dexta hydraulics

[db880]

Hello, i am new to the world of fordson dextas. i have been asked tolook at one with a hydraulic issue. it was initally intermittant to lift the 3 point arms and to tip a trailer, gradually getting worse at that until it packed in compleately. after a look at the rather milky looking oil i decided to remove the pump and filter amd have a clean up inside whilst i was at it, the metal gauze filter was full of a creamy substance stuck around the inside of it. So then i rebulit with new o-rings and fresh oil. strted tractor but to no avail still nothing working. when i put a gauge i on the pump housing i am only getting 5bar whatever i do, even at full engine revs, with no change when the quadrant lever is moved. being unsure about the tractor i tested another one which had also 5bar at tickover but then a full engine rpm we had 10bar. when the quadrannt lever is moved we then have 40br until the desired postion is reached. Am i correct to think about replacing the pump on my tractor or have i missed something? Many thanks in advance for any help recived>

Lawrence

[blue32]

Hi Lawrence, From your answer I,d not see any posiblity to explain any... (just becouse hydraulik is,nt like "change a plug" or something) but as I always ment, wear and damages in this system will in many case,s become of such as; -dirt - frozen - water, and small particles of this is flowing through your hyd.system. Rather this is the fault, then some farmer,s possible has been insides for some adj...??? - It is a strong hydraulik on Dexta,s soo I recomend that you have to find all tread in the forum about this subjeckt and start to seek some similar prob,s. - but it is people insides this forum who has all the expertize for this.

mikkel

[Brian]

To check your pump pressure you need to "dead head" it. You cannot do this just by moving the control lever.

Put the gauge back on the pump, lower the control lever, then pull out the Auxiliary Control Knob with nothing on the coupling. Bring the control lever towards the top of the quadrant slowly until the pump loads, then take your reading. It should be around 2000 psi.

If it is not then you have pump or Pressure Relief Valve problems, if it is then your problems are in the top cover. I suspect, from what you describe it could be there.

[db880]

when i have tried to dead head the pump i.e. by sending the oil to the trailer tipping pipe and moving the quadrant to its end stop the pressure still does not increase, it sticks to a steady 5bar. so am i still correct in thinking that it could be the pump? As if the filter has been blocked and starving the pump of oil this would slowly destroy the pump would it not and hence the hydraulics working and then slowly getting worse? Thanks very much for the helo, much apprecated. Lawrence

[Brian]

It could still be in the top cover, a stuck flow control valve could give you the same problem, so could a stuck PR valve.

The pump will wear out but it does not usually give an intermittent fault and it normally fails slowly, getting worse over time, unless an "O" ring blows. The most usual cause of pump failure is dirt in the oil causing scoring in the housing and wear in the bearings. Even when they were a "working" tractor, we did not replace many pumps or have to repair them. But she has done many years I suppose.

If possible, try another Auxiliary Service Chest before stripping anything else. That would confirm that the flow control valve is OK/not OK.

[db880]

i will have to find myself a chest to try but have no idea where to find one, are they still available?

[Brian]

Send me a PM, you might be close to me. You only need to borrow one for 30 mins to do a check.