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I have an E70B Cat Excavator that seems to have the same…

I have an E70B...

I have an E70B Cat Excavator that seems to have the same problem as this URL that I am reading.
http://www.justanswer.com/heavy-equipment/29rzk-hydraulic-both-pumps-acts-main-relief-valve-guys.htmlWhen any front pump item is operated like right travel, boom, or bucket the pressure goes to 1500 psi then abruptly drops to zero.
The only way to get pressure back is to release the lever and then actuate again.Items on the rear pump like left travel and stick will operate but the pressure will only go to about 2500.If the rear pump is deadheaded at 2500 psi and a front pump item is operated the front pump pressure will smoothly go to 3000 psi and the rear pump pressure will drop to about 1500 psi.
If the lever for the rear pump is then released the front pump pressure goes up to about 3200 psi.
As the lever for the front pump item is released the pressure smoothly drops from 3200 psi to about 2000 psi then abruptly jumps to zero and again will not operate until the lever is released and operated again.Originally this would happen when the oil was cold in the winter and go away after the oil warmed up but it has gradually become worse so it happens all the time. The oil and all filters have been changed. Adjusting the main relief valves has no effect. The pilot pressure is stable at 500 psi. I can't tell if it is a pump problem or a control problem.

Mechanic's Assistant: What is the complete model and serial number of your machine?

E70B 7YF05794

Mechanic's Assistant: Anything else you want the equipment mechanic to know before I connect you?

I hope you received the whole explanation I sent, and that should do it.

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Answered in 20 hours by:
7/9/2017
Mechanic: Dan, Technician replied 5 years ago
Dan
Dan, Technician
Category: Construction and Road Equipment
Satisfied Customers: 15,098
Experience: 17+ yrs. shop and field experience with all major brands of heavy equipment and trucks - 1995 WyoTech graduate.
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Hi my name is***** you still need help with this?

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Customer reply replied 5 years ago
The URL http://www.justanswer.com/heavy-equipment/29rzk-hydraulic-both-pumps-acts-main-relief-valve-guys.html
did not end with a resolution. I have the same model and a similar problem and I am hoping someone has the answer.
Mechanic: Dan, Technician replied 5 years ago

thanks for the update. I will be glad to help. Remove the in tank return filter. IF it is full of fine metallic glitter and brass glitter then your pumps have failed and the system will need to be flushed completely befor running the new or rebuilt pumps. Let me know

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Customer reply replied 5 years ago
The oil and filter were changed a couple months ago. I thought I saved the old filter for examination but now it is nowhere to be found. The new filter only has a couple hours of run time so I don't think it will show much.I can't see mechanically what would happen inside the pump to give the symptoms I have, and why there is an interaction between the front and rear pump.
Mechanic: Dan, Technician replied 5 years ago

If you have a pump failure occurring you will see it in the filter even after a couple hours. It will look like glitter in the oil.

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Customer reply replied 5 years ago
Hi Dan,
I worked the machine for an hour or so putting as much load on the pump as possible. The performance improves somewhat when the oil is hot. I removed the filter cartridge and checked the bottom of the cylinder that holds the cartridge. I could rub a small amount of dirt from the bottom with my finger but no metal or magnetic material. I cut open the filter cartridge and inspected the material with a magnifying glass and aside of a few tiny black specs it looked to be in new condition. I did not see anything that looked like metal or anything magnetic.Is there any way to contact the person that wrote in with the similar problem to mine to find out if he found a solution?
Mechanic: Dan, Technician replied 5 years ago

(1) Front pump

Output ... 65.5 ± 2 liter/min(17.2 ± 0.5 U.S. gpm)

At a pressure of ... 6850 kPa (1000 psi)

With pump at ... 1800 rpm

With engine at ... 1800 rpm

Power shift pressure ... 2570 kPa (373 psi)

(2) Rear pump

Output ... 65.5 liter/min(17.2 ± 0.5 U.S. gpm)

At a pressure of ... 6850 kPa (1000 psi)

With pump at ... 1800 rpm

With engine at ... 1800 rpm

Power shift pressure ... 2570 kPa (373 psi)

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Mechanic: Dan, Technician replied 5 years ago

E70B, E110B, E120B, E200B, EL200B, E240B, EL240B, E300B, EL300B Excavators

The hydraulic pump flows found in the Service Manual are for bench tested pumps and not for pumps installed in the excavator. The chart that specifies in-machine pump flows with the power shift pressure as specified. click below for the chart.

