Power Trac 418 Tire fell off!!!

   / Power Trac 418 Tire fell off!!! #11  
I am going to have to disagree to the valve holding ability.

If they all leak down, that is the manufacturer specification and I would call that an inferior valve.

If that were used on a job regulated by OSHA, they would ban that machine.

I certainly did not purchase my PT just for an inferior valve. That is not a feature anyone would want.

Excerpt:

If the hydraulic equipment has a leak (either internal or external), the performance efficiency will be directly (and dramatically) affected. For example, if the designed cycle time of an hydraulic circuit is 3 seconds, but the leakage causes the cycle time to slow to 6 seconds, the result will be reduction in performance efficiency of 50%.

Hydraulic System Leakage - The Destructive Drip

Now, you all can say that is the way it is, but you don't have to accept that.

If for example the avg leak down rate for most hyd sys is 10 drops per minute, and most manufacturer will replace a valve that leaks more than that under the warranty.

Then along comes the valves from PT, with a leak down rate of greater than 20 drops per minute.

Under the warranty, you have to live with their specs, but after the warranty is gone, you either live with it or replace the valve with a know good quality valve.

The PT loader valve is not that special.

I am surprised that Terry would say such a thing, like that is the way PT wanted it. We want a leaky valve so the lift arms will be on the ground ready to work.

Maybe the mining machines had it that way so they would not forget and run into the mine with the loader up.

I say, if you have a loader or any hyd, that is not to your liking, then fix it.

I doubt that PT has ever replaced a loader valve.

I removed my loader valve and had it tested to eliminate the leak down, and they said it was good.

At that time I did not know about the drops per minute, so I don't know if they did that kind of test.

I have no idea of the guide lines used in hyd shops as to testing for a go or no go on hyd components.

I am not even sure they test things they fix.

Have you ever seen a tag on a piece of equipment saying tested at 100 %. Meaning the pressure was good, and there was no leakage for 5 min at max pressure.
 
   / Power Trac 418 Tire fell off!!! #12  
The way it was framed up to me was that it was a choice between managing cylinder and hose failures due to thermal expansion and contraction versus allowing a minuscule amount of internal valve bypass. Call PT if you like, but I believe that they can supply check valves that have no internal bypass and therefore have zero leak down. My impression was that if one goes that route, one has to be careful never to leave a cylinder fully retracted or fully extended to prevent overpressure failures or vacuuming dirt/water into the system.

Personally, I can see logic to both sides. My own use of hydraulics is never to leave them in states where a failure might cause injury. So, my own personal standard operating procedure is to put the arms on the ground, power the machine off and cycle the valves to release pressure in all of the circuits. That way, I can walk away from the machine without being concerned about it being in a hazardous state, or as unhazardous a state as 20 gallons of oil and 10 gallons of diesel sitting next to a battery can be.

BTW: the leak that the link article is talking about is leak out of the system. I believe that the leak down under discussion here is leakage within the hydraulic system, e.g. bypass or bleed. I'm totally against leaks out of the system. I have even plumbed the breather on my automatic brakes back to the tank to capture the couple of drops that emerge from each cycle of the brakes. (Kit from PT)

Make it a great 4th!

All the best,

Peter
 
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   / Power Trac 418 Tire fell off!!! #13  
When my LS was fairly new, it got a leak in the fuel tank and I was anticipating getting the dealer to pick it up but with a dry tank I didn't want to put fuel in it just to load it so I put the loader full up. It sat for over 2 weeks and only leaked down about half way. The rear 3 PH will stay up forever without any leak down. My Kubota FEL will leak down overnight and I have never timed it to see if it is 3 hours or 12. The backhoe leaks down pretty fast from every cylinder and I will have to hit the stabilizer lever after about 10 minutes to get it to level up. The boom will leak down in 10 minutes also unless it is locked in place. I guess it is just cheap valves or maybe cheap cylinder seals or both that Kubota uses. Maybe the get them from the same place PT gets theirs.
 
   / Power Trac 418 Tire fell off!!! #14  
Well, facts is facts.... all PTs leak down from the factory since at least my 2001 model year.

As for me, I too never leave it in a state where a leak-down could occur. I always lower the implement to the ground, power it off and put it in float for good measure. This is a habit from my snow plowing days. The operator's manuals of the plows all said to lower the plow anytime you leave the operator's station to avoid serious injuries or death.

My feelings are you should never leave something with stored energy if at all possible. For example, leaving the FEL arms up and getting off the tractor and then having something bump the joystick could cause the FEL to drop.
 
   / Power Trac 418 Tire fell off!!! #15  
Well, facts is facts.... all PTs leak down from the factory since at least my 2001 model year.

As for me, I too never leave it in a state where a leak-down could occur. I always lower the implement to the ground, power it off and put it in float for good measure. This is a habit from my snow plowing days. The operator's manuals of the plows all said to lower the plow anytime you leave the operator's station to avoid serious injuries or death.

My feelings are you should never leave something with stored energy if at all possible. For example, leaving the FEL arms up and getting off the tractor and then having something bump the joystick could cause the FEL to drop.
Pretty much how i leave my PT, engine off, FEL in float.
 
   / Power Trac 418 Tire fell off!!! #17  
Here is the main reason that the lift cyl will drift down even if the lift cyls are good.

Excerpt:

Most hydraulic valves are a metal-to-metal fit spool design, so do not depend on the cylinder setting dead still with a tandem center spool. If there are outside forces on the cylinder, it will creep when the valve centers.

Any metal-to-metal fit spool valve never fully blocks flow. With external forces working on the cylinder, it may slowly creep with the valve centered.



Well, you have the outside forces with the weight of the lift arms. Then add leaky cyl and down it drops before your eyes.

What does the metal to metal contact tell you about the leakage. Spool tolerance to bore tolerance.

It speaks to the quality of the hyd components a manufacturer wants in their machines.

They can brag about tight tolerance, but do you think the would brag about loose tolerance.

However, some of you say PT brags about how they really wanted valves that leak more than other valve competitors.

Their reasoning, is not valid.

They could say, they were purchased on price alone, and that might be true.

Need I say more, you have the facts.

My loader arms leak down over night, but if I need better, I have some needle valves that can be used.

If it leaks down after that, it has to be the cyl seals.
 
   / Power Trac 418 Tire fell off!!! #18  
My recollection was that they were concerned about the pressure build up do to temperature etc and would have had to incorporate pressure reliefs etc which adds to the cost. I suspect at some point I will swap mine out but it is not the highest on my priority list at the moment.

Ken
 
   / Power Trac 418 Tire fell off!!! #19  
Your loader valve already has a relief for high pressure protection while is use, and the hyd system has very little pressure when engine is off.

There is just no logic for using inferior valve off the shelf, except for price.

I can almost bet that one can replace their valve at a great cost saving.

Has anyone replaced their loader valve from PT.
 
   / Power Trac 418 Tire fell off!!! #20  
JJ - It protects for high pressure on the supply side. Does it protect for high pressure after the valve?

Ken
 
 
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