Mf 6490 hydraulic pump failure

[Cowabunga]

Early T2 6400 big chassis tractors [85 and up] had two hydraulic pump options. Both fed Bosch spools and both seemed to have load sensing external hydraulics and were plumbed for power-beyond, but none actually had the couplers for this, only stop-ends.

The two types were the high end option of CCLS with a variable displacement pump.
The other was a Twin Flow system with two fixed displacement gear pumps automatically combining flow [as opposed to later 5400 which have a blue switch that the driver decides to combine flow or not. The plumbing of the Twin Flow system is unknown to me and I've only ever seen two 6485 models fitted with it.

All gear pumps are prone to wear and seldom last more than 6000 hours in any tractor.

 

[Masseytinker]

I have a Massey 6180 (CCLS), booster pump inside left hand cover and piston pump inside right cover.
I have no steering. The lift operates, and I am getting 190bar pressure at the spool valves.
The Low pressure circuit is sitting too low at 13 bar, although clutch is working fine, PTO, diff and 4WD all operating normal, but strangely I am getting 0 bar pressure at the test point for booster pump. (Should be 5 bar).

I removed and checked the booster pump and its in perfect condition. I removed the test point for booster pump on R/H cover and alot of oil is flowing when tractor running so pump is pumping oil across. (sprayed oil across the yard).
There is a 5 bar safety valve in R/H cover, I removed cover to check the valve wasn't stuck open but it is also fine.

I've removed the orbital unit and its is fine, changed all 3 filters, checked both pumps. I've triple checked the spools in distribution valve blocks on R/H cover aren't sticking and also checked pump controller spools.

Anybody any ideas why I would be seeing no pressure at booster pump test point? (Digital guage is working-checked on another tractor).

 

[dee]

Does your tractor have a solid steel transfer pipe between the 2 pumps or 1 with a flexi joint in the middle of the pipe.

 

[Masseytinker]

It is a solid steel transfer between the 2 pumps. No flexi joint.

 

[Masseytinker]

Does your tractor have a solid steel transfer pipe between the 2 pumps or 1 with a flexi joint in the middle of the pipe.

Theres a view with R/H cover removed.
Do you know if the gear pump suction pipe which goes down into back end has a strainer or anything on the end of it?
Think I’ll need to take the LH cover off as well in order to get that suction pipe out to check if it is blocked at the end.
Theres nothing shown on hydraulic schematic.

 

[dee]

@DeeMc
The suction pipe has no filter on the end.

Could you remove the transfer pipe and take another pic of it please

 

[masseybreaker]

at the back where the gear wears a groove in it dee ?

 

[dee]

at the back where the gear wears a groove in it dee ?

From the picture I just can't make out if that is the old style transfer pipe that has the flexi joint in it.
Have you seen ones getting damaged by the 4wd gear

 

[masseybreaker]

had a few that have done it only thing i can think is that they turn somehow

 

[Masseytinker]

@DeeMc
The suction pipe has no filter on the end.

Could you remove the transfer pipe and take another pic of it please

Sorry only getting back to this now.
Have both pumps out. Attached some photos of the transfer pipe, there seems to be 2 pieces to it, the smaller piece is bonded into the bigger piece. It doesn’t look like it could be leaking. This pipe only goes to 5 bar pressure is that correct?
Don’t seem to have any restriction on the feed pipe to booster pump either.

 

[dee]

Yeah that's the transfer pipe on the 5 bar circuit.
That pipe is leaking you shouldn't have any rubber protruding on the joint.
Get yourself the modified pipe which is a solid steel pipe.
Try @masseybreaker he might be able to sort you with one

 

[Masseytinker]

Yeah that's the transfer pipe on the 5 bar circuit.
That pipe is leaking you shouldn't have any rubber protruding on the joint.
Get yourself the modified pipe which is a solid steel pipe.
Try @masseybreaker he might be able to sort you with one

Yea I’ll try get a new pipe for it.
Doesn’t seem like it would be leaking, think somebody may have used some kind of bonding glue on it in previous life, but I suppose 5 bar is a fair bit of pressure.

