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Still working on my cat 215 excavator That you have helped…

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Hello still working on my...
Hello still working on my cat 215 excavator That you have helped me with previously and the hydraulics do not work as they should. It seems the boom circuit and travel is week. I tested the main system relief pressures like the troubleshooting section says. The front pump reaches the around 4000 psi when I extend the stick but the rear pump only reaches 2500 psi when I extend the boom. Also when I remove the test plug on the pumps the rear pump does not lose that much fluid but the front pump loses way more, I do not know if this is normal or an indication of a problem with one of the pumps The manual says to check the check valves in the combiner valve if the pressures are not the same. Do you know what I should be looking for in the combiner valve. Serial number is *****
Submitted: 2 years ago.Category: Construction and Road Equipment
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Answered in 2 hours by:
7/28/2020
Mechanic: catmastertech, Technician replied 2 years ago
catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 3,998
Experience: Field service technician for CAT 19 years.
Verified

I am sorry, my experience with these machines is limited. Most of my work has been on the engines and some basic hydraulic parts replacing. (mainly leaks and broken stuff.

The combiner valve appears to be a pair of load checks. About all you can see is the seats or check valves for damage marks were fluid is bypassing.

Since pump flow is basically a right pump and a left pump, it doesn't make since for the travel to be weak. Maybe the right track is weak since the boom is slow and the pressure is low on the rear pump.

Does the pump pressure respond better when the bucket is used for testing?

Oil draining from a port doesn't say too much about the pump. I have not been told to use that as an indicator in any of my training or experience.

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Customer reply replied 2 years ago
I didn’t watch pump pressures while using the bucket as the manual only said to use stick for front pump, boom for rear, and travel for both.it may be right track, boom, rear pump issue. The boom is weak, when I grab a load that the boom will not lift the stick will have no trouble lifting it. If the combiner valve bypasses what would the outcome be? Could it be just that the rear pump is worn. Seems like turning while traveling lugs the engine down but lifting a loaded boom does not, it just stops moving around 2500psi
Mechanic: catmastertech, Technician replied 2 years ago

All of the 200 series seemed to have trouble turning or at least they sounded like they were struggling.

I don't think it has much impact on the system and the summing valve does. I am guessing it would be weak but, I would think at a stall on any circuit it will still make power. The springs are so small, all it can really do is act as a load check. If that is the case, then you would feel a delay when it tries to combine flows.

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Customer reply replied 2 years ago
Got any ideas what the problem might be? Should I pull the combiner and inspect? It says I’m manual that there is a cap for it but I can’t really tell.
Mechanic: catmastertech, Technician replied 2 years ago

It looks like the relief valves should be checked with the summing valve.

It is under the Check of Pump Control System.

This is stuff I haven't done so, I can't say how it will change the pressures. Since the relief pressure is low on the one pump, it is where I would start.

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Customer reply replied 2 years ago
Do you know if I should have pressure at the front pump, with my gauge in the front pump,when I run the boom all the way up and hold it there? Book says to run boom for rear pump to check pressure and then move gauge to front pump and run stick all the way out and hold it and the pressures should be the same. Problem is when I have gauge in front pump and run the boom I reach near 4000psi at front pump. I am not sure if I should have any pressure at front pump when running the boom.It says if pressures are not the same to check combiner check valves. I pulled the check valves and didn’t see anything wrong with them, springs are good and the same and no pitting on the valve or seats.
If there should be pressure at either location on the front or rear pump when running either the boom or stick then why would the manual say to check at both locations while moving only the boom for rear and stick for front?
Mechanic: catmastertech, Technician replied 2 years ago

I believe that is the purpose of the combiner valve. During boom up and stick out, the demands are for much higher flow for faster machine operation.

This is done by combining the flow of both pumps to increase the boom up or stick out functions.

The newer 300 series, will also combine flow for stick in.

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Mechanic: catmastertech, Technician replied 2 years ago

I don't have experience on these so I must research the manuals to find anything to help.

Do you have a Pump Selector Valve?

The pump selector valve is manually operated. When the operator needs a rate (speed) increase of boom RAISE or stick OUT or IN movement.

This will combine flow and you would see both pumps make high pressure when stalled.

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Customer reply replied 2 years ago
No pump selector valve, I wish I did. I seen this in the manual and am wondering if this machine is supposed to have one and it was removed and bypassed at some point. Doesn’t really look like it but machine is old
Mechanic: catmastertech, Technician replied 2 years ago

I just looked back through the operator's manual and it does not even show it.

Do you see pilot lines going to the crossover sections that combine from the joysticks?

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Mechanic: catmastertech, Technician replied 2 years ago

The tubes that connect the pilot pressure lines to both valves are the ones that are performing the combining function. I am assuming the spring rates on the spool centering springs are different so the increased flow will be gradually added.

The newer machine has a special pilot valve for this feature.

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Customer reply replied 2 years ago
Can you get me a parts breakdown of the main pumps and servo valve the one that I have is from the manual and is not clear.
I pulled the spools out of the servo valves for both pumps and the one on the rear pump bottoms out on a rod that is springy but the one for the front pump just bottoms out in the barrel. I want to pull the entire servo out but I am not sure what is holding it in.
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