Cat 315 CL pump noise/vibration

2005 Cat 315CL with 9000 hrs. Last fall this noise started. Would only do it when using multiple functions at once, like digging, or extending out to dump. Its a grinding/vibrating type of noise coming from the pump side of the machine. Well, i discovered I had metal in the system, so off to a Cat dealer it went. They put a new pump on. I've just got back to digging with the machine after the long winter up here, and wouldn't you know, that noise is still there at times. I just did an oil sample to keep an eye on my oil and i noticed it was full of air bubbles. Oil level is good. Anyone else see this before? Cat guys seem to be stumped on this. I will also add that the machine has already seemed to be back to its numbness, lacking power performance like it was pre-new pump.

The metal particles you had in your system prior to changing the pump were steel or bronze? Normally, if the previous pump contaminated the circuits after it failed, all the system should have been cleaned / decontaminated as thoroughly as possible (while IMHO it's practically impossible to clean it 100%). Do you know if they did that?

Small air bubbles in oil (almost foam-like) should indicate pump cavitation, I guess. Have a look inside the hydraulic oil tank for debris / dirt; change / clean the suction strainer inside the tank (if it has one - a machine s/n would help)... check the inside of the large suction hose from tank to pump inlet... those are the first things that spring to mind.

If the change was performed by a Cat dealer, isn't the new pump still covered by warranty?

The pump never failed. I caught it in time, but thru cat sos oil sampling the metal count got high enough for action to be taken. No brass, but mostly Iron. This noise had started 2-300 hrs before pump swap which promted me that something is wrong, hence the oil sampling.
The swap was all done by a Cat dealer. They did clean out system the best they could and since I've had the machine back I have a "cleanout" filter in the taink.
Yes, the reman pump has a year warranty. Whats the chance this reman is faulty? Or this cavitation issue is what took out the original pump, never got fixed, and now is working on taking out this reman?

The cleanout filter should be changed at least every week. It catches particles that a normal filter can't so it plugs easily. Sometimes those pumps on Cat can be hard to bleed and air in that pump oil or (capitation) will destroy that new pump. Check the tightness of the hose clamps on that big suction hose. If they are not really tight they can suck air there. I have seen them loose enough to suck air but not leak oil. Like the other guy said. "A plugged suction screen" can cause air bubbles to form. You need to stop running it until its fixed or you will ruin the pump very quickly.

From my experience, I've seen numerous Cat Reman double pumps on excavators working for thousands of hours after install. IMHO, the chance that your reman pump is faulty, is minimal. The problem should most probably be somewhere else in the system, and more likely on the inlet side of the pump. Perhaps you should ask the Cat dealer that performed the swap, if they inspected the inside of the tank / the suction screen / the suction line from tank to pump.

I'm not particularily familiar with the hydraulics of any Cat 315 generation, but after a brief look, both the return & suction filters should be located inside the hydraulic tank. My first guess would be to have a REALLY thorough look at both of them, especially the suction screen (I suspect the "cleanout" element is installed at the return port, but I also suspect that the return filter should have a bypass valve to shunt it in case it becomes excessively clogged).

Again, a machine s/n would, maybe, help...

MHDim said:

From my experience, I've seen numerous Cat Reman double pumps on excavators working for thousands of hours after install. IMHO, the chance that your reman pump is faulty, is minimal. The problem should most probably be somewhere else in the system, and more likely on the inlet side of the pump. Perhaps you should ask the Cat dealer that performed the swap, if they inspected the inside of the tank / the suction screen / the suction line from tank to pump.

I'm not particularily familiar with the hydraulics of any Cat 315 generation, but after a brief look, both the return & suction filters should be located inside the hydraulic tank. My first guess would be to have a REALLY thorough look at both of them, especially the suction screen (I suspect the "cleanout" element is installed at the return port, but I also suspect that the return filter should have a bypass valve to shunt it in case it becomes excessively clogged).

Again, a machine s/n would, maybe, help...

Click to expand...

