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320BL SWING MOTOR FAILURE

uffex

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Good day jon
I read your thread and drawn the following conclusion the excessive case drain reacts against the slippers, if the piston have less force that high pressure can lift the slippers loosing there respective location - so the fault is not that of the motor but some inherent fault with the 320 machine. When an excavator stands on top of a spoil heap lowers the boom casts the arm out and rolls the bucket the maximum flow of fluid is generated going back to tank and the highest return pressure combine this as you swing around adds up in my mind. This is the most economical way to shift dirt and must be a common phenomena for the 320, indeed that makes sense since you are not the only guy to have the hose moved suggests this is a known issue at Cat service. If moving the hose prevents those high case drain pressures I would suggest leave it be.
I find it extraordinary given those high drain pressures that seals have not blown out.
Kind regards
Uffex
 

heymccall

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Screenshot_20190820-100057_Chrome.jpg Screenshot_20190820-100118_Chrome.jpg Screenshot_20190820-084305_Drive.jpg Looking back...were the test done with a fresh swing motor, or while the swing motor was compromised?

Picture and description say makeup hose (blue) is case drain. That is makeup line, and according to uffex spec sheet, need pressurized (not straight to tank) to minimum of 70psi at full performance. Routing the makeup to tank will cause cavitation and subsequent shoe failure, too.
 

jonbates5

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View attachment 200725 View attachment 200726 View attachment 200727 Looking back...were the test done with a fresh swing motor, or while the swing motor was compromised?

Picture and description say makeup hose (blue) is case drain. That is makeup line, and according to uffex spec sheet, need pressurized (not straight to tank) to minimum of 70psi at full performance. Routing the makeup to tank will cause cavitation and subsequent shoe failure, too.

Hi, First I'd like to say thanks to all of you for responding . I have no experience at hydraulics and you have all been very educational.
The test was done with the new motor installed. The make up line is what was changed from it's original location and mounted direct to the return at the tank. The Idea of moving it came from the Hydraulic engineer at HPF Manufacturing ( www.hpf.com ) who originally put it into the top of the tank with no fluid able to return in case of suction. The Cushion vales started making noise after a few hours of operating and I called Caterpillar to have a certified mechanic come out. That mechanic said it was a great idea to move the line but that it needed to be in fluid and under pressure and that the tank vents at 11psi so as long as it was at the bottom of the tank it should function without problems. He relocated the line and the noise stopped. The machine functioned with out noise or symptoms for 43 hours then failed. I have learned that the system has never been cleaned out (cooler, lines flushed, ect.) Also with the original hydraulic lines still on the machine, it's very likely there's a blockage in a hose at some point that is causing the high case drain pressure.

The question I have is how did the two mechanics come up with moving the make up line in response to the high case drain pressure? seams separating the the case drain line from everything would be the fix and I though that's what they were doing? I'm a little confused as I thought the make up line was connected to the case drain by what they were explaining but what I read here is different.
 

heymccall

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All technicians have different levels of experience (and knowledge). None of us are here to argue with you or each other, but rather to help achieve a reliable diagnosis and repair.

As to your dealer tech, well, we all can't be experts, especially on rarely occurring failures.

I believe, especially based on my 322b experiences, and all of the documentation that Cat has provided, that you have either a case drain restriction, or too much case drain oil trying to make it's way up that hose.

The most bulletproof way to fix this ongoing problem is to separate the two case drains by running the swing 1/2" case drain to it's own filter and tank port. I say this because I believe that your case drain is being over volumed by either a bad seal in the swivel joint or a final drive with too much bypass.
And relocating the makeup line is definitely not anywhere on my radar, in this application, to remain reliable.
This goes all the was back to you stating that you saw 150+ psi somewhere upon using the crowd and bucket functions. That cannot happen to the case drain circuit. Something is wrong in where it is being tested.

Oh, and put the makeup hose back where it belongs.
 

jonbates5

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Location
Tacoma, Washington
All technicians have different levels of experience (and knowledge). None of us are here to argue with you or each other, but rather to help achieve a reliable diagnosis and repair.

As to your dealer tech, well, we all can't be experts, especially on rarely occurring failures.

I believe, especially based on my 322b experiences, and all of the documentation that Cat has provided, that you have either a case drain restriction, or too much case drain oil trying to make it's way up that hose.

