a transmission pressure regulator that should reduce said surge effect before blowing any seals.

Personally, I have never seen a check valve such as you described on any of the tractors I've worked on. Maybe I just never noticed, or never had occasion to get into whatever component contains one. I'm not sure if you mentioned where in the system it's located.

 

[Tx Jim]

Jim83
I think presence or absence of this low pressure(155-165 psi) check valve will have little affect on whether a hyd seal fails. May I ask where this info originated?

 

[Tx Jim]

Personally, I have never seen a check valve such as you described on any of the tractors I've worked on. Maybe I just never noticed, or never had occasion to get into whatever component contains one. I'm not sure if you mentioned where in the system it's located.

Check valve is designed to be located in hyd oil supply line from trans pump to frt pump.

 

[Zebrafive]

Check valve is designed to be located in hyd oil supply line from trans pump to frt pump.

Correct, this the check valve we are talking about, and he removed. I posted earlier JD does not install this check valve when HI/LO or Reverser transmission is installed.

 

[Cycledude]

Very interesting