Db990 Lift arms wont suddently move

[JacobJ]

Hello all

New troubles with my db 990..

I was moving some 500 kg containers today and it went all well untill I was on a slight decline and had to lower the lift and realigne the container that had slipped a bit. When I wanted to lift the lift again it didnt move. Nothing worked..

If I put the control lever all the way back I wont hear the pressure releif valve open, as it did untill then.

I have taken the front cover off the quadrant housing to see if the there is something wrong with the control push rod. I can't see that.

I tried pulling out the hydraulic dip stick and the fluid is whitish with bubbles.. That doesn't look right??

Hope you guys may have some ideas.

/ Jacob

 

[Alchad]

They might do but would like to know what’s happening about the overheating problem first!

But being charitable - sounds like You’ve got water in there, drain and replace with fresh is the first solution, and replace any filters ( dont know the 990, so join the `FB David Brown Tractor, Operator and Enthusiasts Group - they have manuals etc for most D`B’s in the files section)

 

[Mur Huwcun]

Implematic or Selectamatic? If you have any water in a DB hydraulic system all manner of valves start to stick and play up. My money first would be the dump valve sticking and dumping all the flow back to back end. Remove dump valve lever and look into the hole and you will see the valve. A wooden dowel stuck into it will fish it out if it won’t come with a magnet. You can clean it all up and lubricate and re fit and it may well behave!!

 

[Netherfield]

Usual place for water to get in is through the gear levers, lack of gaiters normally.

Implematic or Selectamatic? If you have any water in a DB hydraulic system all manner of valves start to stick and play up. My money first would be the dump valve sticking and dumping all the flow back to back end. Remove dump valve lever and look into the hole and you will see the valve. A wooden dowel stuck into it will fish it out if it won’t come with a magnet. You can clean it all up and lubricate and re fit and it may well behave!!

Give the area a good clean before you do though, muck in the control valve is a killer.

 

[Bald n Grumpy]

Implematic or Selectamatic? If you have any water in a DB hydraulic system all manner of valves start to stick and play up. My money first would be the dump valve sticking and dumping all the flow back to back end. Remove dump valve lever and look into the hole and you will see the valve. A wooden dowel stuck into it will fish it out if it won’t come with a magnet. You can clean it all up and lubricate and re fit and it may well behave!!

Your right , I'd almost 90% say it's the dump valve. The valve that needs cleaning will be under the screw in plug next to the hole you mentioned. Remove valve then unscrew brass plug tap out small disc with pin hole in and clean and reassemble..
Sounds like it needs a filter and oil change also,would recommend new gear stick gaiters as that's a good point for water and dirt to get in , get a lot less hydraulic trouble with Q cabs on compared to no cab

 

[JacobJ]

They might do but would like to know what’s happening about the overheating problem first!

But being charitable - sounds like You’ve got water in there, drain and replace with fresh is the first solution, and replace any filters ( dont know the 990, so join the `FB David Brown Tractor, Operator and Enthusiasts Group - they have manuals etc for most D`B’s in the files section)

Yes, the temperature problem is still an issue, but this is much more a problem for me. The tractor is now completely useless for me.. But I will get back to that the minut I have fixed the other problem.

Yes it seems like I need to do that anyways, but didnt think it would cause the lift not to work from one moment to another.

Thanks for the suggestion to join a group. Is that on Facebook?

 

[JacobJ]

Implematic or Selectamatic? If you have any water in a DB hydraulic system all manner of valves start to stick and play up. My money first would be the dump valve sticking and dumping all the flow back to back end. Remove dump valve lever and look into the hole and you will see the valve. A wooden dowel stuck into it will fish it out if it won’t come with a magnet. You can clean it all up and lubricate and re fit and it may well behave!!

Selectamatic. As said, I sure think I need to put new oil and filter on it.

The dump valve was in my thoughts, but again, would that show from one moment to another? Hmm and would that also result in that the pressure relief valve would not kick in, when I push the control lever all the way back in the select mode?

