780 Control Valve

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amck
Posts: 24
Joined: Mon Sep 23, 2019 4:53 pm
Location: Northern Ireland

780 Control Valve

Post by amck » Wed Nov 06, 2019 9:36 pm

Hey guys need your help.

Recently bought a 780 which the back bars don’t lift, from the troubleshooting the bypass valve needed cleared although someone had been there before.

So valve out all ok nice and free, cleaned with air and a new nylon filter back together and oil is still just flowing and no lift.

From the manual and the case diagram website I thankfully received there is meant to be two springs. Now someone had placed a spring under the dump valve which I don’t believe is right (am I correct) and only one spring on top of the bypass valves.

Now am I correct in saying both these springs should be on top of the bypass valve which is then the next problem how to get them compressed down in there. I have attached a photo of the springs. Are these the correct springs?

Thanks

amck
Posts: 24
Joined: Mon Sep 23, 2019 4:53 pm
Location: Northern Ireland

Re: 780 Control Valve

Post by amck » Wed Nov 06, 2019 9:38 pm

Photo of 1 of the springs
Attachments
93E60EDF-1456-4371-A952-D68F1C51F9DE.jpeg
93E60EDF-1456-4371-A952-D68F1C51F9DE.jpeg (76.83 KiB) Viewed 178 times

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ollek
Posts: 3837
Joined: Tue Apr 10, 2012 1:20 pm
Location: South West Finland

Re: 780 Control Valve

Post by ollek » Thu Nov 07, 2019 3:33 am

Yes there is 2 springs, one on top of the by-pass valve and one on top of the hold valve. Both springs are the same. If the tractor has a dump valve, then this valve is fitted in stead of the plug on top of the spring in the hold valve and there have to be a spring under the dump valve, same as in the by-pass valve. Please see the following link https://partstore.caseih.com/us/parts-s ... 03ar292683 The drawing does not show a spring on top of the hold valve, but the text show there is 2 springs in the system. This is how parts catalogues are constructed, not all parts are always shown, but the text tells you how many parts with the same part number is used in the system. The person that uses the parts catalogue must have a knowledge of how the system is constructed. Is the tiny hole (diameter 0,5 mm) in the restrictor on top of the nylon filter open? The small nylon filter (screen) is washable and do not need to be changed if it is not damaged. Does the spool valve drop fully down (washers must get tight between the nuts and the valve chest body), when the operating lever is pulled fully back? There is nothing called "back bars" in the tractor. The 3-point hitch have 2 lower links and a top link. Please see the following link https://partstore.caseih.com/us/parts-s ... 03ar321119 and also the following link https://partstore.caseih.com/us/parts-s ... 03ar319708

amck
Posts: 24
Joined: Mon Sep 23, 2019 4:53 pm
Location: Northern Ireland

Re: 780 Control Valve

Post by amck » Thu Nov 07, 2019 5:56 pm

Thank you for the advice done as described and the lift is one again lifting the lower links. Probably is it doesn’t want to stop lifting the lower links. Any ideas where to go next. It will lower again if level is fully forward with weight on them. Thanks.

User avatar
ollek
Posts: 3837
Joined: Tue Apr 10, 2012 1:20 pm
Location: South West Finland

Re: 780 Control Valve

Post by ollek » Thu Nov 07, 2019 6:18 pm

I think you have the selector switch in the TCU position. Please select height (position) control. It you do not know how to do the selection or what draft, height and TCU means, please get yourself a Operators Manual. To get a manual, use the following link http://www.davidbrownparts.com/Books%20 ... nuals.html

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