990 hydraulic issue

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DB990Toby
Posts: 10
Joined: Wed May 15, 2019 8:17 am
Location: Canada

990 hydraulic issue

Post by DB990Toby » Fri Jul 26, 2019 5:26 am

Hello, I received assistance here recently with some 3 point problems on my 990 (thanks again)
That has been resolved, now we have another issue;

What I assume is a relief mechanism attached to the front of the 'hydraulic block'
Inside of this removable part are various parts, including a coil spring.
It is open on the front, a small washer complete with a very small hole is held in by an internal snap ring

This device has taken to spurting hydraulic fluid through the hole in the washer when the actuation lever is operated in order to raise or lower the attached implement
(in this case a rotary hay rake, operated by a single hydraulic line plugged into the tractor remote via a Pioneer quick connect coupler)
I have had this ( relief valve ? ) apart, can't see any sort of seal or O ring to replace.

I have had this tractor for many years, had lots of different implements connected to the remotes (which I installed many years ago)
A bit of oil has always dripped from this part, but not spurted vast quantities like today.

Tried to attach a picture, apparently the file is too large.
IMG_20190725_191538 (600x800) (480x640).jpg
IMG_20190725_191538 (600x800) (480x640).jpg (202.22 KiB) Viewed 848 times

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ollek
Posts: 3816
Joined: Tue Apr 10, 2012 1:20 pm
Location: South West Finland

Re: 990 hydraulic issue

Post by ollek » Fri Jul 26, 2019 11:35 am

Have a look in the following link showing the parts for the double acting valve kick out system https://partstore.caseih.com/us/parts-s ... 1ar1289890 The O-rings involved are shown in this link. The front end of the valve is not a relief valve, but a system that moves the main spool to mid position when the pressure in the hoses gets over a present figure. This happens when for instance a cylinder reaches its full stroke and the piston bottoms out.

tomryall
Posts: 148
Joined: Sun Jun 03, 2007 4:53 am
Location: canada

Re: 990 hydraulic issue

Post by tomryall » Fri Jul 26, 2019 3:35 pm

These cessna valves are double acting, if you are using it to operate a single acting ram then you will have back pressure when you lower the implement .
you really need a dump line from the second pipe on the Cessna valve to the gearbox. I have these valves on my DB' and that is how I use them on single acting rams. I don't know of any way to convert them to single acting.
Where in Canada are you , send me a pm

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ollek
Posts: 3816
Joined: Tue Apr 10, 2012 1:20 pm
Location: South West Finland

Re: 990 hydraulic issue

Post by ollek » Fri Jul 26, 2019 4:15 pm

Never connect the return directly to the gearbox on a David Brown tractor. The return has to be connected to one of the plugs provided, or the gear box lubrication will be effected. In stationary use the gear box will be damaged do to starvation of lubrication oil if the return is directly into the gear box and the double acting valve lever is left in lowering position. There is an other topic, called 1490 hydraulic return/dump on this forum at the moment, dealing with the hydraulic return points. You can convert a double acting valve to single acting by connecting the lowering port to one of the return plugs. The return must always be connected to the gear box lubrication piping. The OP was not asking about the valve setup, but he has a problem with oil leak from the kick out mechanism.

DB990Toby
Posts: 10
Joined: Wed May 15, 2019 8:17 am
Location: Canada

Re: 990 hydraulic issue

Post by DB990Toby » Fri Jul 26, 2019 6:10 pm

Thanks guys. Good information but I'm still in the dark.
Just need a quick fix to get the tractor back out in the field, we are close to finishing the hay harvest between rain showers.
Two more hours of raking and the DB can sit waiting for a proper repair.

Sounds like I need to figure a way to allow oil to return to the system when the rake is lowered.

Regards, Toby

1952CROPMASTER
Posts: 95
Joined: Thu Dec 15, 2016 12:24 pm
Location: Moncton NB

Re: 990 hydraulic issue

Post by 1952CROPMASTER » Sun Jul 28, 2019 1:28 am

Hi Toby;
What part of Canada are you in,

DB990Toby
Posts: 10
Joined: Wed May 15, 2019 8:17 am
Location: Canada

Re: 990 hydraulic issue

Post by DB990Toby » Sun Jul 28, 2019 7:38 am

1952Cropmaster: We're near Prince George B.C.

