'69 4020 3pt control valve leak

jd730des

Member
I have a '69 4020 and am chasing internal hyd leaks. Ive had my steering valve and both SCVs rebuilt by Tim Sweeney and now i think i have a leak in the 3pt control valve. I know i have problems with my hyd pump i'm pretty sure its lost output from 3 pistons. I am prepping to tear into it and need to know what to look for in the way of what is common to leak in the 3pt control valve and the brake valve-both are getting really hot when i plow and the 3pt pretty much wont lift the plow when the fluid warms up. Never been into either of these before so i appreciate any info before i tear into it.

Thanks
HB
cvphoto52181.png


cvphoto52182.png


cvphoto52183.png
 
Many thing can go wrong on a 3 point.
First, you need to know if your 3 point is sealing:

Put a heavy load on it (I mean something that will almost lift front axle), raise all the way. Then shut off and measure how long it takes to drop off. A perfect 3 point should not drop off. With a very haevy load, it would be OK that the 3 point dropps off in 5 min or so.

If the loads drops to quickly you can have (at least :D )
- Cylinder / piston / seal wear
- misadjustment of the valve
- Worn valve seats
- Thermal valve stuck or leaking
- Internal leak at the few orings between valve and cylinder

Then it can also seal but be constantly leaking oil at the inlet O-ring. But I would say that 90% of the rockshaft issues would make it seal poorly.

I assume external linkage + load control arm internal adjutment is already set per the manual? Doing so never hurts.
 
Many thing can go wrong on a 3 point.
First, you need to know if your 3 point is sealing:

Put a heavy load on it (I mean something that will almost lift front axle), raise all the way. Then shut off and measure how long it takes to drop off. A perfect 3 point should not drop off. With a very haevy load, it would be OK that the 3 point dropps off in 5 min or so.

If the loads drops to quickly you can have (at least :D )
- Cylinder / piston / seal wear
- misadjustment of the valve
- Worn valve seats
- Thermal valve stuck or leaking
- Internal leak at the few orings between valve and cylinder

Then it can also seal but be constantly leaking oil at the inlet O-ring. But I would say that 90% of the rockshaft issues would make it seal poorly.

I assume external linkage + load control arm internal adjutment is already set per the manual? Doing so never hurts.
 
Many thing can go wrong on a 3 point.
First, you need to know if your 3 point is sealing:

Put a heavy load on it (I mean something that will almost lift front axle), raise all the way. Then shut off and measure how long it takes to drop off. A perfect 3 point should not drop off. With a very haevy load, it would be OK that the 3 point dropps off in 5 min or so.

If the loads drops to quickly you can have (at least :D )
- Cylinder / piston / seal wear
- misadjustment of the valve
- Worn valve seats
- Thermal valve stuck or leaking
- Internal leak at the few orings between valve and cylinder

Then it can also seal but be constantly leaking oil at the inlet O-ring. But I would say that 90% of the rockshaft issues would make it seal poorly.

I assume external linkage + load control arm internal adjutment is already set per the manual?
 

Problem with 3 pt hitch could possibly be solved by following 3 pt linkage adjustment procedures outlined in 4020 tech manual.

I'm curious to know how you determined frt pump lost output of 3 pistons???? Did you disassemble pump?
 
You still have an internal leak starving the front pump, look in the fill hole with engine running if you see oil spraying you need to adress the hitch valve or components. Also check the standby pressure, should be 2250#
 
(quoted from post at 04:23:24 08/03/20)
Problem with 3 pt hitch could possibly be solved by following 3 pt linkage adjustment procedures outlined in 4020 tech manual.

I'm curious to know how you determined frt pump lost output of 3 pistons???? Did you disassemble pump?

Because i found pieces of the valve #23 in the pic lodged in the priority spool valve. Pump is making pressure but volume is decreased
mvphoto59651.png
 

I checked the pressure at the SCV and it is good, i am not getting good smooth flow from the pump- it is pulsing from what i believe is one or more grenaded valves in the pic below.
mvphoto59652.png
 

because the rockshaft control valve housing gets very hot along with the brake valve which indicates a high pressure fluid leak somewhere.
 

I found this description on another page and wondering what Oring he is describing-size of a pencil eraser?

[b:85fa454462]I had the same problem. Mine started while rolling hay. I lost power steering, lift arms and pressure to baler tailgate. I also had a whistling noise or fluid blow-by in the transmission. If you removed the hydraulic dipstick from transmission the noise was louder and you could see the fluid spraying inside the housing. I removed the rockshaft housing and also rockshaft piston and replaced all seals and o rings. Put everything back together and still had the same problem. [u:85fa454462]Then I removed the rockshaft contorl housing on right side of tractor and found one o ring the size of a pencil eraser that was broken. Replaced this [/u:85fa454462]o ring and fixed my problem. Hope this helps someone.[/b:85fa454462][i:85fa454462][/i:85fa454462]
 

I found this description on another page and wondering what Oring he is describing-size of a pencil eraser?

[b:393827618a]I had the same problem. Mine started while rolling hay. I lost power steering, lift arms and pressure to baler tailgate. I also had a whistling noise or fluid blow-by in the transmission. If you removed the hydraulic dipstick from transmission the noise was louder and you could see the fluid spraying inside the housing. I removed the rockshaft housing and also rockshaft piston and replaced all seals and o rings. Put everything back together and still had the same problem. [u:393827618a]Then I removed the rockshaft contorl housing on right side of tractor and found one o ring the size of a pencil eraser that was broken. Replaced this [/u:393827618a]o ring and fixed my problem. Hope this helps someone.[/b:393827618a][i:393827618a][/i:393827618a]
 

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