CAT 315-07 hydraulic noise.

[Jimbob83]

Hello all.

We own a CAT 315-07 Next Gen excavator that we bought new at the end of 2022.

It currently has 1700 machine hours on the clock, has been fully serviced at the correct intervals by our local CAT agent.

At around 300hrs the machine started making a rather loud hydraulic cavitation sound, we had CAT look at the machine and they found nothing wrong with it. At that point they carried out pressure tests and oil samples, nothing of concern was noticed. Carry on to around 650hrs and the cavitation got worse, got CAT out and their mechanic said all the new 315's have loud pumps.....OK then we thought. Get to 800hrs and I've had enough, being a every diesel mechanic myself (Sumitomo, Tigercat and hauler trained) I knew this sound was wrong. I went to the machine and removed the case drain line into the top of the pump and found a lot of brass.
Machine went into CAT and pump was removed and stripped, damage to slipper pads and plate.........they could not provide me with an answer as to why this happened. Pump was replaced, system flushed, machine run up.....which I was there for. The pump was now nice and quite........fast forward to 1700 hours and a hydraulic oil and filter change in between and now the machine is making the same noise...

CAT has been out to it, oil samples and full oil clean was done. Filter replaced and cut open, no metal found.....it is 100% the same sound and the mechanic is sure there is no issue.

Are these pump loud, is this a known issue...does any one out there have any history or experience with this?

 

[Welder Dave]

Almost sounds like there's a batch of defective pumps. Something has to be wrong or defective that it's quiet when the pump is new and gets louder and louder in a relatively short time. Maybe check if Cat has a bulletin on the issue.

 

[Vetech63]

All it takes is a small amount of debris left behind and you are right back where you started. I won't even touch contamination failures anymore. The few I tried ended up biting me in the ass at some point.

 

[DEMLONE70]

serial number ?

 

[Nige]

Are you taking regular oil samples from the hydraulic system and having them analysed for Particle Count.? I have no idea how many hours the machine clocks but off the top of my head I would say monthly, maybe even more frequently if the hours are higher.

After a failure such as you are describing you really ought to be sampling. In fact if the Cat dealer had a shred of intelligence they would have suggested it to protect the integrity of their repair & system cleaning process.

 

[Jimbob83]

Almost sounds like there's a batch of defective pumps. Something has to be wrong or defective that it's quiet when the pump is new and gets louder and louder in a relatively short time. Maybe check if Cat has a bulletin on the issue.

I have spoken with CAT agent regarding this and they are certain there is no bulletin, their mechanic did mention that another CAT of the same series/ year is making a similar sound but in his words "I was there for another issue so I didn't look any further into it and the customer didn't complain about that noise"

Are you taking regular oil samples from the hydraulic system and having them analysed for Particle Count.? I have no idea how many hours the machine clocks but off the top of my head I would say monthly, maybe even more frequently if the hours are higher.

After a failure such as you are describing you really ought to be sampling. In fact if the Cat dealer had a shred of intelligence they would have suggested it to protect the integrity of their repair & system cleaning process.

It is oil sampled at every service (250hrs), the past samples have come back OK but in saying that, the samples before I found the pump was making metal were also OK.........or so CAT has told me. I have requested copies of all hydraulic oil sample results taken by them. The hydraulic oil was changed at 1000hrs at my request...200hrs after the pump was replaced.

All it takes is a small amount of debris left behind and you are right back where you started. I won't even touch contamination failures anymore. The few I tried ended up biting me in the ass at some point.

Totally agree....CAT did extend our warranty after the new pump was fitted. I was assured that the hydraulic system was cleaned out...BUT they did not strip the valve bank, rams, final drive motors etc....it was more of a flush out. From my time as a Sumitomo tech, we would have stripped and cleaned all hydraulic components....especially if the machine had only done 800hrs work.

serial number ?

eq056325?
YDE00250?

 

[Nige]

It is oil sampled at every service (250hrs), the past samples have come back OK but in saying that, the samples before I found the pump was making metal were also OK.........or so CAT has told me. I have requested copies of all hydraulic oil sample results taken by them. The hydraulic oil was changed at 1000hrs at my request...200hrs after the pump was replaced.

Can you post up some results.? I am particularly interested in the Cleanliness Code/Particle Count. Often that test is not included in a "standard" hydraulic oil analysis and has to be requested. I don't know whether your dealer does that test automatically or whether their oil lab classes it as "optional at customer request".

