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Weird Hydraulic Issue cat 315CL

TVA

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We may be dealing with “multiple offenders” here! OP said that he had some fluid overheating issues, couldn’t use a/c and had to slow down in summer. That could have degraded the oil, and degradation of oil led to slippers saying “ screw it, we not gonna take it anymore!”
 

John C.

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The statement that NC pressure went to zero when each track was activated tells me the system is now working correctly. Could you tell us the NC pressure with all controls at neutral. My thought is that when hooking up the gauges, perhaps a piece of debris was dislodged and fell out of the fittings.

The way the system works is that as pressure falls on those circuits the pumps stroke up. In the boom down scenario if pressure didn't fall the pump would not be fully stroked meaning there would not be enough oil to push the boom down and make up for any leakages or partially open relief valves to enable lifting of the machine. The way to check that is to observe the NC pressure while pushing down on the boom. The NC pressure should drop to near zero for the pump that supplies boom down.
 

floridamechanic

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afternoon, ok it is 80 degrees here so difference hot/cold on oil is minimal
boom up pump drops to zero quick, boom down goes from 850 to 450 but do have power to raise machine even at half throttle, tracking power is huge increase from ever before, will not track straight the right track is stronger causing drift to left, not major but noticeable[this same pump for boom down}, never been this way before, but when tracking both pumps go to zero quickly,
pump idle or high idle pressures stay same pump#1 is 650lbs pump #2 is 900lbs, funforfuel is right in single function very seldom slipper noise, multifunction get a lot more, so boom down not dropping ALL nc pressure, because set to high to handle that much pressure??? dropping 4-5 hundred pounds, which is about half of what is carrying, ya'all already know I sure do not know about his stuff but how about If I pull the nc lines and drain into clean glass jars see any debris?
 
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TVA

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If it was me next thing I would be checking boom down actuator and pilot hoses to it.
 

funwithfuel

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Remember boom down by design does not require as much effort or flow because gravity is working with it the only time pressure comes into play is when you hit ground and your trying to break Through the soil
 

floridamechanic

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boom goes down excellent an very strong compared to other day, swing over side and boom down shoots in air with authority at idle, it is slipper noise that scares the bjeeezzz outta me
 

John C.

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Draining the hoses is a good thing to do to eliminate a potential source of the problem. I would also check the fittings on both the pump and the valve to make sure they are clean also.

So the pump that handles boom down is at 900 PSI for NC pressure all valves in neutral. So which pump feeds the right side track? The one with the high NC pressure in neutral or the one with the lower NC pressure in neutral?
Pilot pressure has nothing to do with this problem.
 

TVA

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Pilot pressure moves the spool which supposed to cut the flow in central passage, just wanted to make sure that actuator is not leaking.
 

floridamechanic

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boom down and strong right track same pump= one with strong nc pressure---will pull lines and fitting and blow out and check in morning
 
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TVA

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As far as we know the only function that doesn’t drop NC pressure is boom down, and it shares drain orifice, unloader, and pump with boom up, both bucket functions and right travel.

What it doesn’t share with mentioned above?
Joystick spool, pilot hose, actuator and 1/3 of the main spool.

I’m gonna be laying down possibilities and you can add to it:

Leaking joystick spool

Restricted hose

Leaking or somehow not fully functioning actuator

Debris on the other side of the main actuator

Scratched up and leaking spool and/or bore for boom down.
 

funwithfuel

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Go back and separate joystick/servo from neg control. Have we established that the servo oil to boom A port is equal to servo at boom B port? For example if you have 550 psi pushing spool @ A side, when requested, do you see 550 at other side when opposite function is demanded?
By the same token , is the neg control drop off equal when spool is shifted from neutral to A and neutral to B? This is a lot of measuring, but I think is necessary.
 

John C.

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Let us know how things work after you clean out the lines and NC valves. The high NC pressure on pump #2 is possibly caused by misadjusted pump control. If the NC valves on the main control valve are good then the minimum flow regulator on the pump needs to be adjusted. The same may be true for the maximum flow adjustment on the same pump and be the reason the right side is a little more powerful. As I recall in this thread this is a used pump?
 