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Mechanic: Dan, Technician replied 5 years ago

When this is happening are the engine RPMS dropping as if there is a heavy load on the engine? Also have you removed and inspected the main relief valve for damaged o rings or debris?

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Customer reply replied 5 years ago
There is never a big load or drop in RPM on the engine. When the pressure on the front pump gets to 1500 PSI it abruptly drops to zero and then there is no load on the engine. I removed and inspected the main relief valves and there was no debris or damage and I replaced the small o rings under the valve seats.
I don't have equipment to measure the oil flow and it would be difficult for me to get the machine to a dealer and I might not be able to afford their prices.
Mechanic: Dan, Technician replied 5 years ago

Tee in to the pump control signal pressure and verify the signal pressures to the pump control valves.

Spec 373 PSI

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Customer reply replied 5 years ago
Do you know of a source for the fittings I would need?
Mechanic: Dan, Technician replied 5 years ago

I gained all mine over the years and if I dont have something I go to my local hose shop or parker store and get whatever tees I need.

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Mechanic: Dan, Technician replied 5 years ago

Hi, Did you get this resolved?If so, Please take a moment to rate as that is how the site credits my time helping on the site or let me know if you need more help. 5 star is always greatly appreciated.

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Customer reply replied 5 years ago
I received the fittings to make a Tee but haven't had time to assemble them and perform the control pressure test.
Mechanic: Dan, Technician replied 5 years ago

Thanks for the update. Please remember to rate my answers as that is the only way I receive credit for my time helping you from the site. We can still follow up as needed.

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Mechanic: Dan, Technician replied 5 years ago

Hello, Any gains on this? I noticed this question is still in my open question list. Please rate to close or reply back for more help

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Customer reply replied 5 years ago
The Power Shift input on the pump has about 350 PSI with mode I selected and about 250 PSI with mode II or mode III selected.
Nothing I do with the controls affectes that pressure except when a control lever is released the pressure jumps to 500 PSI for a fraction of a second. I tapped into a pilot line between the control lever and the control valve and the pressure moves smoothly from 0 to 500 PSI proportional to the lever movement even though the main hydraulic pressure goes to 1500 PSI and then abruptly drops to almost 0 when the pilot pressure reaches about 100 PSI.Is there any way to contact the person that wrote in with the similar problem to mine to find out if he found a solution?
Customer reply replied 5 years ago
The source of the problem seems to be pointing to the pump. But I can't invision mechanically what would cause a pump to build pressure to 1500 PSI then drop to zero and stop pumping, if the pump is actually causing the problem.
Mechanic: Dan, Technician replied 5 years ago

If you have good Signal/power shift pressure to signal the pumps and low output, the problem is in the pump control valve or pump itself. These are variable displacement pumps and the signal pressure to the pump control valve controls the pump output so if you have good signal pressure, no problems with the control sticking/etc then the problem is a faulty pump.

If the pump is failing to the point of producing metal you will find metallic glitter in the in tank return filter and oil. If clean, a flow meter to verify the GPM output of the pumps will confirm the actual condition of the pumps.

Please take a moment to rate as that is how the site credits my time helping on the site or let me know if you need more help. 5 star and bonuses are always greatly appreciated.

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Mechanic: Dan, Technician replied 5 years ago

Hi, Did you get this resolved?If so, Please take a moment to rate as that is how the site credits my time helping on the site or let me know if you need more help. 5 star and bonuses are always greatly appreciated.

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Customer reply replied 5 years ago
I removed and disassembled the pump and I don't see any evidence of damage or serious wear. What are the critical things to look for? Are there measurements I can take? What is in the CAT publication "Guideline for Reusable Parts Piston Pumps and Motors"?
Mechanic: Dan, Technician replied 5 years ago

Any scoring/scuffing you can catch a fingernail on is not reusable as a general rule.

Product Support Program For Main Hydraulic Pump Control Failures On Certain E70B Excavators Caterpillar

Usage:

E70B 5TG

NOTE: The information supplied in this service letter may not be valid after the termination date of this program. Do not perform the work outlined in this Service Letter after the termination date without first contacting your Caterpillar product analyst.

NOTE: This Program can only be administered after a failure occurs. The decision whether to apply the Program is made by the dealer. When reporting the repair, use "PS0543" as Part Number, "7755" as Group Number, and "96" as Description Code.

Termination Date

May 31, 1993

Problem

Poor surface finish of the main hydraulic pump swash plate may cause the engine speed to drop or stall on certain E70B Excavators.