The most bulletproof way to fix this ongoing problem is to separate the two case drains by running the swing 1/2" case drain to it's own filter and tank port. I say this because I believe that your case drain is being over volumed by either a bad seal in the swivel joint or a final drive with too much bypass.
And relocating the makeup line is definitely not anywhere on my radar, in this application, to remain reliable.
This goes all the was back to you stating that you saw 150+ psi somewhere upon using the crowd and bucket functions. That cannot happen to the case drain circuit. Something is wrong in where it is being tested.

Oh, and put the makeup hose back where it belongs.
I am definitely going to put the make up line back to it's original location. The test pressure was taken at the 1/2" case drain location on the swing motor. I do not understand how the case drain is being affected by the dipper boom but it is.
 

heymccall

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IMHO, the spike in the case drain is the most likely suspect. Where it's coming from, I dunno.
Like I said before, you can give the swing case drain it's own filter and return to tank, and walk away until the spike begins to damage the final drive(s) which tend to be more durable in respect to case drain issues.
 

uffex

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Good day Guys
As you may observe Im taking a healthy interest in this thread and will add after a study of the circuit diagram kindly supplied by Nige it clearly illustrates a fixed value by-pass relief valve at the case drain filter is this not working for some reason ? There seems to be some cross over in the discussion regarding the "Make up line" ( I have called replenishing line) and that of the case drain, looking at the diagram it is not so easy to see where that pressure transfer occurs. I believe we all agree the case drain should be a very low pressure hence the separate passage to tank where as that of the make up must offer positive pressure in all circumstances.
Jon a question for you when Cat made those tests for spike pressure was a analogue or digital instrument used for the pressure tests.
KR
Uffex
 

jonbates5

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Tacoma, Washington
Good day Guys
As you may observe Im taking a healthy interest in this thread and will add after a study of the circuit diagram kindly supplied by Nige it clearly illustrates a fixed value by-pass relief valve at the case drain filter is this not working for some reason ? There seems to be some cross over in the discussion regarding the "Make up line" ( I have called replenishing line) and that of the case drain, looking at the diagram it is not so easy to see where that pressure transfer occurs. I believe we all agree the case drain should be a very low pressure hence the separate passage to tank where as that of the make up must offer positive pressure in all circumstances.
Jon a question for you when Cat made those tests for spike pressure was a analogue or digital instrument used for the pressure tests.
KR
Uffex
It was an oil filled gauge. I am now wondering if the mechanics made a mistake in their effort to bypass the case drain. The first guy that did the work and came up with the idea to by pass it was fighting brain cancer at the time. I do believe he told one of his employees to reroute the case drain. I am now thinking the employee didn't know what line was the case drain and he moved the makeup line by mistake. Then the cat mechanic looked at it and he moved it again. Today I called the cat mechanic and asked the simple question. If the case drain was what we were testing to get the higher then normal pressure readings, why was the makeup line the one that got redirected to the tank and not the case drain. He was silent and made a sigh in the phone. then he replied " I don't know " , My suspicion is that the failure might be a separated hose, which should have been one of the first things checked, as well as filters and flushin gout the system.
 

heymccall

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The makeup line is connected to main valve's unused oil. That circuit has two pumps, slightly activated at idle pushing oil thru the main valve bank, past the thermostat, thru the cooler, and then the big return filter. When the pumps are up stroked, that volume of oil increases immensely and the pressure in the makeup hose goes up to the same pressure as the oil cooler inlet.
So, when swinging or using any other function, the makeup pressure will be higher. When swing is stopped and the swing motor ports are blocked, some of that oil is borrowed (to make up) to ensure no vacuum cavitation of the now try to stop swing motor.
This explains the 150+ psi witnessed on the gauge.

Simply replacing the drain hoses may not solve the motor failure issue as the case drain can be over volumed by a leaking swivel seal (travel oil pressure leaking past a faulty seal in the swivel joint) or worn travel motors (again during travel).
This excess volume of oil will really exceed the flow capacity of the case drain circuit & filter when combining travel and swing. This is why the document I posted way back gives acceptable flow volumes for the case drain circuit of each component, and specifically calls out the swivel, too.
 

uffex

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Good day Guys
First may I thank all for giving me some real useful information, taking a look at this issue in detail gives me a better knowledge and I hope I have been of some assistance. Please see the attached for your observations and comments.
Kind regards
Uffex
 

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