Weird Hydraulic Issue cat 315CL

[TVA]

Now we are getting some results that can be interpreted. Part of what is happening is that you have combined flows from both pumps depending on situations. Run the test again this time using only the tracks. Pick up one track and slowly start it spinning. The associated gauge should slowly drop as you add speed. When it is full speed the gauge for that pump should read zero or near it. Then do the same test on the other track.

Yeah I saw that both pumps spooked up on boom up and stick operations, but I’m not familiar with CAts I’s and II’s!

 

[TVA]

if some are thinking it is a case drain (or return line back pressure issue), it could be a failed hydraulic line on the inside of the hose, making a restriction. (I am new to excavators, but have worked on farm machinery with hydraulics for a long time, and have had failed hoses on the insides more than once.). Just an outside the box thing I thought i’d offer....

I was thinking about return restriction too , but let’s just be methodical, one step at the time! This way will be clearer what’s going on.

 

[floridamechanic]

ok, swing over an lift either track and engauge both sides drop to zero on each pump, crazy part is now at idle it with boom forward it shoots unit in air better than ever has and has way more tracking response power at idle than it ever has, kinda cramped quarters for night time travel sure neighbors will have questions

 

[TVA]

Too high of a NC pressure can cause a lot of bypassing in regulators and overheat the oil! Possible reason for dropping from 2000 to 900. There’s also return filter bypass to consider.

 

[TVA]

ok, swing over an lift either track and engauge both sides drop to zero on each pump, crazy part is now at idle it with boom forward it shoots unit in air better than ever has and has way more tracking response power at idle than it ever has, kinda cramped quarters for night time travel sure neighbors will have questions

Can you see your oil temperature?

 

[floridamechanic]

yes not hot at all, can run a/c and dig hard and will stay normal, i keep all coolers/radiators pressure washed

 

[TVA]

Air

yes not hot at all, can run a/c and dig hard and will stay normal, i keep all coolers/radiators pressure washed

Is your boom down drops NC to zero now?

 

[TVA]

Air purge? Maybe?

 

[Mobiltech]

both normal digging and high idle, just did that and
boom full up both go to zero try kill engine lol

If engine is lugging too much you should also do a prv calibration (power shift pressure)The prv solenoid comes with the pump and should be recalibrated after pump change. You can do it through monitor in service mode. Password is usually f f f 2 to enter service mode.

 

[TVA]

I have to go! I would suggest leaving gauges in place and record pressures on cold oil tomorrow morning! Good night!

 

[floridamechanic]

took prv out of my pump and put in this pump, do have cat ET but prolly not smart enough to do calibrate without coach, night TVA, dozer till afternoon tomorrow-- thanks mobiltech

 

[floridamechanic]

yea gotta go for tonight, 4am comes early will get in tomorrow afternoon and see what it does cold then hot, thanks to everyone

 

[floridamechanic]

will walk machine and warm unit up and post results late this afternoon, may give more clues

 

[TVA]

Good luck!

 

[Nige]

Can't remember if I posted this before (I don't think so but I have slept numerous times since this thread started) but here is the Hydraulic Schematic.

 

[TVA]

Wow!!! There’s a world of difference!
This time it is even in colors!!!
Thanks Nige, I’m not familiar with CATs I’s and II’s, this will help!

 

[funwithfuel]

During a BOOM LOWER operation, the oil delivery from only right pump (23) is supplied to boom
cylinders (1) through boom I control valve (9). Boom I control valve (7) operates alone. Boom II control
valve (18) has a regeneration circuit that functions during the BOOM LOWER operation. This function
supplies return oil from the head end of boom cylinders (1) to the rod end of the boom cylinders.
When the joystick for the boom is moved to the BOOM LOWER position, pilot oil from pilot control
valve (20) flows through pilot line (22). The pilot oil flow then divides into three flow paths. Part of the
pilot oil flows through port (5) to boom I control valve (9). Part of the pilot oil flows through port (21) to
boom II control valve (18). The remainder of the pilot oil flows through port (7) through boom drift
reduction valve (12) and the oil acts on spool (17) .
The pilot oil flow from port (5) shifts stem (27) in boom I control valve (9) against the force of spring
(28) and spring (30). The oil delivery from the left pump in parallel feeder passage (16) flows through
load check valve (15), passage (38) and port (6). The oil delivery from the left pump then flows through
line (2) to the rod end of boom cylinders (1)
The return oil from the head end of boom cylinders (1) flows through line (3) into boom drift reduction
valve (12). Since valve (17) is shifted by the pilot pressure from pilot line (8), passage (26) is open to
drain port (8). The oil pressure that is acting on valve (12) becomes lower than the pressure in line (3).
Valve (12) is shifted to the left and the valve allows the oil in line (3) to flow through line (11). Then, the
oil flows through passage (32) and return passage (14) to the hydraulic tank. Since the return oil is
restricted at passage (32), the movement of the boom cylinders is slowed and the boom can lower at an
appropriate speed in accordance to the flow rate of the right pump oil.
Pilot oil from pilot line (22) flows through port (20) of boom II control valve and the pilot oil forces stem
(34) against spring (29) and spring (31). Now, part of the return oil from the head end of the boom
cylinders enters boom II control valve (18) and the oil flows through passage (35) to check valve (19).
The check valve opens and the oil flows through passage (39) through port (6) to the rod end of the boom
cylinders.
When the joystick for the boom is partially moved to the BOOM LOWER position, stem (27) and stem
(34) are shifted upward slightly. Passage (37) and passage (40) are partially opened and passage (32) is
closed. Return oil in center bypass passage (10) flows through partially opened passage (37) to center
bypass passage (13). When passage (37) is opened enough, an optimum amount of oil flows through
center bypass passage (13). Now, negative flow control pressure destrokes the pump for proper cylinder
operation.
Nige posted all this, I guess none of us read that far down.
Let's focus on servo vs pump in regards to right hand pump or r/h pump. It states that servo splits into 3 places. Plus side oil transfers to negative side through boom drift reduction, if that passage hangs open , it's a path to tank.
I still believe the problem lies in the boom down circuit . If the path is open to tank, there will be no/low pressure. I believe that bringing the other function helps close the passageway. When your pump is at full stroke and you suddenly close the passage, it shocks the pump, that could also be why you can hear "shoe lift" insufficient back pressure on pressure side of pump

Whatever you do, please avoid hitting additional functions while boom down. We dont want to fail another pump.

 

[TVA]

Sorry funwithfuel! Gonna have to analyze everything you said later tonight! Just super busy today!

At least I have VERY beautiful diagram from NIge now!!!

( I must be a dork, beside being an asshole, to call diagram “beautiful”)!!!

 

[Vetech63]

Steve Ahlgren's thread was 61 pages...………….lets shoot for a new record.

 

[Vetech63]

I still believe the problem lies in the boom down circuit

Agreed……..and its been said several times.