EDIT: Here is an example of data extracted from an oil analysis report. It's only a small (but important) part of the overall results. The last line at the bottom is the key to knowing if a system is clean or not. This one went from "clean" in 2019 to "not so clean" in 22/23.

 

[LACHAU]

Hello all.

We own a CAT 315-07 Next Gen excavator that we bought new at the end of 2022.

It currently has 1700 machine hours on the clock, has been fully serviced at the correct intervals by our local CAT agent.

At around 300hrs the machine started making a rather loud hydraulic cavitation sound, we had CAT look at the machine and they found nothing wrong with it. At that point they carried out pressure tests and oil samples, nothing of concern was noticed. Carry on to around 650hrs and the cavitation got worse, got CAT out and their mechanic said all the new 315's have loud pumps.....OK then we thought. Get to 800hrs and I've had enough, being a every diesel mechanic myself (Sumitomo, Tigercat and hauler trained) I knew this sound was wrong. I went to the machine and removed the case drain line into the top of the pump and found a lot of brass.
Machine went into CAT and pump was removed and stripped, damage to slipper pads and plate.........they could not provide me with an answer as to why this happened. Pump was replaced, system flushed, machine run up.....which I was there for. The pump was now nice and quite........fast forward to 1700 hours and a hydraulic oil and filter change in between and now the machine is making the same noise...

CAT has been out to it, oil samples and full oil clean was done. Filter replaced and cut open, no metal found.....it is 100% the same sound and the mechanic is sure there is no issue.

Are these pump loud, is this a known issue...does any one out there have any history or experience with this?

You are a technician with perfect knowledge and experience.
I think your judgment is correct about cavitation. The main pump was damaged after it made such a noise apparently due to hydraulic cavitation.
Have Caterpillar technicians checked your machine's hydraulic system for leaks?
Fluid viscosity is a major contributor, too, especially when combined with the wrong hose or considering if that suction hose has a pinhole in it.

I am sending you an article by a very trustworthy author about this issue.

"Steve is Pumptec’s technical leader and primary resource in the areas of the design, development, and implementation of pumps, pump components, and systems. Steve has a Bachelor of Science in Mechanical Engineering from Michigan Tech University and joined Pumptec in 2011. He has more than 25 years of experience engineering and designing pumps and fluid power equipment. A hands-on guy, Steve is passionate about building new things and solving problems".

"Common Causes of Pump Cavitation
Various conditions can make a pump more prone to cavitation. A clogged filter or strainer, for example, can easily restrict flow and lead to pump cavitation. Similarly, a restricted or flimsy inlet hose might collapse and cause issues. Fluid viscosity is a major contributor, too, especially when combined with the wrong hose. Imagine drinking a milkshake through a thin straw: the combination of the thick viscosity, pressure, and weak structure of the straw causes it to collapse and restricts the flow. Or consider if that straw has a pinhole in it; the leak would also affect flow and pressure. Similar phenomena can occur in pump systems.

That said, the inlet supply hose can’t be too rigid either. If you use a solid metal hose or a system is plumbed with hard PVC or copper piping, it could cause water hammering. Finding the right combination of dampening with a strong yet soft inlet hose or flexible PVC is ideal. Here at Pumptec, we use pulse hoses with metal springs inside them to add strength and rigidity. They’re less likely to collapse yet still offer the right level of flexibility.

The position of the reservoir tank also makes a difference. If the tank is positioned below the pump, the pump will need to decrease pressure to draw the fluid vertically through the inlet piping. The longer the inlet hose and the farther the vertical distance between the tank and the pump, the greater the chance of creating a vacuum and cavitation.

Heated liquids are a major contributor to cavitation, too, especially as the hot fluid approaches the boiling point and creates additional vapour pressure. In this instance, the liquid needs to be fed/pushed through a pump rather than drawn/pulled through it. The easiest way to achieve this is to have the tank containing the heated fluid elevated above the pump so that it is gravity-fed into the pump system.

In all these instances, the flow is being disrupted or poorly executed, causing the discharge pressure to fall. The pump is basically being starved of fluid, resulting in cavitation".

For more details here:

What is Cavitation in Pumps? Learn the Causes and Cures

What causes cavitation in pumps and how can it be prevented? Understand the causes, cures, and considerations.

www.pumptec.com

 

[heymccall]

2 failures with brass?
Sounds like excess case drain pressure, not suction issues, to me.
If the a travel or swing motor is dumping excess into the case drain, that'll damage the pump(s), too.