Hydraulic PTO issues ..... flow divider???

[Mechanos]

... but could there be a suction leak? Does your oil foam when it gets hot?

Hmmmm.... this has got me thinking.... and I do believe I have a way figured out to check (since there is no convenient "sight glass" to see the oil). However, I would think that if the oil was becoming entrained with air, it would affect the whole hydraulic system... not just one circuit. But I will investigate it anyway.

Sorry, I missed the schematic on post #5. In looking at that there is also the "Lube Relief" (Item 49) which is down stream of the delay relief. Assuming the schematic is drawn correctly this would also have some influence on PTO engagement pressure. I am not sure which one would have the most influence on actual operating pressure but I do know the company I work for sells lube reliefs in the 90 - 120 PSI range for ag and construction equipment. Some are even in 300 PSI range for larger high HP equipment.

I believe the best way to start eliminating possibilities is check the flow. If flow doesn't change and the pressure drops then you have a leak somewhere in the PTO circuit. If flow drops then you have a supply issue, pump, priority flow control or the flow divider, etc could be faulty.

Roy

The Lube Relief valve specification for my tractor is 6-11psi. I do not believe this would have an affect on my issue since when the main PTO valve is off, the Delay Relief Valve directs oil to the lube circuit. When the main PTO valve is on, the Delay Relief Valve shuts off oil to the lube circuit and directs it to the clutch/brake circuit. EDIT: wait a minute... that can't be true.... the oil still have to go somewhere. I re-read the theory and I was wrong on that. I guess the lube relief valve could affect things if it stuck open.

On another note, I talked to a different service tech today at the dealer and what immediatley popped into his mind was leaking clutch shaft or clutch piston seals.

Good thought on the flow.... I am trying to lay my hands on a flow meter.

 

[oldnslo]

The Lube Relief valve specification for my tractor is 6-11psi. I do not believe this would have an affect on my issue since when the main PTO valve is off, the Delay Relief Valve directs oil to the lube circuit. When the main PTO valve is on, the Delay Relief Valve shuts off oil to the lube circuit and directs it to the clutch/brake circuit.

Actually the delay relief just builds the pressure slowly and the oil should still be going to the lube relief once the clutch is engaged. When you engage the PTO it feeds oil through the orifice and pressure loads the spring chamber to increase the load to operate the clutch.

On another note, I talked to a different service tech today at the dealer and what immediatley popped into his mind was leaking clutch shaft or clutch piston seals.

Without doing any other diagnostics this is a good possibility.

Good thought on the flow.... I am trying to lay my hands on a flow meter.

Good luck

Roy

 

[Soundguy]

if the main scv's are seeing full pressure with oil hot.. then I don't think it is an oil or pump issue.. but rather what rickb mentioned earlier on page 1.. IE.. a leak int he circuit fo rthe pto clutch / brake..

soundguy

 

[Mechanos]

More testing tonight.... installed a thermometer on the oil filter to see what temp the oil is operating at. Oil temp ranges between 100 and 110 degrees... book says 110 is normal operating temperature.

I also intalled a hose with a gauge on the end to the transaxle lube test port to see what the lube relief valve is doing. With the PTO off, lube test port pressure is about 12psi.... book says 6-11psi. When the PTO is engaged, the pressure at the lube relief port drops to 0. I'm not sure how the oil is returned to the tank when the PTO is engaged, but it does not appear to be passing the transaxle lube test port.

I let the tractor run at 3450 RPM and engaged the PTO. I let the tractor run until the pressure in the PTO circuit fell off to the point where the PTO disengaged. I then shut the tractor off and quickly removed the gauge from the end of the hose on the transaxle lube test port and routed the free end of the hose up to the transaxle fill port. Restarted the tractor and engaged the PTO lever to verify that the PTO would not engage. Then I disengaged the PTO lever and quickly drew a sample of oil from the free end of the hose attached to the lube test port in a clear plastic cup. Then shut the tractor off.

Looking at the oil in the cup againt a strong work light revealed that the oil if full of gazillions of tiny air bubbles. I let the cup of oil sit for a few minutes while I tinkered with other things and rechecked it. Clear as a bell.... no bubbles left after a few minutes. Restarted the tractor (oil is still warm at this point) and the PTO would engage for a little while, but again disengaged as the pressure dropped in it's circuit. This tends to support the theory that it is air in the oil and not related to oil temperature.

So I think I'm onto something here. As suggested by Stonehaller, there may be a suction leak. I can't think of any other way the oil would become entrained with air. These two couplers pictured below are my most likely culprits:

 

[dfkrug]

(original 33hp engine was replaced with a 37hp engine).

Did you mention that before?

It is a testament to the reliability of the x55s that there has been little
written on TBN about failed PTO clutch and brake systems. I never
had any of mine apart at all.

Those rubber manifolds that JD uses on the suction lines are a good
source of pinhole leaks, as you noted.

 

[Mechanos]

I guess I'll try replacing those rubber pieces next. Afterall, they are 20 years old. The lower one is pretty cheap, but the upper 3-pronged one is $52.

 

[oldnslo]

More testing tonight.... installed a thermometer on the oil filter to see what temp the oil is operating at. Oil temp ranges between 100 and 110 degrees... book says 110 is normal operating temperature.

I also intalled a hose with a gauge on the end to the transaxle lube test port to see what the lube relief valve is doing. With the PTO off, lube test port pressure is about 12psi.... book says 6-11psi. When the PTO is engaged, the pressure at the lube relief port drops to 0. I'm not sure how the oil is returned to the tank when the PTO is engaged, but it does not appear to be passing the transaxle lube test port.

If there is no lube pressure at this time you are potentially damaging the components that are supposed to be getting lubed.

I let the tractor run at 3450 RPM and engaged the PTO. I let the tractor run until the pressure in the PTO circuit fell off to the point where the PTO disengaged. I then shut the tractor off and quickly removed the gauge from the end of the hose on the transaxle lube test port and routed the free end of the hose up to the transaxle fill port. Restarted the tractor and engaged the PTO lever to verify that the PTO would not engage. Then I disengaged the PTO lever and quickly drew a sample of oil from the free end of the hose attached to the lube test port in a clear plastic cup. Then shut the tractor off.

Could you see into the tranny to see if it was also full of air bubbles?

Looking at the oil in the cup againt a strong work light revealed that the oil if full of gazillions of tiny air bubbles. I let the cup of oil sit for a few minutes while I tinkered with other things and rechecked it. Clear as a bell.... no bubbles left after a few minutes. Restarted the tractor (oil is still warm at this point) and the PTO would engage for a little while, but again disengaged as the pressure dropped in it's circuit. This tends to support the theory that it is air in the oil and not related to oil temperature.

So I think I'm onto something here. As suggested by Stonehaller, there may be a suction leak. I can't think of any other way the oil would become entrained with air. These two couplers pictured below are my most likely culprits:

View attachment 178872View attachment 178873

 

[JohninCT]

Any possibility that you're PTO selector valve is leaking by causing enough pressure loss to the tank return which causes the DRV to shift and disengage the clutch?

 

[Mechanos]

...Could you see into the tranny to see if it was also full of air bubbles?

No way to see into the transaxle.... that is why I had to use the hose and a clear cup to extract a sample.

 

[Soundguy]

At first I simply thought about a leak at the pto valve.. but the air bubbles thing.. it's deffinately getting in on a suction side.. not on a pressurized leak / side.

soundguy