1212 Hydraulic problems

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oldtractorman
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Joined: Sat Mar 17, 2018 9:12 pm
Location: somerset

1212 Hydraulic problems

Post by oldtractorman » Fri Mar 23, 2018 2:13 pm

Am having a problem with a 1212. Hydraulic pressure from spool valve is around 2100 psi and works fine However lift arms are slow to lift and jerk up and down when oil is warm. Testing the pressure on the external trailer coupling only gives a reading of 1200 psi so obviously something not right. Have cleaned and checked the hold valve and the bypass valve but all looks good with them including the little gauze in the bypass. Any help with this will be much appreciated

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ollek
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Re: 1212 Hydraulic problems

Post by ollek » Fri Mar 23, 2018 4:18 pm

Have you checked that the small hole in the centre of the hold valve tip and the hole in the restrictor washer in by pass valve are open?

oldtractorman
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Location: somerset

Re: 1212 Hydraulic problems

Post by oldtractorman » Mon Mar 26, 2018 6:46 pm

Thanks for your reply Yes I have and all seems to be clean Cant understand why the pressure is so low coming out of the valve chest quess will have to take out valve and investigate a bit deeper

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ollek
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Re: 1212 Hydraulic problems

Post by ollek » Tue Mar 27, 2018 1:16 pm

You have a problem with the hold position if the linkage is jerking up and down. The reason for this can be one or several of the following: Leaking hold valve, leaking O-ring between valve chest and internal pipe supplying oil to the external pipe going to the lift cylinder, cracked internal pipe, leaking lift cylinder. You can test the lift cylinder in the following way. Lift a load (more than 100 kg) to almost full height. Then select position 2 on the 3-way valve and stop the engine. The hitch will slowly lower if the lift cylinder is leaking. The lift cylinder is OK if the linkage do not lower.

oldtractorman
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Joined: Sat Mar 17, 2018 9:12 pm
Location: somerset

Re: 1212 Hydraulic problems

Post by oldtractorman » Tue Mar 27, 2018 9:55 pm

Thanks once again for your reply Have raised lift arms and shut off via vale and no drop so no leakage on ram cylinder. Have had handbrake off to look in from front and can see no leakage from the double pipe on front of valve chest. When looking through back cover there is a good oil supply running out which stops when moving lever to lift position. Will have a look again tomorrow at hold valve and check spool valve is moving okay

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ollek
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Re: 1212 Hydraulic problems

Post by ollek » Wed Mar 28, 2018 5:03 am

An oil stream, that looking from the rear, stops when moving the control lever to the lift position, shows that the by pass valve is closing, and that the oil stream is diverted to the double pipe and from there to the lift cylinder. The spool valve have to move fully down for the by pass valve to close, suggesting that the spool valve is working OK. This is how the system works. Please remember that an leaking (external or internal) dump valve will result in a leaking hold valve, loss of hold position and possible pressure loss in the lift cylinder.

oldtractorman
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Location: somerset

Re: 1212 Hydraulic problems

Post by oldtractorman » Wed Apr 04, 2018 9:49 am

Thanks for your help I have now tried dropping the link arms with engine stopped and bypass valve removed and oil flows from bypass orifice as arms drop. Looking at other info on this site it seems to indicate problem with oneway valve . If this is correct presumably the valve chest has to be removed to rectify this?

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ollek
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Re: 1212 Hydraulic problems

Post by ollek » Wed Apr 04, 2018 11:56 am

A leak at the non return valve will only result in loosing the hold position (linkage starts to hiccup) but it will not lead to low lift pressure. You need to remove the valve chest if you want to get to the non return valve. A leaking by pass valve will lead to low lift pressure, but have no impact on the hold position. A leaking hold valve, or a dump valve, will effect the hold position and can also reduce the lift pressure.

oldtractorman
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Joined: Sat Mar 17, 2018 9:12 pm
Location: somerset

Re: 1212 Hydraulic problems

Post by oldtractorman » Wed Apr 04, 2018 9:54 pm

Okay many thanks for your reply you have been most helpful. Good to know what effect each valve will have on the system if faulty. Will have to get the valve chest out and investigate sometime if it ever stops raining here ! Thanks once again you have been brilliant

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