Weird Hydraulic Issue cat 315CL

[floridamechanic]

Cat 315cl--3644 hours--serial # cjc02070-- Have had it at hydraulic shop, one cat dealership, no one has figured it out yet, I owned diesel shop for 40 plus years and have not figured it out, will pay someone to figure it out, will give as much info as I can and maybe someone has run into this before. Started with pump howl when stick out function was opened, got worse as day went on, shut down and changed all three hyd filters and cut open and all three looked good, babied thru day finished customers job, had the pro's look at it and they are baffled, here is the current condition, put bucket on ground front of machine hit stick out and no power and pump howl, pull stick in some power and less howl, all these test are performed at full throttle, engage left track forward or reverse and split second howl then normal operation both directions, open right track no howl and normal operation, swing no issue, boom up is fine, here comes the stumper, put bucket on ground in front of machine put pressure and machine will only rise about 4 inches no pump engine strain, if you open stick out function with boom down function still full open unit will leap 4 foot in air, if you pull stick back it will not effect boom function, changed alt control function valve and does same in either pattern, ---so have pump howl and weak power on stick out--- weak an light howl on stick in--weak power on boom down unless stick out function is opened then normal power--how is stick function effecting boom down pressures? I pulled on wrenches old school way, have had a lot of ''could be'' change this change that etc, do not want to throw parts at it, have had cycle times checked, pump pressure is normal, tracks straight in line, main relief valve rebuilt, but no one can tell me the problem,I do have cat ET and no codes showing , any and all help would be appreciated and gladly paid for, 67 year old mechanic could use some help

 

[Vetech63]

Well, this is a bit confusing! LOL I have a couple of questions...………...what is the hydraulic temp running? Have you taken the lines off the stick cylinder itself and run a pressure test in both directions by plugging the lines? When the pump starts this howling is there any other effects on the hydraulic system? Have the tubelines been checked to make sure one isn't crushed or bent restricting flow? It sounds as though the problem is in the stick circuit, but when engaging other hydraulic to trouble shoot it, it becomes confusing because of the way the machine acts. I would personally eliminate the stick circuit completely. Someone else will come along with other ideas Im sure.

 

[floridamechanic]

Excellent response!!!! I clear land and bucket/rake spends it's time in the trees, i will go check hard lines, never gets over halfway up on hyd oil temp except in summer with air on, I watch it close, turn air off and slow up when starts to climb, will get fittins to put gauges on hyd lines and plug, your saying pressure test each one for matching pressures correct? Again good idea, old is only excuse I have lol

 

[Delmer]

This is over my level, I only understand simple hydraulics, and simple manufacturers. If I was tackling this, I'd buy the manual first thing, then study how the system works. Best few hundred dollars and a day's time you'll spend. Then you'll have a logical place to start looking.

My guess is you'll find something simple in the pump/valve control area, since the functions will work if you scratch your head right.

 

[floridamechanic]

More info after testing, took cap off hyd tank and pressure tested, will only hold 2 lbs, put new 10lb cap on and ran machine, hyd power a lot better than before but still some howl, now wondering if pressure pump for tank is weak, there seems to be 2 issues, may be cavitation from lack of tank pressure to feed pumps, second is the cross flow of functions, did not try before but with bucket down in front of machine and push boom down to full open will raise machine 4 inches and if you hit curl it shoots unit in air , so stick out and curl send pressure to boom down, have run into resolvers doing this on backhoe you open one function and no pump spool then bump another function you get full pump spool, guys at cat said this system is negative flow and is different, thanks Mr Delmer for responding

 

[funwithfuel]

First, do you have a pattern change valve. Some excavators have them. If you do, make sure your lever is all the way one side or the other. I had one in the past with similar issues.
What pattern are you using JD or ISO? In other words, are swing and arm on the same stick, while boom n bucket on the right? If so , if you dig teeth in the dirt, and attempt to swing, will it howl as well?
When you curl your bucket, you're stroking the other pump up and through the miracle of the center passage (not the turning joint) get the oil to your arm.
I suspect that your one pump has a weak controller. In the past , I have swapped controllers. It's not something to jump into lightly, lots of bejeezus parts to jump out if you're careless.
Since you track straight, pump is likely not hurt badly. Most importantly, does your swing act as your arm function.