 

[Netherfield]

Simple, but you haven't just knocked the selector lever at the left of the seat over.

 

[Bald n Grumpy]

Selectamatic. As said, I sure think I need to put new oil and filter on it.

The dump valve was in my thoughts, but again, would that show from one moment to another? Hmm and would that also result in that the pressure relief valve would not kick in, when I push the control lever all the way back in the select mode?

If the pin hole in the disc in the dump valve gets blocked it can happen in a split second and your hydraulics are dead , have you been back and tried it since?
It may clear for a short time if your lucky

 

[Mur Huwcun]

Selectamatic. As said, I sure think I need to put new oil and filter on it.

The dump valve was in my thoughts, but again, would that show from one moment to another? Hmm and would that also result in that the pressure relief valve would not kick in, when I push the control lever all the way back in the select mode?

Our one used to do it everytime you wanted it working!! Couple back end flushes with 5gallon of diesel a go and then a fill with used SUTO oil from a younger tractor after a 1200hr service and she behaved then intill you left it standing too much!!

 

[JacobJ]

Simple, but you haven't just knocked the selector lever at the left of the seat over.

No it is in the lift selection, so sadly that isnt the case..

 

[JacobJ]

If the pin hole in the disc in the dump valve gets blocked it can happen in a split second and your hydraulics are dead , have you been back and tried it since?
It may clear for a short time if your lucky

Yes I had it started today and its all the same.

 

[Bald n Grumpy]

Yes I had it started today and its all the same.

Need to clean the dump valve, if that works then an oil change and filter will be very beneficial

 

[Skintagain]

Need to buy a mf 135…..

 

[Exfarmer]

In the dump valve is a little ball, lose that at your peril!

 

[Bald n Grumpy]

In the dump valve is a little ball, lose that at your peril!

Won't make any difference, most of them are long gone

 

[JacobJ]

Okay. Yesterday I finally had the time to try to fix the tractor. I took the dump valve off, the spring, the plate with three holes and a small steel ball out and also the valve itself (the trick with the wooden dovle work very well). It all looked fine, but I cleaned it and put it together again. But, it is still not working.

I tried to put a wagon I got on hand onto the rear output and used the selector valve to try to see if the wagon would rise, hence the hydraulic pump is working, but it didnt rise. But then again I dont know if that also is feed through the valve chest somehow?

But, hmm. Could it be a problem with the bypass valve (the one next to the hold valve the dump valve is placed apon)?

Hmm something else come to mind. What about the lowering speed valve, if that was come to far out? Could that be the problem? I remember turning on that, but if I did that in exactly the moment it went bad I cant remember.

 

[Bald n Grumpy]

Okay. Yesterday I finally had the time to try to fix the tractor. I took the dump valve off, the spring, the plate with three holes and a small steel ball out and also the valve itself (the trick with the wooden dovle work very well). It all looked fine, but I cleaned it and put it together again. But, it is still not working.

I tried to put a wagon I got on hand onto the rear output and used the selector valve to try to see if the wagon would rise, hence the hydraulic pump is working, but it didnt rise. But then again I dont know if that also is feed through the valve chest somehow?

But, hmm. Could it be a problem with the pressure release valve (the one next to the hold valve the dump valve is placed apon)?

You've not cleaned the right valve, read my post number 5
It's the one under the screw plug next to it

 

[JacobJ]

You've not cleaned the right valve, read my post number 5
It's the one under the screw plug next to it

Doh... Nice its raining today, so I will try that. I'll get back, as soon I have tried that.

 

[JacobJ]

Hmm the cap on top is stuck. Tried grinding down an old chisel to make it fit the slot on top and took an adjustable spanner to turn it, but it is totally stuck.

I can see, that someone before my ownership has had some go at it too, so before I do anymore damage to the slot, I would hear you guys, if you got any tips?