990 selectamatic ,hydraulics help!! Please.

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bigjay
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990 selectamatic ,hydraulics help!! Please.

Post by bigjay » Fri Apr 22, 2016 6:32 pm

Hi all , just signed up to this forum . Ive purchased adavid brown 990 selectamic and struggling with the hydraulics . When i first got it i was aware the front loader didnt work .
I have changed the oil and filter underneath . Taken the dump valve off and what im sure is the 'by-pass valve next to that ??? I cleaned both valves there, one with the ball bearing and 3hole mesh thing . And the other hole with the brass screw down the bottom and there was an aluminuim washer with the tiniest hole init know to man!! With the mesh underneath that.... Anyway , managed to clean all of that and when put all back togeather the loader worked!! Im not sure on the back arms as unsure how to operate them . But i loaded the front loader with 90 kg and it struggled to lift ut. So up the revs alittle and it was lifting it but very slow ??? So im thinking restricted oil feed? Or possible pump? I am a mechanic so have good knowledge of things but hydraulics?? Sorry totally out of ideas.
Any help would be greatly appreciated as u have a log splitter turning up at end of next week and wanted the hydraulics to run that . Saves my little hamds on an axe all day. thanks guys .

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bigjay
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RE: 990 selectamatic ,hydraulics help!! Please.

Post by bigjay » Fri Apr 22, 2016 7:42 pm

Sorry with all the questions guys !! ...... With the two valves ontop , was there suppose to be two sleevethings that come out? (One from each one?) one under the dump valve was free and came out but the sleeve with the tiny hole washer and mesh didnt come out if theres suppose to be one there? I had to fish the mesh and washer out with some really funky home made contraptions!! Haha. Thanks guys :D :D :D

Scooby
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Post by Scooby » Fri Apr 22, 2016 8:30 pm

Firstly congratulations on buying one of the best and most popular DB tractors ever made and welcome to the DBTC Forum. May I suggest that you avail yourself with an operators manual. The Selectamatic hydraulics were, without a shadow of doubt, the best hydraulic system that was available on any British tractor at the time. When they are on-song and adjusted correctly there was nothing to touch them but you do need to know how to use the system. The manual can be obtained from the on-line shop. http://www.dbtc.co.uk/shop/index.php?ro ... uct_id=118

Secondly, we have been very fortunate in having a couple of gentlemen spend some time putting together a schematic explanation of how the system works. Have a look at THE SELECTAMATIC HYDRAULIC SYSTEM option in the Main Menu on the left. Please give it time to load properly.
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Three is twee, four does snore, but 6 just clicks........Scooby

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bigjay
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Post by bigjay » Fri Apr 22, 2016 8:34 pm

Thanks for your reply much appreciated.

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bigjay
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Post by bigjay » Fri Apr 22, 2016 9:38 pm

Just been out to the old girl again and have notice the by-pass valve plunger is well and truly stuck . Any way of getting these out ????? Thanks

Scooby
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Post by Scooby » Sat Apr 23, 2016 6:20 am

bigjay wrote:Just been out to the old girl again and have notice the by-pass valve plunger is well and truly stuck . Any way of getting these out ????? Thanks
Now this where it starts to get a bit technical. Go to your nearest hedgerow and cut a piece off a nut bush that is slightly larger than the valve body. Take the bark off the piece of nut and push it into the valve. With a bit of luck you will be able to wriggle it out.

I was taught to do this by a DB trained workshop foreman 50 years ago so it must be O.K. :D
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Three is twee, four does snore, but 6 just clicks........Scooby

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bigjay
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Post by bigjay » Sat Apr 23, 2016 11:28 am

I have tried ur method and afew others. it is well and truly in there!! is this a case of having to take the valve chest out ?? Thankyou. literally stood here scratching my head haha.

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bigjay
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Post by bigjay » Sat Apr 23, 2016 11:35 am

Ok ...amazing i just tried your theory again 'scooby ' soaked it thru so it wud swell when in the plunger left it for a few minutes and out she came ! brilliant . Thanku very much. Just polishing them up as we speak so fingers crossed. .....

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bigjay
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Post by bigjay » Sat Apr 23, 2016 12:34 pm

And nope, hasnt made any difference.... Any idea what to do now ?? Thanks .

DB770.DB880
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Post by DB770.DB880 » Sat Apr 23, 2016 5:07 pm

Inside the By-Pass valve it should have a 3/8 Brass Screw threaded into the valve with a Screwdriver slot, loosen off this screw, it has a hole in the center of it that you can fish it out with a piece of wire, then get yourself a 3/8 NF bolt screw it into the valve and pull out the By-Pass valve,
Hope this helps.

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bigjay
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Post by bigjay » Sat Apr 23, 2016 8:09 pm

Hi .... I managed to get it out in the end . cleaned all up and loader was still weak on pick up ... So just a bit lost with it now. Didnt really want to take valve chest out as dont really know what im doing with it as reguards to feed pipes , adjustments to spool valves etc.??
Anything i can do or check? Thanks guys .

DB770.DB880
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Post by DB770.DB880 » Sat Apr 23, 2016 10:31 pm

The first thing i would do, is take a Pressure reading, to see if It's the Hyd Pump or something else,
Do you have Remotes on this unit?

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bigjay
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Post by bigjay » Sun Apr 24, 2016 12:15 am

Remotes ?? Im not sure what they are but dont think so .

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bigjay
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Post by bigjay » Sun Apr 24, 2016 2:29 pm

I put weight on the back arms and they lifted 220kg like nothing so def not the pump im just baffled now what to do .... Altho that valve behind the bypass valve i couldnt lever down? literally snapped a screw driver trying . (Ooops) soaked it in wd40 ... Any help be greatfull what to do next. thanks

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ollek
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Post by ollek » Sun Apr 24, 2016 4:16 pm

The pressure needed to lift 220 kg on the lower links is not very much. The lift capacity at he ends of the lower links for a 990 with a pump that is not worn, is almost 1900 kg. A pressure of around 20 to 25 bar will lift 220 kg and the pump working pressure is in excess of 140 bar and the maximum pressure is even higher. Please measure the pump pressure first.

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