2000 bobcat 334 operarating presure?

[buster1]

I have 2300 lbs a full throttle at hydraulic pump what should it be?

 

[SSdoxie]

Some of the pressure circuits have lower relief setting than the main relief, and there were variations of hydraulic circuits used during production of 334. Not all 334s are the same.

 

[buster1]

thanks my hydraulic are slow and are week except the travel so I checked the pressure at the pump to see what I'm working with but I don't have a service manual yet. checking out to see if any one knows correct pressure.

 

[J_J]

Do you mean psi.

My Case 1845c relief is 2300 psi.

Weak is related to psi, and speed is related to GPM's.



Hydraulic System
334
Auxiliary Std Flow 16.4 GPM
Auxiliary Pressure 2600 psi

Bobcat Historical Specifications - Bobcat Company

 

[SSdoxie]

A year 2000 era 334 will have manual (cable) control for the travel and blade valve spools. Boom, dipper, bucket, & house swing have hydraulic pilot operated valve spools. If the manual controlled functions seem fine and the pilot operated functions are slow & somewhat weak, chances are the pilot circuit pressure is low not enough pressure to fully stroke the valve spools. All functions run from same pump system so if travel speed and power is fine, pumps should be OK.

 

[buster1]

my blade barely lifts machine I was told pressure should be 4200 . I should be able to get a service manual this week.

 

[J_J]

Once again.

Hydraulic System
334
Auxiliary Std Flow 16.4 GPM
Auxiliary Pressure 2600 psi

Bobcat Historical Specifications - Bobcat Company

Adjust it to secs and you should get a little more.

As far as speed of operation, if you are putting the rated GPM, that is the best you can do.

You will gain some force by adjusting the relief to 2600 psi.

You could cheat and go higher, but that is up to you.

 

[SSdoxie]

Once again.

Hydraulic System
334
Auxiliary Std Flow 16.4 GPM
Auxiliary Pressure 2600 psi

Bobcat Historical Specifications - Bobcat Company

Adjust it to secs and you should get a little more.

As far as speed of operation, if you are putting the rated GPM, that is the best you can do.

You will gain some force by adjusting the relief to 2600 psi.

You could cheat and go higher, but that is up to you.

That is only 1 version of the 334 & is from 2003 year.
2600 PSI @ auxiliary is only 1 circuit.
Yr. 2000 (D series) has 3 pump circuit. 2 of these have main relief @ 2800 psi. include travel motors, boom, dipper, bucket, auxiliary, & boom offset. 3rd pump feeds to blade & house and supply for pilot pressure. Main relief on this is 3400 psi. Only way to test this 3400 relief is dead heading blade up, all other circuits have lower circuit reliefs.

 

[buster1]

section 1 @ 2300 psi section 2@ 2800 psi section 3@ 2500psi full throttle .

 

[melli]

SYSTEM CHECK FUNCTION TO ENGAGE CIRCUIT PRESSURIZED
TEST
PORT
TARGET
(PSI) ACCEPTABLE RANGE (PSI)
JOYSTICK PILOT PRESSURE ANY JOYSTICK FUNCTION JOYSTICK PILOT GI 435 406 - 450
PRESSURE BUILD - UP VALVE NONE - CONSOLE DOWN P3 G 600 530-670
SYSTEM BY - PASS NONE - CONSOLE UP DUMP TO TANK G 60 MAX ALLOWABLE 100
MAIN RELIEF ON MANIFOLD BLOCK SWING AND ARM P3 & P2 G 3500 3400-3550
MAIN RELIEF ON CONTROL VALVE - FRONT BOOM OFFSET P1 G 2650 2550 - 2700
MAIN RELIEF ON CONTROL VALVE - REAR ARM P3 & P2 G 2900 2800 - 2950
SWING MOTOR - CROSS PORT RELIEF SWING RIGHT P3 G 2800 2650-2950
SWING MOTOR - CROSS PORT RELIEF SWING LEFT P3 G 2800 2650-2950

Pump outlet one (Item 1) [Figure 20-50-1] & [Figure 20-
50-2] provides hydraulic fluid to the right hand travel,
boom swing and boom valve sections.
Pump outlet two (Item 2) [Figure 20-50-1] & [Figure 20-
50-2] provides hydraulic fluid flow to the left hand travel,
arm and bucket valve sections.
Pump outlet three (gear pump) (Item 3) [Figure 20-50-1]
& [Figure 20-50-2] provides hydraulic fluid flow to the
upperstructure swing, blade and boost valve sections.

 

[melli]

Should also point out that you need a hydraulic tester...one that measures pressure and flow. From my manual, it says to record full flow at operating temps (Pump flow on a new piston pump is 5.23 gpm). Then slowly reduce pressure on a section by 100psi below spec (2500psi), and record flow. If high pressure flow is less than 80% of full flow, then pump repair is needed. Repeat for other pump sections...

The pump has a torque screw on side to adjust.
To adjust the hydraulic pump torque, loosen the lock nut
and turn the adjustment screw clockwise to increase pump torque.
counterclockwise to decrease pump torque.

 

[buster1]

well I bought the service manual pdf, took out the guess work . what I found out was that the no. 1 section of the pump no matter which of the relief valve settings pertinent to section no.1 are adjusted the pressure stayed the same. the relief valves for the other two sections would adjust up. some functions combine two sections of the pump that includes section 1 could not be adjusted was about 1/2 the pressure needed. looks like a new pump is in order.

 

[SSdoxie]

One failed section in a 3 section pump is very unlikely without seeing some efficiency loss in the other pumps. Unless you do a in-line flow at pressure check coming directly out of the pump (ahead of the 1st relief valves) to verify the pump is bad, I would not order/replace the pump, yet. Remove the relief valves associated with pump section 1 and inspect for worn/blown seal and signs of leakage around the poppet to valve seat. Some of these reliefs use a brass cup style poppet the spring pushes against, these poppets can wear down and leak by with age.

If you want, list the first 4 digits of your serial number and I can be sure I'm looking at same schematic.

 

[buster1]

well I was able to flow test pump and tested 8.6 perfect @ full flow . set relief pressure 2700 psi the pump reacted with a wooosh! after that the other main relief valves started working even a little high. very good no $2000 pump replacement...but arm still seams slow but has power now and swings slow 6 rpms not 9. not sure if valve are opening all the way or oil might be bypassing or left joy stick is malfunctioning or something else. thanks for all the help!