Mobiltech

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Negative flow can be adjusted on each pump. A high setting on negative flow screw in pump will affect tracking. It will also increase nfc pressure signal. You will need to adjust the pump.
 

Mobiltech

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g00764907.gif Testing and Adjusting
315C Excavator Hydraulic System


Media Number -RENR5519-08 Publication Date -01/06/2007 Date Updated -20/06/2007



i01463605
Pump Control (Negative Flow) - Adjust
SMCS - 3222-025-FW
View Image

g00764907.gif

Illustration 1 g00764907
Pump regulator (right pump)
(1) Bolt
(2) Cover
(3) Seal
(4) Spring seat
(5) Spring
(6) Shim
Perform the following steps in order to adjust the right pump.

  1. Remove two bolts (1).


  2. Remove cover (2) and seal (3).


  3. Remove spring seat (4) and spring (5).


  4. Add shims (6) in order to increase the negative flow. Remove shims (6) in order to decrease the negative flow. Refer to Table 1 for available shims and shim thickness.
    Note: A change of 0.1 mm (0.0039 inch)in shim thickness will change the negative flow rate 2 L/min (0.5 US gpm)at a negative flow control pressure of2350 kPa (340 psi).

    Table 1
    Available Shims
    Part Number
    Shim Thickness
    099-3669
    Shim 1.00 mm (0.0394 inch)
    099-6109 Shim 1.05 mm (0.0413 inch)
    099-6110 Shim 1.10 mm (0.0433 inch)
    099-6111 Shim 1.15 mm (0.0453 inch)
    099-6112 Shim 1.20 mm (0.0472 inch)
    099-6113 Shim 1.25 mm (0.0492 inch)
    099-6115 Shim 1.30 mm (0.0512 inch)
    099-6117 Shim 1.35 mm (0.0531 inch)
    099-6118 Shim 1.40 mm (0.0551 inch)
    099-6119 Shim 1.45 mm (0.0571 inch)
    099-6120 Shim 1.50 mm (0.0591 inch)
    099-6121 Shim 1.55 mm (0.0610 inch)
    099-6122 Shim 1.60 mm (0.0630 inch)
    099-6123 Shim 1.65 mm (0.0650 inch)
    099-6124 Shim 1.70 mm (0.0669 inch)
    099-6125 Shim 1.75 mm (0.0689 inch)
    099-6126 Shim 1.80 mm (0.0709 inch)
    099-6127 Shim 1.85 mm (0.0728 inch)
    099-6128 Shim 1.90 mm (0.0748 inch)
    099-3670 Shim 1.95 mm (0.0768 inch)


  5. Install shims (6) in the pump regulator.


  6. Install spring (5). Install spring seat (4).


  7. Install cover (2) and seal (3).
    Note: Inspect seal (3). If the seal is damaged, replace the damaged seal with a new seal.



  8. Install bolts (1). Tighten bolts (1) to a torque of 95 ± 15 N·m (70 ± 11 lb ft).
Adjust the left pump in the same manner as the right pump.
 

TVA

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That’s not a negative PRESSURE adjustment, that’s a minimal stand by FLOW adjustment, it’s even stated in that instruction. The negative pressure regulated by NC relief valves in control valves, and if NC pressure stays the same through all range of RPMs then those reliefs work correctly ( but miss adjusted) and there’s no restriction in the drains.
And you right about miss tracking if the NC is different between the pumps at the same RPMs than track motors will be getting different flow at the same RPMs. But this statement only true for partially open pilot valves, or if at fully open pilot valves theres still a NC pressure on one or both sides.
 
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TVA

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And we FINALLY we have the right value for NC pressure which sounds about right - 340 psi!!! That’s a far cry from 900-1000 psi.

Thanks!!! Mobiltech!
 
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floridamechanic

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ok going to clean out lines today, the nc lines go into side of block, where are the valves?? my plan was to pull lines and use siphon gun with diesel to blow out and check flow,just reread post, so if I pull control valve for boom up and boom down and their reliefs clean all them and blow out passages then test, the nc valve is in the control valve, will do this today and report back, have to put new idler on my dozer first, new ITR undercarriage and Right rear had bearing failure in 200 hrs so replaced whole idler in warranty, now at 240 hours has another, as you can see I do my best to stay away from normal stuff,
 
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