 

[Masseytinker]

Yeah that's the transfer pipe on the 5 bar circuit.
That pipe is leaking you shouldn't have any rubber protruding on the joint.
Get yourself the modified pipe which is a solid steel pipe.
Try @masseybreaker he might be able to sort you with one

Fitted a new 1 piece solid pipe and new washer on the flange end. Made certain all the pipes are engaging properly with the 2 pumps. Checked the O ring in the output port of the charge pump. New gasket on the charge pump cover intake.
Put all back together and still have exactly the same symptoms, no pressure on the 5 bar circuit. I put a fitting and pipe into the 5bar pressure test point on RH cover and ran the pipe into a bucket. Its pumping some oil full of the 3/8" pipe with no air coming, but it seems like low flow and I can almost block the end of the pipe. Is there anywhere else in this circuit for the flow to escape?

I can see nothing wrong with the charge pump- no wear on the casing at all, but I'm thinking I will need to go ahead and replace it regardless. I can turn the charge pump shaft easily enough when the LH cover is removed.

 

[dee]

There is a 5 bar relief valve on the r/h side plate (no.21)
Maybe it's stuck open dumping the pressure.

Failing that its looking like the charge pump must not be putting up pressure

 

[Masseytinker]

There is a 5 bar relief valve on the r/h side plate (no.21)
Maybe it's stuck open dumping the pressure.

Failing that its looking like the charge pump must not be putting up pressure

Took that 5 bar check valve out again to check it. Looks fine, not stuck open.
I've now put a new charge pump on, new seals, new transfer pipe, new gasket on charge intake.

Exactly the same problem, 0 pressure on 5 bar circuit.

Only possibility I can think of is if the O Ring seals on the ports of the main high pressure pump have blown out, allowing all the charge oil to escape. Do you think that could happen?

I'm like Putin in Ukraine, too far in now to turn back.

 

[dee]

Yes take a look at the o rings but the pump is a tight fit to the face of the side plate you would think there would be some pressure on the charge line.

 

[Masseytinker]

Yes take a look at the o rings but the pump is a tight fit to the face of the side plate you would think there would be some pressure on the charge line.

Took the R/H Cover off again. Took the piston pump off, the O-Rings look fine on its ports and pump as new condition.
With the R/H cover off I can see the transfer pipe between 2 pumps is in correct place and the suction pipe to new charge pump is in place.

Not sure where to go with this one now- can't figure out why I'm getting 0 pressure on the 5 bar circuit. The 5 bar relief valve in cover is definitely closed. Checked all the ports for blockages, or even cracks somewhere in the housing.

Is there any way I can rule out the Steering / Orbitrol unit causing any issue here? I had it apart a couple of times and it looks fine. I reset the "timing" on it as well (I've done this before plenty of times).

 

[dee]

Only way I can see to rule it out is try another orbital on the tractor as I'd be reluctant to blank off the pipes feeding it.

 

[box]

Bypass it with an inline ball valve between the two hoses, that way you don't have to block it off completely but it'll let you troubleshoot the circuit. It's not exactly the "safe" or "correct" way to do it though......maybe wear a tinfoil hat and some goggles.

 

[Masseytinker]

I've been chasing a red herring with this one i'm afraid- I couldn't figure out why had no 5 bar charge pressure. I was using a digital pressure clock, so got another standard 10 bar guage to double check the digital clock wasn't playing up. It also showed 0 bar. After a lot of head scratching I ordered another new 10 bar guage to triple check --- low and behold the pressure is sitting at 5 bar with the new clock!

So back to my original problem- Steering won't turn.
The 17 bar circuit is sitting at 13 bar.
Spool valve pressure gets up to 190 bar when pull spool lever.
Lift goes up and down.
If I hold a light force on the steering wheel, after about 7-8 seconds the steering will start to turn freely in either direction if I keep turning it. Once I stop, it goes stiff again.
If I try to turn the steering wheel and give the spool valve a pull at the same time, the steering will also start to turn.

High pressure filter has been changed several times, new oil. Orbitrol has been dismantled, timing checked, cleaned a few times.
Distribution block valves have been removed and checked for dirt / free moving.