John deere 4030 hydraulic problem

[Parr4030]

Hi. I purchased a 74 John deere 4030 in the fall and I have been working on it over the winter. I changed all fluids and filters. Everything worked fine. I hooked it up to my discbine this morning to service it and when I tried to swing out the discbine, I had no hydraulics and little to no 3 point arm lift. The power steering and quad range work fine. There are no leaks and no noises in the system. What should I be looking at? Any help would be greatly appreciated!

 

[ET]

Pull the suction screen and clean the brake pads out of it. Then a brake job will be next.

 

[Parr4030]

I forgot to ad that i pulled the screen when I was servicing it and it was clean.

 

[WTW]

Knowing the steering works fine,is indicating main hydraulic pump is working. Problem is the steering will function pretty much normal at a lower pressure. The remaining hydraulic functions are being shut by the priority valve limit that protects steering and brakes, The problem is pump pressure is too low to allow oil flow past priority valve to secondary functions, that are not working. Pump pressure needs to be adjusted up. In event it will not adjust up, main hydraulic pump needs a new stroke control valve which can be replaced/serviced in tractor. Very common simple fix. Good Luck, DW

 

[Parr4030]

That sounds like goods news for me concidering. I hope that's all it is. I'll look into that. Thanks!

 

[grwrench]

hello, you need to destroke your pump and see if things return to normal. pull down the LH. side screen, look in on top of the pump to see if you have a DESTROKE SCREW in place, [a threaded stud sticking up about 1 inch with a small roll pin crossway, making a tee so you can turn it by hand with the tractor running. turn it clockwise until it gets tight then one more twist to open the stroke valve, then back it out to home position, try this a couple times if it don't work the first time. IF you don't have the destroke screw you can get one from your dealer. of course you need to check system pressure to see if you have 2250 psi.

 

[Parr4030]

Will do and thanks! Why would I have good hydraulics one day and the next I have none? Literally, yesterday the 3 point was crisp and today, little to nothing. I just took it for a ride yesterday to run it a little after putting new rims on.

 

[Tx Jim]

I replied to your question on TractorTalk but I've thought of something else that hasn't been mentioned. Acquire a 5000# gauge and check stand-by pressure. As previously stated pressure should be 2250 psi. If stand-by pressure is above 1800 & 3 pt/scv's still don't operated correctly the pressure control valve(parts keys 2-7) could be stuck closed.

 

[Cliff Nelson]

If a piece of debris gets caught in the stroke control valve, the pump will not build pressure as the valve will not close completely. I have seen several do that over the years, some with other failures that contaminated the system and some with clean filter and screen with no other problems. It doesn't take much to hold the valve open so it doesn't work properly. And yes, it happens just like you said, working one minute and nothing the next.

 

[chuck from neb]

I would check the driveshaft connection between the front pump and the engine first ...sounds like the splines are stripped out...it's an easy diagnosis and very typical when hydraulics are working one day and not the next.

 

[JD Seller]

Chuck he has good steering so it is not the pump coupler. It more than likely is low pressure causing the priority valve to shut the rear hydraulics off.

 

[johnyquest69]

I have been going through some of the same problems. Changed stroke control valve and nothing. I broke line loose at block 29 in picture Jim posted at coupler 27. Nothing at first and then oil shot everywhere. My scv's and lift then started working. I still think something is wrong and tried to check clutch pressure at port under battery box with 300# gauge. It showed nothing, but everything seems to be working at the moment. Duh????

 

[buickanddeere]

(quoted from post at 14:01:38 03/07/16) I have been going through some of the same problems. Changed stroke control valve and nothing. I broke line loose at block 29 in picture Jim posted at coupler 27. Nothing at first and then oil shot everywhere. My scv's and lift then started working. I still think something is wrong and tried to check clutch pressure at port under battery box with 300# gauge. It showed nothing, but everything seems to be working at the moment. Duh????

Pull the innards from the priority valve and monitor the high pressure side of the system.
Are one or both pumps not keeping up due to pumping problems? Or is there a low pressure or high pressure internal leak.

 

[johnyquest69]

Can you describe pulling the innards? I'm also wanting to verify this is the priority valve. Can I check at test port on priority valve? Any advice appreciated! I checked heat temperature on some of the components and most everything was around 130 degrees. The priority valve was about 150. Wishing it could be this!!!

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