Affected Product
Model & Identification Number

E70B (5TG1-204

Parts Needed

2 - 7J9108 Seal

1 - 6V7658 Seal

1 - 855551 O Ring

1 - 855565 O Ring

1 - 855572 Shim

1 - 855573 Hanger (Swashplate)

1 - 855581 Piston

1 - 855582 Piston

3 - 855594 O Ring

1 - 935369 Element

1 - 951575 Seal-O-Ring

3 - 951579 O-Ring

1 - 951585 Seal-O-Ring

3 - 951592 Seal-O-Ring

1 - 951701 Seal-O-Ring

1 - 951705 Seal-O-Ring

1 - 992967 O Ring

1 - 993053 Seal

1 - 993057 Seal-O-Ring

NOTE: If equipped with a dozer, the following parts will be needed in addition to the ones listed above.

1 - 992967 Seal-O-Ring

1 - 951595 Seal-O-Ring

1 - 951698 Seal-O-Ring

Action Required

Refer to the Service Manual SENR4570 and Parts Book XEBP9966.

Remove and disassemble the main hydraulic pump as required to replace the swash plate and the related parts listed under Parts Needed.

While assembling and installing the pump, make sure the bolts are tightened to the correct torques, the clearances are correct, and the correct lubricants are used.

Service Claim Allowances

NOTE: This is a 10 hour job.

Parts Disposition

Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.

Product Support Program For Replacing The Hydraulic Pump Assemblies On Certain E70B Excavators Caterpillar

Usage:

E70B 5TG

NOTE: The information supplied in this service letter may not be valid after the termination date of this program. Do not perform the work outlined in this Service Letter after the termination date without first contacting your Caterpillar product analyst.

NOTE: This Program can only be administered after a failure occurs. The decision whether to apply the Program is made by the dealer. When reporting the repair, use "PS0611" as the Part Number and "7755" as the Group Number. Use "96" as the Warranty Claim Description Code and use "Z" as the SIMS Description Code.

Termination Date

September 30, 1994

Problem

The bore in the hydraulic pumps for the 855587 Piston may wear prematurely on certain E70B Excavators. The engine speed may drop excessively when two pump are at relief pressure.

Affected Product
Model & Identification Number

E70B, (5TG205-457, 5TG459, 5TG462, 5TG467, 5TG472-474, 5TG476, 5TG477, 5TG480, 5TG482, 5TG484)

Parts Needed

1 - 5I9125 Pump Assembly (Standard)

1 - 5I9126 Pump Assembly (Equipped With Blade)

2 - 7J9108 Seal

1 - 935369 Element

3 - 951579 O-ring

1 - 951585 Seal-o-ring

3 - 951592 Seal-o-ring

1 - 951698 O-ring

1 - 951705 Seal-o-ring

Action Required

After a pump has failed, follow the procedures in the Service Manual to replace the existing pump assemblies with the new 5I9125 Pump Assembly or 5I9126 Pump Assembly. The new pump assemblies have an improved piston to reduce piston bore wear.

Service Claim Allowances

NOTE: This is a 10-hour job.

Parts Disposition

Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.

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Customer reply replied 5 years ago
Since the hydraulic pressure goes up to 1500 psi then drops to almost zero there is never enough load to slow down the motor. The swash plate is shiny with no obvious wear. There does not seem to be any play of the pistons in the barrel. The only way I can see pressure being lost is not enough spring tension holding the barrel against the end plate where the oil flows out, but that does not seem to be a problem either. There is a small amount of wear on the end plates but I can hardly feel a ridge with my finger.
Customer reply replied 5 years ago
The only thing I can think of to do is switch the front and rear cylinder assemblies to see if the problem moves or changes. I wonder if the poorly machined swash plate in the first service bulletin could evolve into the problem I am having if it had not been corrected.
Mechanic: Dan, Technician replied 5 years ago

If the tolerances are out of spec it can definitely cause an issue and may not be seen with the naked eye.

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Mechanic: Dan, Technician replied 5 years ago

Hi, Did you get this resolved? Please take a moment to rate as that is how the site credits my time helping on the site or let me know if you need more help. 5 star and bonuses are always greatly appreciated.

Dan
Dan, Technician
Category: Construction and Road Equipment
Satisfied Customers: 15,098
Experience: 17+ yrs. shop and field experience with all major brands of heavy equipment and trucks - 1995 WyoTech graduate.
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