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990 trouble with 3 point

Posted: Thu Jun 20, 2019 4:26 am
by DB990Toby
Hello, first post. Thanks for allowing me to join.

I have a DB990, bought it in 1996, been using it on the farm ever since, although now we use it mainly as a raking tractor during hay season, plus a few other regular duties, such as running the 3 pt. mounted fertilizer spreader on the fields in the spring.

It was during this work a few weeks ago that the 3 point hitch would not lower when I pulled in to refill the hopper (was working normally until then)
I made do in order to finish the job and now have the tractor in my shop.

I got the arms to lower by removing the cover on which the locking latch is mounted. All reassembled, with the arms down.
Now the arms won't go up.
The locking latch works (locks, unlocks) when I pull up the lower arms by hand
There is plenty of oil (transmission/hydraulic)

The only thing out of the ordinary that I did was to remove the hydraulic hoses and front end loader controls, since we don't use them anymore.
The hoses were connected to the hydraulic block to the right of the operator's seat.
I removed the hoses and plugged the openings with OR-B bolts.

Anyone know whats wrong here?

EDIT:
The tractor is a David Brown Case, circa early 1970's, and Selectamatic I believe.

Re: 990 trouble with 3 point

Posted: Thu Jun 20, 2019 5:22 am
by cobbadog
Re connect your hoses and see if it works again. If so there is a plumbing issue in the way it was plumbed up.

Re: 990 trouble with 3 point

Posted: Thu Jun 20, 2019 7:54 am
by ollek
Can you please supply a picture showing the block and the plugs you are talking about. Sounds like the front loader valve has been connected in series with the tractor hydraulics, using a series connection plate on top of the double acting valves ( if the tractor has double acting valves). If this is the case, then the oil from the pump to the valve chest is now blocked with the plugs you have fitted. The original top plate has a passage inside the plate for connecting the pump flow to the valve chest. You will have to connect the two connections for the loader valve together with a short hose in order to get the oil to the valve chest or find a original top plate from a tractor without a front loader. Do not use the tractor before the 3-point hitch is working, as blocking the oil flow will make the main relief valve blow off and lead to serious wear of the hydraulic pump. What I have said is based on assuming that the tractor has a series connection plate and a double acting valve, but a picture is needed to confirm this. Double acting valves was not standard fitment in those days, but different countries had different specifications. The series connection plate was never fitted at the factory, but was made locally and then fitted by a David Brown / front loader fitter or the tractor owner himself. Many different series connection parts have been made by different people and it is impossible to know the setup without seeing a picture.

Re: 990 trouble with 3 point

Posted: Thu Jun 20, 2019 3:39 pm
by DB990Toby
Thanks Cobbadog and Ollek. Those are very sound suggestions.
I will get some pics loaded tonight.
Cheers, Toby

Re: 990 trouble with 3 point

Posted: Fri Jun 21, 2019 7:45 pm
by 1952CROPMASTER
Hi Toby;
What part off Canada are you from?

Re: 990 trouble with 3 point

Posted: Sat Jun 22, 2019 5:51 am
by DB990Toby
Cannot figure out how to post a picture, sorry.
As a new member, I may be blocked?

I took a couple pictures, had my wife email them to me, all good.
I could probably email them to someone if necessary.

I am assuming that the 3 point problem I have is as was suggested by ollek; that I inadvertently blocked hydraulic flow.
On that premise, I had a short hydraulic hose made up today at Princess Auto, I plan to remove the
ORB plugs and install the new hose, should fix it (fingers crossed)

1952Cropmaster: I am located in North Central B.C.

Thanks all.

Re: 990 trouble with 3 point

Posted: Sat Jun 22, 2019 6:40 am
by philedge
If you click on "board index" at the top left of the page, theres a couple of posts that tell you how to handle photos.

Re: 990 trouble with 3 point

Posted: Sun Jun 23, 2019 5:04 am
by cobbadog
you must compress the images before posting.

Re: 990 trouble with 3 point

Posted: Sun Jun 23, 2019 3:28 pm
by DB990Toby
Problem I have is in transferring the pictures from incoming email to a format that I can access.
We are going to work on that.

Meanwhile, I installed the new hose, connecting the two circuits I had previously plugged;
three point works normally again.

Thank you for the advice.

Re: 990 trouble with 3 point

Posted: Sun Jun 23, 2019 4:36 pm
by ollek
You wrote "connecting the two circuits I had previously plugged". There is not two circuits, but you have blocked the circuit from the pump to the valve chest by fitting the plugs. The hose you now have fitted acts in the same way as the loader valves, letting oil to the valve chest. The hydraulic circuit is originally as follows: Pump - plate with internal oil channel on top of the double acting valves -double acting valves- doubler acting valve(s) valve chest. When fit a loader with separate valves, you plumb the system to the following: Pump - front loader valves - serial pate on top of double acting valve(s) - double acting valves - valve chest. To do this you have to remove the original top plate and fit a locally made serial connection plate for oil supply to and return from the loader valves.

Re: 990 trouble with 3 point

Posted: Mon Jun 24, 2019 5:24 am
by DB990Toby
Hi Ollek, thank you for the clarification. I understand what you are saying, that it is actually only one circuit.

The 990 has been a very good machine for us, we have maintained it well of course, but only minimal repairs
have been required in 23 years of ownership.

It was our sole tractor until 2003, but continues to fulfill a role on this farm every spring and summer.