Hitachi 75zxUR oil leaking from between pumps.

[Chantrelle]

Hello, I’ve got a Hitachi 75ZXUR excavator it has oil leaking from what I believe is between the two pumps. I’ve taken one of the pumps off multiple times now to try to address the issue this most recent attempt to fix the leak. I took the pump off, cleaned everything with fine grit. Sandpaper tried to find any warpage on the two faces. Nothing was obvious tried to find any high spots again nothing very obvious I replaced the two O-rings between the pumps, which I believe are supposed to keep the oil from leaking out.

This is the third time I’ve replaced these O-rings now I believe that the oil passing between the pumps is at a low pressure and the oil is leaking out just from the pressure of gravity and the oil in the reservoir.

After putting the pumps all back together and refilling the oil last week. I’ve already lost a few litres of oil over a week from this leak and one other leak that I’m having a hard time fixing that appears to be coming from a 2 inch rubber hose I believe is called the suction hose that goes from the bottom of the oil reservoir to the pumps, with this leak at the suction hose I’ve replaced the rubber hose and hose clamps done my best to line them up with the nipples on the pipes they connect to.

I will provide pictures as well as the tag that’s on the pump. Is there any other details I can provide that would be of help please let me know. Thank you.

 

[EDUARD DCMEC]

Hola, cuando reemplazó las juntas tóricas, ¿también reemplazó los sellos del eje en las bombas hidráulicas?

¿Ya has medido la presión de las bombas hidráulicas?
Una fuga interna provoca una contrapresión excesiva en la bomba, forzando el aceite hacia afuera y dañando los sellos.

 

[Chantrelle]

Hello. Thanks for the reply.
I trust based on your reply that you can either understand English or are translating. I don’t speak Spanish but I put your reply inti a translator. I will reply in English.

No I did not replace the shaft seals. I have owned this machine for 5 years. It’s my first hydraulic machine. So I’m still learning about working in it. I live in an isolated island without heavy machinery mechanics. So I have no choice but to try to figure it out.

I have been hesitant to dig any deeper than what I’ve done with the pump as I have been told that it can be easy to cause damages and become costly to take the pump apart without experience. That being said I have looked at the diagram of the pump and it seemed that changing the shaft seals may not be to difficult.
Is this something you could speak to?
I will provide a diagram of the punk I got from a John deer employee, perhaps you could tell me which seal you think might need replacing

I also have not checked the pressure at the pump.

My understanding was the the fluid moving between the pumps was doing so at a low pressure. But it sounds like your saying the pressure or volume of oil can increase if the shaft seals need to be replaced?

Would you be able to offer any advice on how to check the pressure at the pump?

I have a friend who I believe has a gauge for checking the oil pressure. So this is something I may be able to do.

Are you suggesting the problem could Possibly be that the oil pressure need adjusting? And if not that it could also be that the shaft seal need replacing? Or is the pressure being off a result of the bad seal?

Thank you kindly.

 

[Chantrelle]

Pump diagram

 

[Chantrelle]

Hola, cuando reemplazó las juntas tóricas, ¿también reemplazó los sellos del eje en las bombas hidráulicas?

¿Ya has medido la presión de las bombas hidráulicas?
Una fuga interna provoca una contrapresión excesiva en la bomba, forzando el aceite hacia afuera y dañando los sellos.

Hey Edward just wanted to see if you got my reply. Thanks.

 

[Vetech63]

How bad of a leak are we talking about here? Since you have orings ( I assuming you are replacing those), you can use a bit of silicone sealer around the outside edge of the pump flange. Do not put any around the orings. Shaft seal leakage may increase the pressure there also, to some degree. In your pic, the little oring looks flattened to me.

 

[Chantrelle]

Well because the rubber suction hose also seems to be leaking I’m not sure how much I’m losing from just the pump.(another issue that seems obvious and easy to fix but I replaces the hose and hose clamps and it’s still leaking. Its possibke its source is somewhere else. But hard to see much up there) But it’s enough to be a nuisance. When it’s hot weather or the machine is warmed up it leaks more. Between the two leaks I lost a couple liners over a week in mild weather.

I did replace the o rings. And I have each time. I have boughten the o rings from John deer multiple times now, And they have given me two different sizes for the big I rings which is disconcerting. I just used the one that fit best.

I attempted silicone one of the times I put it back together and it causes the leak to be even worse. But I might have just done a lousy job applying it….

I could try replacing the shaft seal but I’m looking for confirmation that it’s safe for a laymen like mySelf to venture that deep into the pump. Would you know the answer to that?

Thanks for the reply.

 

[yang naiwan]

Dear chantrelle,


Please do not disassemble the excavator’s hydraulic pump for now. First, you need to clean the excavator thoroughly—use a high-pressure washer to remove all oil stains, then use high-pressure air to dry off any remaining water. After that, start the machine again and inspect it carefully to locate the exact leakage point before proceeding with any repairs.


No offense intended, but this is the kind of issue where even a mechanic cannot give you an exact answer without proper diagnosis.

 

[Chantrelle]

No offence take yang.

I have gone through that process of cleaning off the pump in the past. The oil drips from the lowest point of the face between the two pumps. And it drips even when the machine is off. I’m aware of the vagueness of this issue.
I have had conversions with multiple mechanics who were trying to help, and suggested replacing the o rings in the photos.
That didn’t solve the problem. I have had success reaching out on this forum for help with machine issues in the past and figured it’d worth a try seeking help here again.

