Foton 254: Hydraulic schematic different from actual piping.

[D0TC0M]

As some of you may know I am in the process of going through my tractor with a fine tooth comb. I am trying to learn how the hydraulic system works in order to diagnose the reason why after the oil gets warm that the relief valve in the stabilizing diverter valve start to make a loud bypassing noise so loud that I need to wear ear muffs in the cab. First off I have no external leaks and I'm using AW32 hydraulic oil for winter use.

The tractor works perfectly when first started up but after 20 minutes of blowing snow it will gradually start making the bypassing noise. When the noise is present it gets louder when increasing the engine RPM. With the engine RPMs high enough to make the bypass noise if i put the steering under load like when I turn the steering hard to the full left or right the noise stops momentarily. I can also make the noise subside if I slightly lift the 3PH lever or one of the levers on the multi-valve.

I've went through the hydraulic schematic from the service manual and found a discrepancy between the schematic and how its actually piped. I also will be installing 2 pressure gauges so I can monitor the pressure going to the steering and to the rear hydraulics and hopefully it will give me some insight on what could be the problem causing the bypassing noise. Below I've attached 2 images, one of the hydraulic schematic and the second is how it piped on my tractor.

 

[D0TC0M]

Is it normal to run the outlet of the pressure relief valve of the multi-valve stack to the pressure inlet of the 3PH? I know that in neutral position the 3PH diverter valve is routing the pressure port to the sump. I am assuming is alright to do so because the piping has not been modified and is stock.

I tried to find out the differences between the releif valve symbols. The relief valves #8 and the one near the number 5 are drawn differently as the one for the 3PH (near the number 4). Why is the latter drawn differently?

 

[D0TC0M]

Digging a little further I found the outlet of the stabilizing diverter valve on the firewall goes to the multi-valve assembly (as in the schematic above in post#1), where there is a relief valve (or pressure control valve) that is adjustable. I took the quick disconnect off and installed a TEE and 5000psi gauge in between the QD and the pipe end. What is the pressure supposed to be set at?

 

[jacques54]

Hi Dotcom,

The hydraulic pressure should not exceed 2200 Psi. In the schematic the difference betwin pressure release are:
The one close to no 4 is one with piloted pressure sensing, this one is on the right side of differential.

Then the two others near no 8 under the steering orbitrol and the one in the valve near no.5 for the rear outlet QD. These release looking similar and my guess is they are not piloted but just spring loaded and set by adding washers.

On my tractor the Fel was connected with QD betwin the steering priority valve and the rear remote valves. The problem was, when I dump the bucket and I want to curl further, it stop then resume curling as priority valve let build pressure.
So I routed the line different. Now it is, pump to FEL valve then the steering priority then the rear remote valve.

Jacques