S/N CJC02484
Thanks for insight. I know they inspected the tank at the time of the pump swap and everything looked good. They actually did not find any metal in there. The metal they did find was on the case drain from the pump.

r20d12 said:

The cleanout filter should be changed at least every week. It catches particles that a normal filter can't so it plugs easily. Sometimes those pumps on Cat can be hard to bleed and air in that pump oil or (capitation) will destroy that new pump. Check the tightness of the hose clamps on that big suction hose. If they are not really tight they can suck air there. I have seen them loose enough to suck air but not leak oil. Like the other guy said. "A plugged suction screen" can cause air bubbles to form. You need to stop running it until its fixed or you will ruin the pump very quickly.

Click to expand...

Thanks for the insight. I have just over 40 hours on the cleanout filter and was going to pull it tomorrow. Here is another thing i have noticed. I normally dig with the throttle on 8(out of 10). The other day it was getting boggy and making the cavitation type noise quite often. So i turned the throttle to 9, tried 10 and there was no difference in engine rpm from 9 to 10. but anyway, at 9, there was a big difference in performance and no more cavitation noise. I run it today for a few hours, all on 9, and there was no noise and machine run as it should.
Is there something to this?

This would not account for the on again off again vibration but there is a rubber drive coupler where the pump fits to the flywheel housing. That isn't loose there is it? When we changed the pump out on our 318BL a couple of years ago, we changed our coupler at the same time.

Well Sir if you see bubbles. That is cavitation and will cause it to make noise.
The engine not reving to 10 more than likely means the throttle motor needs to be calibrated. That isn't hard. Your Cat dealer or even someone on this forum could email the steps to you.
The faster you run that engine, the more oil that pump moves so, the more power and speed you get.
I assume you run it on 8 to save fuel? You may find, if you run the engine on 10 (once you fix the throttle) you will get more work done, faster thus, saving you fuel.
As far as the cavitation stopping at higher rpm? Generally, the faster you run the engine, the nastier the cavitation sound gets. Could the higher engine speed be drowning the pump sounds out?
Do the things I said earlier. If it doesn't stop. You may need Cat to come look at it while its still under their repair warranty. I have known Cat mechanics that did not know a piston style hydraulic pump like yours needs to have the pump case filled with oil and the air bled from the output side of the pump. Not all Cat dealers have dealer grade mechanics working for them.

r20d12, the higher engine rpm could be covering the cavitating noise, but I'm really doubting it. And I will restate this, the cavitating noise only occured when i would dig hard, using mutiple functions at once. Or extending out to dump out a full bucket. Other wise it would sound normal during other functions. If its cavitating for some reason, would it do it all the time while running or when its really calling for oil during the two movements like i described?
Do you think I would see bubbles in my site glass? It seems normal.
I will also restate, this cavitating noise was occuring about 300 hours before my pump went. So i'm leaning on that i had this problem before which may have taken out my pump. I told Cat about the noise but didn't seem to concerned.

The pump like you have is called a "variable" displacement" pump. Output is based on how much hydraulic flow you ask for with your controls in the cab. So, the more you make the pump do. The more the pistons will pump and the louder it will cavitate. You have a great point about the root cause not being repaired. just the pump that failed. I know oil is expensive but not as much as that pump. I never take the suction line off at the tank when I change a pump unless, I suspected an issue with the suction side. Its been a few years since I've changed a pump on your model hoe. If the suction hose connects to a bolt on neck under the bottom of the tank. The O ring could be bad. If it just clamps on a steel tube then the hose clamp could be loose. I would go through the whole suction side and check everything. I've seen a new Cat reman pump destroyed in 2 days because the Cat tech didn't know he needed to bleed the pump. I got to supervise him while he installed the other $18,000 pump. Track hoe problems can be very technical which is why they are my favorite thing to work on.
If the cavitation is caused by air in the suction side. Then yes. It could show air in the sight glass. If the pump wasn't bled properly. It won't put air in the tank because air trapped in the pump is causing the noise. You could go through the pump bleed procedure but you need to be very carefull to bleed all hydraulic pressure first. Or you can be severely injured by hydraulic injection. I hope this helps. Its hard to imagine what could be wrong with a machine when other people have touched it before I did.

