cropmaster 25c duff hydralics

Posted by davidbrownpower on 2014-08-17 13:15:00 

I have a david brown 25c petrol paraffin and the hydraulic arms go up but not down, my suspicion is that the valves are rusted because the backend had 5 gallons of water in it with little oil. so does any one have any ideas of how to get to the valves or ideas about the problem.
Posted by: JamesF on 2014-08-17 13:39:00 
If memory serves me correctly the valves are top of the hydraulic pump which is bolted to the front of the gearbox and there are some long control rods inside from the levers. To get at the pump you need to remove the gearbox top cover, steering column etc. you will then see the pump. Dies the control lever feel to be doing anything? It could be the rod inside which had come disconnected.
Posted by: davidbrownpower on 2014-08-17 13:57:00 
right I will look into that thank you for your help, you don't happen to know if a 900 backend will fit it do you.
Posted by: stuartyd11 on 2014-08-17 17:10:00 
Had a similar problem with my crompaster, it had lift arms that were stuck in the up position and it turned out that the piston was seized because the back end had been full of water. If the valves are okay then i would take a look at the piston.
Posted by: JamesF on 2014-08-17 17:16:00 
I'm not sure about the 900 back end. There were early and late 900s, some early 900 rear end parts may interchange.
There are people on the forum who know more about the early stuff than i do , they'd be able to tell you more.
Posted by: db2d on 2014-08-17 18:10:00 
If the arms raise but will not lower, the piston and lift valve are free but the hold valve is not lifting off it's seat ( probably seized )
The 900 Non Livedrive rear should be compatible.
Posted by: davidbrownpower on 2014-08-17 21:49:00 
thank you all for your reply's, How do I get to the piston is it near the valves or a completely different place. I will be doing more research about the 900 backend. thank you
Posted by: stuartyd11 on 2014-08-18 11:27:00 
To get to the piston unfortunately you need to remove the heavy cross bar which the drop links attach to at the rear of the tractor and also remove the banjo bolt which supplys the oil at the front of the cylinder. There are two cast units which have 4 bolts at either end of the bar, if memory serves you just need to undo these and the banjo bolt at the front of the cylinder, take the cross bar off and the whole cylinder should slide out. The cylinder and piston are on the nearside of the tractor.

I would try running the engine at high revs and moving the control lever up and down first as this can sometimes cure a sticky valve if that is the case
Posted by: db2d on 2014-08-18 12:43:00 
If the steering box is removed the main control valve and mechanism can be observed. I would expect this valve to be seized from the symptoms you describe. The by-pass control valve must be working to allow the linkage to rise. The linkage must be lowering over time so that it can be raised when the system is operated. If the linkage lowers over time the piston is not seized.
Posted by: davidbrownpower on 2014-08-19 10:02:00 
my tractor is fitted with traction control it wouldn't be a problem with that would it.
Posted by: db2d on 2014-08-19 20:06:00 
No, it is not the TCU that is causing the problem.