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Dan, Technician
Category: Construction and Road Equipment
Satisfied Customers: 4291
Experience:  17+ yrs. shop and field experience with all major brands of heavy equipment and trucks - 1995 WyoTech graduate.
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I have problem with my Terex TC25. Its hard to digg with due

Customer Question

Hey, I have problem with my Terex TC25.
Its hard to digg with due to it shakes, like Its to high pressure on the hydraulic system.
Submitted: 3 months ago.
Category: Construction and Road Equipment
Customer: replied 3 months ago.
The hydraulic oil and filters are new.
Expert:  Curtis B. replied 3 months ago.

Does it shake in all functions? Could the pump be sucking ir in on the suction tubes? Or filters plugged, aerating the oil? Do you see any foaming in the hydraulic tank?

Customer: replied 3 months ago.
The most shaking is in the boom cylinder but the problem is worst when combining operations, like turn the machine at the same time I swing the boom in the direction of the cabin.
There is no problem with the blade or tracks.
The oil and filters are new.
Do you know if the stand bye pressure on pump variates with rpm on the motor?
Expert:  Curtis B. replied 3 months ago.

Pressure will always vary from low rpm to maximum. If no aeration of the oil, it is possible that the boom cylinder is binding and is the cause of the jerking.

Customer: replied 3 months ago.
The mecanic I have talked to home in Sweden says that the stand bye pressure the pump is giving is to high and thats why i shakes, but they don`t know what causes the high pressure. Do you know that the correct pressure is supose to be on a TC25 ?
Expert:  Curtis B. replied 3 months ago.

No I don't, but stand bye pressure should not affect the dig function, That would be main pressure. Standbye is just the pressure to work the main pump stroke.

Customer: replied 3 months ago.
But but its only one hydraulic pump on TC25
Expert:  Curtis B. replied 3 months ago.

yes, but the standbye pressure works the control valve. Then the main pressure becomes factor, not standbye. I will opt out, maybe Dan is around and can help. He is more familiar with this than I am. Sorry. Please do not respond to me or it will lock the question to me.

Expert:  Dan replied 3 months ago.

Hi Jorgen, My name is***** will b e glad to try to help but first what is your complete model and serial number? Just to be sure I look up the correct information. TC25, TC25D, etc?

Customer: replied 3 months ago.
Hello Dan.
Its a Terex TC25 with stelnr TC00250188
Expert:  Dan replied 3 months ago.

Thanks for the updated information. This is a load sensing variable displacement hydraulic system as I am sure you are already aware so the pump output is always changing based on signal pressure in relation to the demand. If you are getting shaking it is possible due to a return restriction and possibly a pump internal problem. Open up the old filters to inspect internally for any signs of fine metallic glitter in the oil or inside the filter media indicating a pump failure occurring. Click on this link as I found a PDF service book that has all your specs, schematics, and test information for under 10.00 for the proper test procedures on your machine. Once you have downloaded the manual and run through the tests, Let me know the results or if you have found metal in the system.

Troubleshooting Manual

Customer: replied 2 months ago.
Hello Dan.
Sorry for delayed answer, was on jobsite digging yesterday.
The oil and filter was replaced for 50 hours ago when I bought the machine.
I will order new filter and check the old one for metal glitter. I will let you know when I have checked.
I have already the manual, sofar I have messured servo pressure to 32 bar. What I can see on the manual the Servopressure is supose to be 30 bar. I messured att the accumutalor tack, I´m not sure if thats the correct place to messure?
Can you tell me more about "return restriction" What can cause this?RegardsJörgen
Expert:  Dan replied 2 months ago.

Hi Jorgen, I understand as it is the busy season for me as well and I have been out on the road all this week. Sorry for the delay as well. All components send return oil back to the tank. Follow the schematics and identify the return line back to the hydraulic tank and check it for any restrictions and confirm oil is not getting restricted flow back to the tank causing higher pressure. A cause could be a component failure putting metal in the system, a foreign object left in the system from prior work, etc. If you have the manual in PDF you can gladly share with me and I can look over the diagrams and specs if you need more help . Yo can use a file sharing site and post the link or try to upload using the paperclip icon above. Let me know

Customer: replied 2 months ago.
I`m not sure I can attach the manual, its like 2000 pages :)
I`ll will wait for the new filter to arrive and check the old one for metal glitter.
What I´ve been told the stand bye pressure should be 24 bar. I have messured it to 30 bar at low rpm and 38 bar
at max rpm. could that be an issue?Also the pilot pressure is messured to 32 bar and should be 30 bar according to manual.RegardsJörgen
Expert:  Dan replied 2 months ago.

Thanks for the update. 2 bar is not much variance and will not create an issue. Let me know what you find in the old filter once opened up for sampling.

Customer: replied 2 months ago.
I will.
What about the standbye pressure?
Its supose to be 24 bar but is 38 at full trottle.RegardsJörgen
Expert:  Dan replied 2 months ago.

Try backing off the pressure with adjusting the relief settings on the relief valves.

Customer: replied 2 months ago.
I`m not sure what "Try backing off the pressure" meen? I`m not able to adjust pressure my self so need externial help.RegardsJörgen

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