Limp hydraulics

alang · Post by **alang** » Thu Mar 26, 2015 12:31 am

This is my plea for help after a few years away.
I need to put my ’58 Dexta back into work this spring. The hydraulics arms have been held in a half raised position with a drawbar and stays for a couple of years. After removing the drawbar and stays the hydraulics arms hung down and refused to lift when the quadrant is raised.
I took the top off, cleaned the linkage, replaced the o-rings, cylinder seal, new oil and return filter but still no movement with the qualitrol lever in either position. The auxillary supply valve slides in and out OK.
Any suggestions as to what to check next would be appreciated.

Cheers
Alan

Post by **Brian** » Thu Mar 26, 2015 10:24 am

Sounds like you have a hydraulic pump fault, have you got oil coming up into the hydraulic top cover? You could also have a stuck flow control valve in the Axillary Service Chest.

First take the ASC off and, with the stop pulled, operate the starter and see if you are getting oil out of the pressure feed. If oil is coming out of the pressure port, try and put your thumb over it and see if it builds up pressure. Do this by operating the starter, do not start the engine or it will get messy.

If you have got pressure, can you get another ASC to try. This will identify whether your problems are in the pressure lines.

alang · Post by **alang** » Thu Mar 26, 2015 1:08 pm

Thanks Brian,

I will take the axillary cover off and look for a pumped supply - having just forked out £70 for new oil you may rest assured the STOP will be out. If there is no supply I'll get the pump out - I didn't do that when the top was off before because I figured it was the lack of use that had caused the fault.

Does the pump bang away all the time on a 'Live' Dexta, even with the PTO out of gear?

Cheers
Alan

alang · Post by **alang** » Thu Mar 26, 2015 4:19 pm

I've got good pressure in the ASC, but don't have access to a spare unfortunately.
I re-fitted the ASC and tried the same test with the knob out and the auxiliary hose off - no oil came out

Any further check advice will be welcomed.

I saw a qualitrol video on YouTube <https://www.youtube.com/watch?v=kFGQZM57O64> that shows hand pressure on the top link lifting the arms. There is no way hand pressure will move my top link.

Post by **Brian** » Thu Mar 26, 2015 5:21 pm

Looks like your flow control is stuck, you may need to take the plug out and free it off.

You may find that when you have done that you will have to take the top off again if you did not check the control valve and the unload valve when you had it apart.

alang · Post by **alang** » Thu Mar 26, 2015 6:24 pm

Brian,

Perhaps I've confused matters, this link (system won't let me upload pictures directly) is a photo of my Auxillary supply, which does not have a control valve.
So do you suggest I look at the control valve and the unload valve within the top cover?

Cheers
Alan

I've edited the photo out because which ever Photobucket link I use gives full access to all my photo's - hope you can recognise the Auxillary supply from my description

Post by **Brian** » Fri Mar 27, 2015 8:17 am

No link?

alang · Post by **alang** » Fri Mar 27, 2015 8:56 am

Like I say Brian, the link exposed my whole library so I edited it out - I've put the picture in a separate album with a link below - hope it works.
[img]http://i629.photobucket.com/albums/uu17 ... aecdem.jpg[/img]

Post by **Brian** » Fri Mar 27, 2015 4:28 pm

That is the old ASC and does not have a flow control in it. Possibly the selector is not moving enough to let oil out. The oil flow is from the pump, up through the top cover, through that housing which diverts the oil to either the ram cylinder or external service.

The next place to look will indeed be back under the top cover and both the control and the unload valve I am afraid.

To get your picture to appear, there is a series of boxes to the right, if you click on the one marked IMG it will momentarily change to yellow and say "copied", you can then paste it into your post.

alang · Post by **alang** » Fri Mar 27, 2015 6:35 pm

Many thanks Brian,
I'll report back on the outcome.
I am used to posting pictures on forum sites - all that is happening is the script is copied not the image, as per my last post.
I see the forum can block a members ability to post pictures, perhaps I'm switched off

Post by **Brian** » Sat Mar 28, 2015 11:40 am

No, you are not banned from posting pictures as far as I know but I will check. The immage code in your post is the same as the one of the picture in my post so it should have worked.

Post by **Brian** » Sat Mar 28, 2015 11:47 am

Just testing with your permissions.

alang · Post by **alang** » Sat Mar 28, 2015 4:06 pm

Brian,

my fault the BBCode box was disabled...

Took the top off this morning. The Control valve slides in and out without a problem - adjustments are as per the book. Cleaned the Unload valve again. The piston is a little tight with the new seal (correct way round) but moves out with the aid of an air line. Put it back together without any success

Time to get a professional in - anyone know a good Dexta engineer around the Northampton, Leicester area?

Many thanks for the help,
Alan

Post by **Brian** » Sun Mar 29, 2015 2:42 pm

Any chance of borrowing another ASC? If you are getting oil up to the top but it is not getting to the ram cylinder/control valve the problem must be in there however unlikely. I had the same trouble with a local Dexta which had been checked and found OK. When I loaned him one of my spare ASC's his problems disappeared.

Did you use a Case New Holland "O" ring on the unload valve? If you used an ordinary one, that could give you problems. The CNH ones are made of a special rubber that does not deform when heated by the oil, should have a blue spot on it.

alang · Post by **alang** » Sun Mar 29, 2015 4:28 pm

Brian, unfortunately I haven't got access to a spare ASC.

I need to find a quick answer as the grass is starting to sprout. My old Hayter rotary mower has finally given-up and I'd rather be using the new flail mower on the Dexta (live clutch) than the TEF-20 (no over-run clutch), so I have booked a "Dexta" mechanic for Wednesday. He is convinced it's the unloading valve, from my description. We'll see.

Thank's for the O-Ring tip and all the other great help, which has helped reduce the time I need to pay for next week.

I will put the topic to bed with the final outcome asap.

Cheers
Alan

alang · Post by **alang** » Wed Apr 01, 2015 9:26 am

Brian,

My "expert" came out and declared he'd done plenty of stuck unload valves. I'd taken the top off and had it ready on the bench - he opened up his box of odd bolts, tried a few, found the "nearest" and promptly stripped out the first two threads. As he went for his "hammer" I decided we should part company.
Having seen your photo from bigmakatak's topic I've decided to carry on myself.

Found a bolt, extracted the plug - freed off the valve, brasso'd it, went to the local New Holland agent and got the blue spot O-ring, re-assembed and

Can't thank you enough - a donation has been made to The Fred Dibnah Memorial Fund - my way of saying thank you... hope you approve.
Cheers
Alan

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