Temporary fix: We piped the relief to an oil can in order to finish raking before the rain hit, success!

So based on the advice received here my 990 is equipped with a double acting valve, our new rake has only one hydraulic line so when raising or lowering the rake the oil has to travel back and forth in the same line.
I can see why this could be a problem but;

I don't understand why we have not had this issue before with single hydraulic line implements i.e. one of our old hay rakes (may it r.i.p.)
has a single line, used it with the 990 for many years, no problem with oil squirting out the relief.

Does it simply need a resealing kit in the actuator?

As mentioned I installed 2 remotes years ago, seems obvious that the currently unused one could be used as the return.

Any suggestions on how to convert the single line to connect to both the supply and return on the tractor?

Regards.

User avatar
ollek
Posts: 3816
Joined: Tue Apr 10, 2012 1:20 pm
Location: South West Finland

Re: 990 hydraulic issue

Post by ollek » Sun Jul 28, 2019 9:31 am

I have said before and I will say it again, there is no relief valve in the double acting valve. The front end in the double acting valve is a system that returns the valve spool to mid (hold) position when the pressure in the working line reaches a pre set figure, normally around 130 bar. The system keeps the spool in operating position and the spool will return to centre position when pressure set is reached. This will happen it you do not hold the lever in working position, but let your hand off the lever once the spool is in operating position. This is called automatic kick-out. The reason for the oil leak is leaks at the O-rings and I have supplied a page from the parts catalogue in an earlier post. The pressure in the system is not the reason for the oil leak, but one or several O-rings can get damaged if the valve lever is constantly kept in a dead end position (full pressure constantly acting on the kick out mechanism). The reason for the oil leak is, as said, damaged O-rings and nothing else. Disassembly the double acting valve and change all O-rings shown in the picture. You wrote: "seems obvious that the currently unused one could be used as the return". Both valves have pressure and return. When one outlet is pressurized for moving a double acting cylinder in one direction, the cylinder moves and the oil from the other side of the piston has to be directed back to tank. When the other outlet is pressurized then the first mention outlet becomes a return to tank. This changes between the outlets depending on witch way you move the operating lever. This is called double acting. The simplest way to convert a double acting valve to single actin is by connecting the port under pressure when the cylinder is lowering, to the transmission lubrication circuit using a suitable hose.

DB990Toby
Posts: 10
Joined: Wed May 15, 2019 8:17 am
Location: Canada

Re: 990 hydraulic issue

Post by DB990Toby » Sun Jul 28, 2019 7:32 pm

Thank you for your patient explanations Ollek and tomryall, it is sincerely appreciated.
If I repeat myself it is because I do not have a clear understanding of how this system on the 990 works.
On reading your answers I now feel I have a clearer comprehension of the working of these hydraulics.

I did look into the link for Case/IH parts provided by Ollek, and found article #23, which is a seal kit.

With that information I can now confidently order that seal kit, knowing that it (should) solve the problem.

Interestingly, I have accessed that site before, in seeking parts for our International 620 seeder, which is approximately
the same vintage as the DB-990

Regards
Toby

tomryall
Posts: 148
Joined: Sun Jun 03, 2007 4:53 am
Location: canada

Re: 990 hydraulic issue

Post by tomryall » Sun Jul 28, 2019 8:23 pm

when you take off the end cap to replace the seals you will find three small balls inside the cap[be very careful removing this or you might loose them] you can leave out these balls if you want, the only difference is that the lever will not stay locked until the ram reaches the end of its stroke, I found this works better for some jobs. the lever will return to neutral on letting it go .
Tom

DB990Toby
Posts: 10
Joined: Wed May 15, 2019 8:17 am
Location: Canada

Re: 990 hydraulic issue

Post by DB990Toby » Tue Jul 30, 2019 6:30 am

Cheers tomryall.
I noticed that there was a place for 3 balls when I last had it apart, but there were none.

Regards, Toby

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