3 pt will drop when engine is turned off and load is on 3 pt. When I start engine the 3 pt will lift blade but pulsated up and down an inch or two. Shut off the engine and the lift drops slowly and I hear a clicking noise from the area of the relief valve. What could cause this problem?
CCWKen
Veteran Member
- Joined
- Mar 22, 2005
- Messages
- 1,199
- Location
- South Texas, USA
- Tractor
- Ford-3910, JD-420C, Kenbota-Custom, IH-2606
Doesn't sound like you have a problem. Is the pulsing on idle or when throttled up? If on idle, it's normal.
JC-jetro
Elite Member
Howdy,
Since the 3 point system is able to lift the load I can cautiously say that you do not have a pumping issue. I start with what you suggested in your post.
1.Your relief valve is bleeding by due to valve seat being worn out or contamination. That can only effect the pressure that your pump can develop and nothing else.
2. The spool valve in "open center" hyd system is the only way hyd oil/ pressure can be relived back to the reservoir. if the check valve in the spool can not hold the pressure causes the arms to drop.
I would first check the follwing before anything else.
-lift piston seal is leaking by. pretty simple to replace $10 and 1 hr tops labor if you do it yourself.
-shock load relief mechanism check valve in the lift piston head is leaking back to reservoir all the time with the pump catching up with the rate of the leak. very easy to check. if you need additional info I can post pertinent pics to help later.
JC,
JC, Thanks for the info. From what I read in your post the relief valve probably is not the problem, correct me if I have misinterpreted this. I will have to read up on how big a job it is to replace the lift piston seal and what to do if the shock load valve is leaking. Do these two items need to be fixed at the same time while the housing is disasembled? Ray
CCWken. Pulse is less when RPM are high. I have never had this problem before the lift started dropping after engine shuts off. I am concerned the pump will not be able to overcome the drop while I am grading the driveway with box blade on. I have had this tractor since bought new. Pressure is leaking down, I think JC is leading me in the right direction for repair. All suggestions are appreciated.
JC-jetro
Elite Member
ray,
Relif valve just regulate the pressure from discharge side of the pump before it enters the lift spool valve. It can relive pressure in to the reservoir (ie. rear differential) before entering the spool valve. it is not much of a fix on them other than inspection to find the cause. I have got several post that explains it in details. there are 3 things you need to inspect with piston seal to be the last.
1) Relief valve to clean and inspect.
2)shock load relief mechanism at the lift piston head.
hole in the middle is supply to the lift piston and the rate of drop needle valve. Second hole from the right is normal checked valve flow to the lift piston. flow can not go back from the second hole(check valved) hence making the middle hoe only way the flow can be returned to the reservoir and having an ability to regulate it by an external knob. The 3rd hole (3rd from right) is the shock relief that relives the oil from outside of the cylinder directly in to rear diffy when you carry a heavy load on 3 point and hit some obstruction.
The first stiff spring and the ball act as shock relif, clean and check for the roundness of the ball.
3) Lastly, check the lift piston seal and change if necessary. The way mine looked after 28 years. easy to replace.
Piston with a new seal install. There are two fat o-rings that seal the piston to the cylinder and the head. most likely you will not need to change them unless they look bad.
JC<
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JC-jetro
Elite Member
No, You will open it as the pics below suggest. Only open the outer bolt , stiff spring and first small ball for inspection. Take a flashlight and look at rust pitting on the valve seat.
JC,
The stiff spring and valve is between the fist and the second bolt. it will not hurt but you only need to loosen the most outer nut.
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I checked the relief valve and the shock valve both looked good except the relief valve had a bright ring around it where it seals in the seat like maybe it viabrates some of the time. Do you think the pressure tension might be to light and need adjusted? I have my box blade attached which weighs about 400 lbs.
JC-jetro
Elite Member
The only way you can do that to put 3000 psi liq filled pressure gauge on the cylinder head, raise 3 point with no load and continue to raise where the relief starts to chatter and relive, that would be your pressure setting. I think it should be around 2300 psi. notice that you do not have shims behind the spring to adjust but can change the spring tension by adjustment nut provided. All of that said it can nor explain 3 point dropping. my two other options would be to check the piston seal and lastly your 3 point spool valve. I'd exhaust all before I tackle the spool valve.
good luck,
JC,