 

[funwithfuel]

A little more to look at

 

[Nige]

What about the state of the suction hose from the tank to the pump inlet side..?

 

[funwithfuel]

Isn't that a common feed to both pumps? I thought the same, but then I thought they were common? I'm not sure, not my primary product.

 

[Nige]

Me neither, but any time a pump's screaming the first place I think to tick off the diagnositc list is the suction side.

Many years ago an old technical instructor gave the class some wise words about hydraulic system diagnostics - "Follow the oil. Where does it start its jounrey.? That's right - the tank. Well that's where you should start your diagnostic journey, from the same place as the oil. Maybe a large part of it will be a box-ticking exercise, but following the oil will get you to the root cause every time." Those words make just as much sense now as they did when I heard them for the first time.

 

[floridamechanic]

WOW, thanks everyone for the response and taking time to assist, does have pattern change, went there first, run with left stick swing stick function, right stick boom an bucket, change pattern the issue follows, hold boom down full throttle stick out and curl up both increase boom down function pressure, if I swap pump controllers [gulp] will the weak controller not cause other control issues? What you say makes sense b/c when this started [had wife [she runs excavator most time an I run dozer,] hold function and make pump howl sounded like was right pump standing facing pumps, put gauge on and left pump hit 5k, right pump started up bam dropped to 2k, pilot pressue 900

<---- mom/pop operation lol

 

[funwithfuel]

Here's what I would do before I opened a pump. Raise one side off the ground. Paint one track pad a visible color. Have your wife run the track full throttle in rabbit. You time the track, disregard first revolution when colored pad comes around start timing 3 full revolutions. Write it all down. Left track fwd, rev, in turtle and rabbit. Then do the same with the right. Your looking to see that they're dead even. It's kinda like a poor man's flow meter.

 

[John C.]

It would be unusual to have a pump problem with those amount of hours, but it can happen. I have seen the nut on cylinder rods come loose and allow oil to rush past the space between the nut and the inside of the piston and cause that kind of noise. As I recall that machine is two pump flow for all the implement functions so for everything else to work normally would indicate the problem being in the stick circuit. funwithfuel is correct in suggesting doing cycle times to try to narrow down the issue.

What has been done to actually confirm that the noise is from the pump? Does the pump vibrate at the same time as the howl occur? Has the pump suction strainer been pulled and inspected? Are there any codes showing on the monitor panel?

 

[floridamechanic]

scan with et no codes, tracked it in 150 foot pattern forward and reverse no drift either direction, cat did a clycle time test on boom functions all was good, have not pulled fluid and checked strainer, after replacing pressure cap I have more power but still have function crossover issue, old tank cap held 2 lbs put new 10lb on, standing at pump and opening function to make pump squall sounds like is right pump facing the pumps

 

[Nige]

If it’s any help I can post a full System Operation document for the Hydraulic System.
Here's the Hydraulic Schematic for now.
TBH I scanned through it and it made no mention of the tank being pressurized to aid pump suction.

 

[Nige]

Here's the System Operation for the hydraulic system.
Regarding the pressure cap on the tank, it is listed as such, but no specification regarding what pressure it's supposed to be.

 

[floridamechanic]

cat says 7-9 thank you sir

 

[floridamechanic]

bucket on ground in front of machine with light pressure down, hit stick out to make pump howl both pumps show and hold 4900 pounds, guess will drain tank and see flow to pumps restricted

 

[funwithfuel]

You see same pressure at both pumps? Yet pump(s) howling? How did the track test go? How are you seeing pressure, physical gauges, pressure transducer on display, measuring at the pump? Just trying to see what you see .
Have you the means to measure milliamps across a pwm valve?
Let's go back and revisit when you said you swapped out the hydraulic filters. One should have been a large diameter spin on. You found nothing in that one, not in the oil or the media?

 

[funwithfuel]

Reviewing the schematic Nige was good enough to upload. AA feeds your stick until the demand is great enough, BB joins in through stick2 spool. Stick2 us dictated by boom priority pressure reduction valve. I suspect that valve may have a bit of debris in its seat preventing you from getting stick 2 oil to stick spool.
Did you dig the teeth in and try to swing, was the howl there or not?