988B hyd problems

[gladiatore]

Hi guys im back again after a long season working in a quarry, I have a problem with hyd in a 988B, first i explain what i did to that machine, the equipment was stoped for more than 1 year, many missed parts, (brake acumulator, 2 hyd pumps, tranny pump, oil cooler and many small things) I install all the missed parts new and used but I took them from a machine that just broke engine, now the problem is this.


today when i come back from quarry, they called me and told me that boom and bucket stop working after 1 hour of work, i just told them was tha hyd oil cooler that is in radiator, but im still thinking what else can be the problem.

any suggestions?

Thanks in advance Lou

 

[Bob/Ont]

Check the pilot system first.
Later Bob

 

[gladiatore]

Where are located Bob?

Sorry I misspelled last part of my last post I told them wash the oil cooler located next to radiator

 

[kshansen]

Lets see if this comes through clear enough to read:

 

[kshansen]

Some basic information on how the system is designed to give you a starting point.

Copied from SIS:

The hydraulic system has two gear-type pumps. One is a double-section pump and the other is a single-section pump. The large capacity of the oil from the single-section pump is for the lift and tilt cylinders and for other hydraulic implement attachments. The large section of the two-section pump is for the steering system. The small section of the pump is for the pilot oil system for the implements and for the hydraulic brakes on the wheels.

Assuming this is how your loaders is configured. A quick check would be to see if you had working brakes, parking brake releases and wheel brakes apply. This would tell you that the pump that supplies the oil pressure for the pilot control system was still working.

Some more from SIS:

An accumulator charging valve divides the flow of oil, from the pump, for the brakes and for the implement pilot oil system. There is a filter for the pilot system oil from the accumulator charging valve. A pressure relief valve in the flow of oil from the accumulator charging valve keeps the pressure of the oil in the pilot system at approximately 325 psi (2250 kPa). The flow of oil from the accumulator charging valve that is not needed for the operation of the pilot control valve goes through the relief valve and through the oil cooler before the oil goes into the tank. An oil cooler bypass valve opens when the pressure of the oil through the cooler gets too high. High pressure of the oil through the cooler is caused by cold oil. Oil passages in the cooler that are not clean is another cause for high oil pressure.

The complete Serial Number might help to get more information. 50WXXXXX?

 

[gladiatore]

Ken thanks in advance, tomorrow i move to quarry so i let you know guys what happened, the only thing here is everything work, only boom and bucket not

 

[gladiatore]

should i take the 2 acumulators i have and change them?

 

[lantraxco]

Sounds more like to me you lost the implement pump? If the accumulators were shot you might see some issues but I doubt you would lose any function completely.

 

[gladiatore]

The problem here is pumps are almost new only 20 hours work in other machine that blow up engine, and after maybe 30 minutes rest machine after problem start work again fine until warm up again

 

[lantraxco]

Never assume anything, but yeah, still more likely to be the pilot system as Bob/Ont says. According to the information kshansen provided if your steering and brakes work the two section pump is pumping oil from both sections, and the pilot oil comes from the brake section. The things to check in the pilot system are the charging valve which divides the flow, *FILTER* and relief valve. Have you inspected and/or changed the pilot filter?

If you can read the page kshansen posted out of the service manual, it tells you where to connect a pressure gauge. Run it until it stops working and see if you haven't lost most or all of your pilot pressure.

 

[gladiatore]

Pilot filter? I'm still trying figure where is pilot system lol

 

[kshansen]

Pilot filter? I'm still trying figure where is pilot system lol

From memory I'll give it a bit of a try!

Standing behind cab looking toward rear of machine there are two doors. Open both and there should be two identical cartridge type filters near the center. One of them is the transmission oil filter, I believe a hose from the trans filter goes to a pump on the converter just above the drive shaft from the converter to the range transmission. The other canister filter would be for the pilot control system. I believe a hose from that filter goes right to the relief valve where you check pilot pressure, mounted on the right frame of the machine.

If you are standing behind the cab you will be standing on two doors in the floor, if you open them on the right side near the top are two identical filters / strainers. They have a hex plug in the top and six bolts in the cover. I'll try to attach a picture from the parts book of them. I would remove the covers and check the strainers in both these.



One of these is for the steering system and I believe the other is the hydraulic system and is in the lines leading to the pilot and accumulator charging valve.

As lantraxco suggests when things stop working check to see if the pilot pressure drops way down. I'm also there is a breather on the top of hydraulic tank might be a good idea to check to see this is clean and not causing a problem. Also in the top of hydraulic tank there the two hydraulic filters, checking and replacing them would not be a bad idea.

If many things have been opened and replaced on this machine hard to say what may have gotten in to some place to cause a problem.

 

[kshansen]

The problem here is pumps are almost new only 20 hours work in other machine that blow up engine, and after maybe 30 minutes rest machine after problem start work again fine until warm up again

Do I read this right? The boom and bucket stopped working after one hour working fine, then after sitting for 30 minutes cooling down started working again? Interesting!

Not sure what this means but I still would start by checking filters and pilot pressure. And just for the fun check clamps on all the suction lines to the pumps.

 

[gladiatore]

Guys I'm desperate now

 

[gladiatore]

Today I checked all filters and replace them, check pressure from pilot was OK, but even like that I replaced, change accumulator, check front valves (the ones under bucket), found small valve broke replaved , the big one under that replaced and keep doing same ****, it works 1 hour sometimes more some less stop work boom I let machine running for 5 to 10 mins in low rpm and start work again for 20 mins and keep doing that all day please helppppppppppppppppppppp

 

[gladiatore]

Ken if you mean the 2 small filters behind cab in floor I already checked, if you tell filters inside tank I don't, also many air go out from tank when I stop machine (not normal amount) I changed the cap for another old style, also I didn't saw the breather, by the way I told you guys what I did today in previous page, so you have better idea

 

[lantraxco]

Sounds like it's sucking air someplace, don't know if that's related to your problem.

 

[Bob/Ont]

Hyd are overheating. Check the brake charging valve is cutting in and out correctly. If it doesn't cut out the oil flow will go over relief and heat up.
Later Bob

 

[gladiatore]

Well Bob it brakes all the time even when boom stop working

 

[kshansen]

Two things.

When it stops working do you still have good pilot pressure?

Kind of a shot in the dark but have you looked at the main pressure regulator valve?
It is mounted one the large valve assembly above the front axle. I have circled it in the picture below.


Here's the cross section view: