Need help! With hydraulic valves on DB 880 selectamatic

[shambles]

shambles here,

I am a bit old in the tooth, this is my first go at using the computer
How ever I am trying to help a friend out with his DB 880 Selectamatic hydraulic problem
I have established that the pump is working, but it will only raise the links until the weight is applied.
looking through the back cover of the valve and control mechanism I found that there is no cam or control links for the height and depth control, also no cable to the center link sensing attachment. There is a constant flow of oil coming from behind the bypass & hold valves.

All we require from the system is to raise the slasher so I figure that should be possible.
however the system had been neglected and there was plenty of water in the oil like weak milk Coffey. it has been cleaned out and replaced with Agri SAE20/40.

Question: Should the bypass and hold valves spools come out of the block through the top
when the caps are removed. (as I cannot get any movement at all) I am certain that the problem is a stuck valve.
I sure would like some info on this

I found this site very Informative on many different equipments
Well done to those responsible.

Cheers to all
Shambles

[Kenham]

Hello Shambles, this may be of no help to you at all but, I know from past experience DB hydraulics are a bit of a minefield and can make you pull your hair out! Im sorry I can't tell you about the valves but on three tractors I had dealings with the copper pipes that join the various services had split just where you could not see them,I think one runs across the inside of the axle and others are under the oil. One of the problems with David Brown hydraulics is trying to work out what lever does what , and then a few years later and I have forgotten again. Keep on with the computer , Ken

[deltasierra]

They are very hard to troubleshoot, a valve or control rod/cable out of adjustment will create havoc. You might find a workshop manual on EBay which will help but the easy option is to find an old mechanic who remembers how to fix them.


Dave

[2414.ginger]

They are very hard to troubleshoot, a valve or control rod/cable out of adjustment will create havoc. You might find a workshop manual on EBay which will help but the easy option is to find an old mechanic who remembers how to fix them.


Dave

Hi Dave
Does it make any difference if you change the height/depth control?
Also if you have drained oil/water mix you could have an airlock!
I have a CD copy of a workshop manual which does have a troubleshoot section, I would gladly share this with you if you let me have your email address, I got it from ebay, only cost a couple of quid.
HTH you
Pete

PS sorry, replied to wrong post.

[shambles]

Thanks for the insight everybody Its much appreciated I will let you know how I go with it

its nice to be able to get help like this even with my limited computer skills.

Martin AKA shambles

[Holger]

Hi Dave
Does it make any difference if you change the height/depth control?
Also if you have drained oil/water mix you could have an airlock!
I have a CD copy of a workshop manual which does have a troubleshoot section, I would gladly share this with you if you let me have your email address, I got it from ebay, only cost a couple of quid.
HTH you
Pete

PS sorry, replied to wrong post.

Feel free to upload the file to our download-section!

[hair bear]

Just a silly thought, I'm sure the old 990 I used to use had a dump valve lever somewhere beside or behind the quadrant. Could it be as simple as the dump valve partially open?

[essexpete]

Does Scooby still post on here? IIRR he is a DB man.

[Stormin]

Here's a good link for a start:-
http://www.dbtc.co.uk/index.php?module=Content&func=view&pid=182

Search the CMN dowloads for the full hydraulics manuals, here:-

http://www.classicmachinery.net/forum/app.php/dl_ext/?view=detail&df_id=218

Another useful site but it seems to be down at the moment:-

http://www.dbtc.co.uk/index.php?name=Web_Links&req=visit&lid=18

Most common problem is dirt in the orifice washer under the dump valve. Next most common is the spool valve partially seized. After that it's the latching valve which is next suspect, not allowing the spools to move properly. The last fault generally mean the hydraulic block has to come out. I'm part way through doing mine but foiled by a seized bolt on the lift arms.

[shambles]

Hi all
I worked on the tractor on the weekend using the manual that Pete sent me I was able to fix it.
Turns out the problem was almost exactly like Stormin described.
Both the bypass plunger and the hold valve were seized and the latching valve had so much gunk in it, probably unable to move as well, The ball retainer and ball were missing from the hold valve plunger. I ended up getting a ball from the idle pulley bearing of a broken down Murray mower.
I removed all the parts from the valve block laying them out on a piece of cardboard with the part number corresponding the exploded valve drawing, Cleaned and polished all the parts with metal polish, put it all back together again and it worked perfectly first time.

Thanks to all that posted to help me out I certainly would not have been able to do it without your help
Lots more work to be done to the old girl yet, so I will keep an eye on this forum

Special thanks to Pete for the manual

Much relieved
Martin AKA Shambles