As a first step I suggest to test the pilot pressure. It is supplied by a pressure-reducing valve from the main system.
Spec is 348 +/- 7psi at pressure tap 1.
View attachment 243017
All the pump does is provide a flow of oil. The valve below is what controls the adjustment of the 348+/-7psi pressure. The combination of the spring #1 and the shims #2 & #5 in other words. I think that you are so far off specification with a measured pressure of 448psi that it is very possible that something is wrong inside the valve that adding/removing shims will not fix.
My first suggestion would be to remove the two Adapters #3 from each end of the valve, then remove the spool and the spring. Take a look inside the bore for scoring, etc. Check the spool for any type of damage or wear. Inspect the spring for damage and measure the free length. It should be 50.5mm. With 27.5 +/- 2.0kg of force applied to it the length should be 44.1mm. Note the quantity of thick (#2 - 0.9mm) and thin (#5 - 0.25mm) shims installed in the valve. There should also be a single spacer (#6 - 2.7mm thick) right next to the end of the spring. The quantities of each listed in the Parts Manual are shown below. Those numbers would be the starting point for making any adjustments.
I have tried two different gauges. One a digital other glycerin filled. Both read the same.It seems odd the pressure gauge reads exactly 100 PSI too high. I think Nige is correct to try a different gauge.
The blue stripe on the spring appears to be correct.
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If you have only used the same pressure gauge for all the measurements taken so far I would suggest that you try using a different gauge, just to see if it makes any difference.
I think it's also worth carrying out the tests in Steps 3 & 4 on Page 10 of the document I sent to you. To do this will involve some additional fittings because you have to tee into "Line A".
3. Raise the bucket in the air. Ensure that the lift pilot valve and the tilt pilot valve is in the HOLD position. Shut off the engine.
4. Lower the bucket for a short distance and make sure that the pressure reducing valve does not contain the higher pilot pressure that may be trapped. Precisely when the lever is returned to the neutral position, check the pilot system pressure at the outlet port (A) of 119-5988 Selector and Pressure Control Valve (3) . The pressure should be 1350 ± 100 kPa (195 ± 15 psi).
To check the Part Number of the valve please take a look at the body and see if there is either a P/N stamped on it or a data plate somewhere. The fact that you didn't find the 2.7mm-thick spacer is an indication that you could have the later P/N of valve despite the fact your machine falls into the "earlier valve" category.
I'd like some of the track loader experts to chime in because looking at the hydraulic schematic it appears to me that the pressure reducing valve can get back-fed from the lift/tilt pilot valves and I'm not sure what effect that could have on its operation. Hydraulic schematic attached.
A logical explanation. The implement hydraulic "dead engine lower" system works in a similar way on quite a few loaders.My mechanic says that the reason the valve can get back fed from the lift and tilt pilot valves is incase the machine breaks down with the bucket in the air, the pressure from the weight of the loader arms and bucket will pressurize the pilot so you can safely lower it down.
Can you confirm that the six letters in the area I marked below are NONKNN.? If so that would date the valve body casting to July 2000 - 3 months before your machine was built. That would make your PRV Assembly a 1U-2226, correct for the machine Serial Number and lead us back to the question "where is the 2.7mm-thick shim that should be in there.?"n the posts above i have included pictures of the part numbers.
That’s what I thought. But on the underside of that there is no adjustment Allen screw and jam nut it is only a smooth headed hex bolt. Is it non adjustable?I think I have found something.........
There is a pressure relief valve in the pilot pump. It is built into the head of the pump and the excess oil drains back to the implement hydraulic tank via the hose with the aluminium tag on it shown in Post #485.
See attachment. Unfortunately there are very few service parts for the pump and nothing for the relief valve, so if it is damaged then it's a case of a new pump. Since your machine was built a new 204-5130 pilot pump has been introduced. To install that pump will require a different connector on the tank line. See the attached service article.
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It is non-adjustable, but seeing as the O-ring Ref #1 in the illustration below is serviceable then doesn't the cap (arrowed) screw off somehow.? It's on the back side of your photos so impossible to see.That’s what I thought. But on the underside of that there is no adjustment Allen screw and jam nut it is only a smooth headed hex bolt. Is it non adjustable?
Can you get the head of the pump off (4 screws arrowed blue).? If there is anything that can be removed to get access to the relief valve it will be somewhere in the area of the red arrow.should I remove the pilot pump to get access for the relief and disassemble to see if there is something lodged in it?