Cheers

 

[HarleyHappy]

You may look into dye, with a UV light.
Generally, if the oil seems to leak more as it heats up, that is not usually seals, they expand with the heat. That indicates it may be more of a fitting or hose. The orings usually make up for a .020 squish, so next time you have it apart, throw a straight edge across the best lines you have.
Many times, I and other mechanics have done this with a hydraulic leak, only to find on the 3rd time it was leaking somewhere else.
I had one pump, that someone else had taken out 3 times, it was so big, they needed a crane, on my second attempt, I was checking the flatness and found a oring plug, loose as Lucy, that was causing the problem all along.

 

[Chantrelle]

Thanks Harley happy.

Because I have replaced those o rings multiple times I’m thinking if I take it apart again I should replace the shaft seal.

Is anyone out there able to tell me if accessing the shaft seal for replacement is a simple enough procedure? My fear is that I get in there and create a bigger mess than I started with.

 

[pfpm]

Which shaft seal are you talking about? the one on the piston pump is up against the engine which if it was leaking would show up near the flywheel. Not sure whether the small gear pump has a shaft seal but either way if it does and it is leaking it would just leak into the piston pump case with no harm. The small O ring is under pressure when running and the larger one is case pressure (low). As suggested give it a good clean and dry and look and wait. Are you sure the suction flange is not leaking? Oil usually runs down hill so look carefully and follow the leak track up. Also the pic does show what looks like a flat O ring.

 

[Chantrelle]

Hello pfpm

I’m not sure if there are multiple shaft seals, I’m asking about it because a few people have mentioned that a bad shaft seal could result in increased pressure which could be causing the leak.

I’m not for certain what the suction flange is. But I think I’ve got an idea what it is.
At the bottom of the oil reservoir there’s a (roughly)2”-2.5”rubber hose which connects to an aluminum pipe of the same size, that sends oil to the two pumps. Where this aluminum piece meets the pump there are some bolts to attach it to the pumps. And there’s an o ring between the face of the pump and the aluminum piece where they connect…. Is the aluminum piece that connected to the pump the what your referring to as the suction flange ?

As for that o ring being flat, I may have taken the picture when I took it apart the first time. So it was likely flat. But I have definitely put the John deer oem o ring into the pump multiple times now.

I’ll give it a good Cleaning and see if there any obvious spot the leak is coming from and report back.

Thanks everyone.

 

[HarleyHappy]

The 2 piece blocks connecting to the pump are referred to as a Code 61 flange, hydraulic crimp fitting.
They are usually pretty easy to connect, there will be a groove around the pipe, where an oring goes in, to seal against pump face.
You can take the pump apart, to check for abnormal wear.
Just make sure to scribe a line, through the sections, as there are usually at least a couple.
This will help orient it, for assembly.
If it is deemed to be leaking actually thorough the low pressure seals, then the pump is getting wore out inside.
Generally inside the pump you will have high pressure and low pressure seals and they will receive oil to help seal and cool.
Worn out pumps leak internally but generally give you some kind of warning but have had them just start pouring oil out.
Don’t be afraid of the pump, they are not too complicated.

 

[Chantrelle]

if it’s a worn out pump, is there something I can do about it?

 

[Chantrelle]

Well I found the source of a leak. There’s a crack at the bottom of the oil reservoir where the outlet pipe is welded on.

any tips on fixing this. Obviously have a welder fix it would be an option. It’s a small crack though, maybe there’s an epoxy product that could patch it?

Thanks.

 

[pfpm]

Best is to pull the tank out, grind around the whole pipe and weld it up. The crack will be a lot bigger once you grind it back. You could try something like araldite but it won't last. Looks like someone has done some welding on it before.

 

[Welder Dave]

There is fuel tank repair epoxy but is it accessible so a good welder could weld it? If the reservoir is easy to remove go that route. If not you could drain the reservoir and preheat where the crack is to burn out any oil in the crack. Grind the crack to clean steel and weld it while it's hot. If you could block the machine up first so any left over oil runs away from leak area would be the best bet. That weld is an example of why Mig welding isn't always a good idea. It is known for cold lap where it looks good but has poor penetration on one side (or both) of the joint. I'd probably try welding it with 6010 or 6011 because they are best for dirty or rusty steel and have good penetration. If you get a pinhole, grind it slightly and do a second pass. If first pass does have a pinhole the heat should be enough to burn any oil residue out of the leak. Don't attempt welding if you're not very experienced. You don't want to make it worse or be following a leak forever.

 

[HarleyHappy]

Looking close up, that’s a big crack, or it will be by the time you get done.
These jobs are best left to someone that knows what they are doing.
Just for the fact that after prep and weld and refill, don’t want to be doing it twice never mind 3 times. I would also purge tank with argon before welding.
Good job, finding the leak.
Them little suckers can be anywhere.

 

[Welder Dave]

Oil is much safer around welding than gas. You could blow some CO2 from a fire extinguisher in the reservoir prior to welding. Best way to test for leaks is to put 2 or 3 PSI air pressure in the reservoir and spray the repair with soapy water. You don't want much more pressure than that. Would be a good idea to air test before you even start and then after you've ground the area. Have the reservoir vented when welding. If there's any pressure at all in the reservoir when welding it will blow out through the weld and leave pinholes.