JD 4630 hydraulic problem

[mechanicegf]

Having an issue with my 4630. When using it to the point of getting hydraulic oil hot, I lose pressure. I've changed the filter and cleaned the screen. I destroked the pump and got pressure back. Worked it for about an hour and lost it again. Destroked it again, worked for about 30 minutes. Shut it off for about 10 minutes, restarted it and had pressure back. Whenever I start it now I have pressure, but haven't used it to the point of getting it hot. Does anyone have any idea of what might be the problem? Should I just replace the pump, or the stroke valve, or something else? Any help is appreciated

 

[Tx Jim]

Sounds typical for hyd system having an internal high pressure leak. I suggest that when hyd's stop operating to check each hyd control valve with a laser thermometer. Hottest control valve is probably the source of loss of hyd pressure due to frt hyd pump cavitation due to lack of sufficient oil supply.

 

[used red MN]

Jim, if I may ask. You are suggesting the oil is too hot
and the viscosity is too thin to be drawn in by the trans
pump so oil is not available for the front pump and it
cavitates? Or the leak is just so large that the system
cannot keep up?

 

[buickanddeere]

The good news is that TimS has the experience and the calibration equipment to make the SCV better than new .

 

[tim s]

What transmission do you have ?

 

[Tx Jim]

used red MN
Most likely internal hyd leak is utilizing more oil than trans pump can supply BUT heat tends to thin hyd oil causing internal leak to normally be larger. Only real method to determine hyd problem is by completing good hyd diagnostic procedures everything else is just a "guess"

 

[WTW]

If the system returns back to working when you de-stroke pump out and back in when oil is hot, I
would recommend to replace the stroke control valve in pump first. It may be sticking and it also
may have its seat surfaces worn and stroke control valve is just leaking too much when oil is hot.
They do wear out and do this. Are you using hydraulic system to run something causing normal heat or
is system getting hot just setting and running? May need to diagnose what is leaking generating heat
if heat is above normal. How hot is it? Hydraulic temperature can get as hot as engine coolant temp
if you are working system to its capacity on hot days?? When condition occurs and it happens for
fast for no reason (no slowing down of flow first) The pump stoke control valve is caught open.

 

[mechanicegf]

(quoted from post at 03:59:45 08/14/23) What transmission do you have ?

Quad range? It's the A B C D 1 2 3 4 one.

 

[mechanicegf]

I'm not sure of hydraulic temp. I don't believe it's too hot. But I was using it to bale hay the end of July. Outside temp was in the 90s.

 

[used red MN]

Jim, Thanks for the clarification!

 

[mechanicegf]

I appreciate everyone's response. Thank you very much

 

[buickanddeere]

I was positive that I had the tractor s Rad
And oil cooler were completely cleaned .
Had the sheet metal off for another job and took a look through the Rad cores and was embarrassed . The rads were still half plugged . A further session with compressed air and the hot water hose at 50psi lifted an amazing amount of oily dirt
From the fins .