3 point linkage operation issues

[DeanB]

Does anyone have any ideas what I'm doing wrong but I cant make the selectamatic system work, I've got a david brown 995 1976 with a three way valve operated from under the seat position with the selection 1 2 L and L1 as I under stand I needed to put this in L to work the rear linkage but all this does is release fluid out of a quick release hydraulic valve located to the upper left of the attached picture should this have a cap on it or am I doing something wrong. Any help would be appreciated

 

[Exfarmer]

The DB selectamatic system has 3 operator contoling levers.
the 3 way valve is one.
the main lever is the the quadrant lever where you raise and lower the implement either by way of draft, positions or TCU ( variable weight dispostion called Traction Control Unit.
to operate the 3 point linkage first L or L1 must be selected on the 3 way valve.
then decide how you want the linkage to work.
if draft, pull the quadrant lever dully to the rear and engage the small lever at the Right rear of the seat in the relevant sector, draft,position, TCU.
However the DB hydraulics were notorious for issues relating to contamination. The system was very advanced for its day, but were let down by the fact that dirt was always going to ingress through the trailer pipe outlet / return
the DBTC website forum is an excelent source of help

 

[DeanB]

When I select L or L1 fluid spills out of the valve in the picture should this have a cap or is it broken

 

[Boohoo]

So the lever in the cab is at L but you've got oil coming out of the tipping pipe?
Is the lever difficult to move? It should move easily and click between positions. I've seen levers and linkages partially seized, which then get bent, so you think the valve is in L but it's actually in 2.

 

[DeanB]

The lever is hard to move but I can hear the clicks as I'm moving through the selections

 

[Exfarmer]

Oil should not come out of the coupling when nothing is connected! It needs replacing.
however there are obviously other issues too.

 

[DeanB]

Looks like I need to give the system a full check up. Is there a specific name for the quick release coupling so i can replace that before getting my hands really dirty

 

[Boohoo]

Replace the fitting on the tipping pipe first. I'd replace it with a quick release fitting rather than another screw on fitting.
After that, trace the tipping pipe forward to the 3 way valve and see which port it is connected to. I'd also remove the linkage to the in cab lever and try selecting the various positions directly on the valve before starting to pull oily bits apart.

 

[DeanB]

I'll replace the tipping pipe valve with a new quick release because I've just searched Ebay and there isn't many about, are they a standard size quick release because this is my first tractor and this is all a learning curve for me. Hoping to totally restore the old thing in my spare time starting with stripping, welding and filling the cab before a new paint job.

 

[Boohoo]

I'll replace the tipping pipe valve with a new quick release because I've just searched Ebay and there isn't many about, are they a standard size quick release because this is my first tractor and this is all a learning curve for me. Hoping to totally restore the old thing in my spare time starting with stripping, welding and filling the cab before a new paint job.

This is the current standard for hydraulic quick release fittings

Pardon our interruption...

Screw on went out of fashion in the 80s. Not sure what else you'll need, best bet is to take the fitting off and take it to a local machinery dealer or agricultural merchant. They should have what you need.

 

[DeanB]

That's my job next weekend sorted thanks for the info

 

[Exfarmer]

Do not attempt to take the hydraulic valves apart, they need specialist knowledge i am afraid.
I would be wary even of any local workshop attempting it unless they have had prior experience.
generally they will get nowhere and have a large bill.
it is possible that there are issues with the dump valve which is quite simple and cheap, but there are small balls and springs in there which are so easy to lose and they are matched parts!

 

[Boohoo]

Do not attempt to take the hydraulic valves apart, they need specialist knowledge i am afraid.
I would be wary even of any local workshop attempting it unless they have had prior experience.
generally they will get nowhere and have a large bill.
it is possible that there are issues with the dump valve which is quite simple and cheap, but there are small balls and springs in there which are so easy to lose and they are matched parts!

Issues with the dump valve usually result in no flow, not flow to the wrong place. I'll put my money on either the 3 way valve or the linkage that works it.