Might be a good idea to change your pump suction hose. I call it a suction hose but piston pumps can't actually "suck" oil. Atmospheric pressure "pushes" the oil into the intake on the pump....

I just thought of something worth checking. Some older trackhoe's use an electric air pump to pressurize the hydraulic tank. If that pump stops, it can cause your issue. I Dont have access to that information though.

I had to replace the pump on my '03 315 CLC at about 6,000 hours. All oil was replaced but no "catch" filter was employed. My pump did not fail, nor make funny noises. It had a minor, intermittent oil leak on the pump itself. I was told no Cat re-man available for this machine and had to buy a brand new pump (I was also told that rebuild would cost more than new pump). New Cat pump was $7k and no funny noises. Total quote (including R&R) was $8,800. Once done they tried to get me to pay $14k. No calls to say they found something beyond original quote, no warning. After we picked it up I got a call to talk about the bill. I was at the store within 15 minutes. Three computer screens were lit up, and spread sheets were on display, in the service writer's office. All to demonstrate to me how I was getting a fantastic deal by paying $6k more than the quote! What a bunch of great guys they are over there!!
Cat pump had a little leak (just like the old one). Cat dealer came next day to verify (leak was noticed within 5 hours of use) and offered to rebuild. My pump leaks= me buying new pump; New Cat pump (their pump) leaks= rebuild....Cat is not what it once was. They try to sell you with claims of superior customer support but, in my experience, the only thing they deliver is lip service. How unfortunate. I used to bleed Cat yellow because I used to see great value in Cat (part of which was superior service). I have also had a bad service experience with a thumb repair (and ultimately replacement) since the pump experience. Ultimately it cost them, so far, my latest excavator purchase. I ended up buying a Deere 245G instead of the 323F Cat wanted me to buy. I paid more for the Deere as well! I digress....
Sounds to me like you are getting cavitation when you are asking for lots of oil. I would not be surprised if you have an issue with your rebuilt Cat pump though.

Well this noise was occuring at about the same rate its does now with the new reman, as it did with original. No doubt it makes this noise when calling for most oil, but doesn't seem to be something with the pump.
An update is that my original pump was not the culprit for the metal in the hydro oil. Come to find out it was my mulching attachment, which by the way, i had Cat eliminate that as a source by taking motor off mulcher, but i guess they didn't look close enough.

Something I suspected of originally seems more likely with that information. I wonder if you have debris in the pump control circuit and the pump may not be stroking/de-stroking correctly. I would think it possible to also have debris in one, or more, of the relief valves as well. Another clue that would support that theory would be an increase in oil temp.

My oil temp has been running a bar or two higher than i always remember it running at, even during cool weather. Thanks for this insight, I will look into this. I want to add that the noise is more frequent when the oil was at max temp. Yesterday was a hot day here and when i dug, the noise was happening.

Update: So I replaced the Main relief valve and adjusted the PRV which was way off. Not sure what one helped the most, but the machine performs more like it should. I still however still get a short, vibrating type noise when i dig hard, but much better than it was.

That's interesting to hear. It sounds like the relief valves may be the issue, or at least a contributing factor. Based on what you last posted I would think it would be worthwhile to disassemble the relief valves and clean them. Adding tension to the relief stack may have helped but the debris may still be in there. This may be why you had to adjust the relief valve. If this theory is correct you may be able to eliminate all the vibration and noise once everything is all cleaned out.
Im also wondering if you are still using the "clean-out" filters and/or if you have been cutting them open to see of you are still catching debris in the system.

I do have a special "clean out" filter in the tank. I just did another oil sample and should next week the results.
When you talk of the relief valves do you mean the PRV's? Wouldn't those be new and clean with the new pump?
Yesterday i had a couple hours in which it was a bit noisy. There is no question now the "noise" comes when using multiple functions, but at same time bucket in or out. I don't think i get that noise with any other combination. For example, with a heaped bucket i can swing, boom down, and stick out to move to dump the bucket, all is fine. But as soon as I open the bucket to dump, there is the noise. And the same for digging. All the motions fine, then the last curl of the bucket, there is the noise. This is not all the time, but most prevalent in those two motions. Maybe this will help pinpoint.