I have a 320bl that keeps blowing up swing motors and we are on number 5 at this time. I have just got involved on the last motor so I can only go from there. We had the motor completely rebuilt with all new parts. I had a Cat mechanic test the drive motors and the swivel and there were no issues with either. We did find the pilot pressure was set to 400lbs and we reset it to 650. In testing the case drain we found it elevating at times to 150lbs when reaching out with the dipper and main boom and uncurling the bucket all at the same time. Individually it stayed in the area of 50psi. We separated the case drain and ran it to the bottom of the tank to keep it under pressure and always wet to prevent cavitation of the cushion valves and everything worked for about 50 hours then she failed again. When she failed the first thing was she just didn't stop in swing, just continued to drift after the stick was returned to center. Then shortly after a few times of that she started making a metal on metal grinding sound. then she stated locking up in swing, then complete lockup. this all took place over 15 minutes of getting her for the work area to parking. Not sure whats causing the slippers to fall off and I'm at a point of either fixing or taking her to the auction or scrapping her. I really don't want to auction this nightmare to anyone.
Blowing up? Blowing seals, locking up, tearing up gears, blowing apart, blowing ? ? ? A SN would be required for better responses . . . .
Good day Issue sound familiar please see attached. Kind regards Uffex
Slippers come off, everything just grinds to pieces.
Do u have the test results of the Cat mechanic ?
Good day Yes thats the result of low or no replenishing pressure, try to find some picts. KR Uffex
Sounds to me somebody is not giving it a thorough cleaning after failure.
Who is rebuilding the motors. It wouldn't be HRD would it?
is replenishing pressure the same as pilot pressure?
No Jon the pilot pressure is something that replace the the old levers and rod's/ cables look on it the same as you would your brake servo on the auto. Replenishing comes from main pump's fluid returning to tank - if you imagine the fluid goes around the system and eventually goes back to the tank but if the fluid is cold it can by pass the cooler over a pressure relief valve if the fluid is hot the pressure is less and then the fluid is forced by the cooler matrix the relief valves are on the return tubes control this and the pressure we suspect from your description one of these are named open. I have searched for picts. but those we had were subject to a hard drive failure ( not to bore you with the details ). Look to the swing motor see if you can see a port marked "MU" if you connect into this line with a gauge during operation you would have pressure as specified we suspect you have zero or close too. If you are not so sure take some picts. of the swing and back to tank lines PM those to us we will make better instructions. Please excuse me if we appear to be explaining features that you know but it is not so easy to establish the knowledge of recipients so do not take any offence you can PM me for private assistance so keep smiling. Kind regards Uffex
I should mention there are a few Cat guys on this the forum may be able to pitch in with illustrations (May ask for serial numbers so be prepared) KR Uffex
I posted 3 pictures and the last one shows the hose routing. The one in blue(case drain) is what the Cat Mechanic changed from its normal location to where it goes now which is right into the tank return. He said it would be under the fluid level and under tank operating pressure of 11lbs so it should work fine. Is the case drain what you are referring to as the Replenishing?
Good day Jon Yes this line needs to have pressure when the machine works to save the motor. KR Uffex
The yellow hose marked red is that of case drain
I should add the hose marked blue is the replenishing line
I failed 2 swing motors in a row on my 322B. Destroyed the slipper shoes. The case drain filter at the tank end of the hose my arrow is pointing to was plugged solid. I believe it is a 5I-7950. The restriction failed the original motor, and, since it wasn't changed when the swing motor was renewed, it took the slippers off the next one in less than two weeks. Change yours, and cut open the old one. Also, that hose is where you check case drain pressure, which should never, IIRC, exceed 50 psi. It may actually be a lower spec than 50. If the filter is good, then pressure in the case drain circuit may be high when travelling (they share same case drain filter), due to leakage of the swivel seals. Put a gauge on that circuit and then stall the travel motors (steel pin in sprocket teeth), and see if case drain pressure rises.
I tested the swivel locking up the tracks and the pressure never rose. the only time is rises is moving the dipper out and uncurling the bucket at the same time, It does intermittently get up to 150 psi with the gauge mounted at the swing motor.
The one in blue is NOT the case drain. Case drain is 1/2" hose from swing motor to tee at swivel, then from tee at swivel to return filter. Gauge must be tee'd in, not just blocking port.
Moving the dipper and bucket should have little to zero effect on the combination drain of swing/ swivel/ travel motors. I really believe that you are testing the WRONG circuit (hose). Also, seeing as how the case drain hoses are most likely thermoplastic, you could have an internal hose failure, too.
Good day Jon If I am understanding your thread correctly the hose marked blue had its connection position changed to the tank, that is not correct to move the hose, when the machine is running the blue hose must have a minimum of 35 p.s.i and when you swing and let go of the RCV to stop the pressure must remain positive (Not zero). I suggest you check in the parts book check where that hose should connect make it good - adapt a low pressure gauge into that line and make sure you have the correct pressure. The pressure levels I give are the norm. for swing motors as I do not have Caterpillar information privilege's there are guys on the forum that can help with the exact numbers however in that absence use what I have given you. Excessive case drain pressure will only cause seal failure and be the root cause of swing motor failure. I hope the information helps you to get it sorted Kind regards Uffex
4MR-prefix is a Japanese-built machine built for the Japan-only market. A Japanese parts manual is reference XJBP7614. The equivalent of this machine is a 5BR or 6CR-prefix. Both models were built in Japan but were for sale to the World market as opposed to the Japan-only market. Parts Manual XEBP7645. I've attached the hydraulic schematic for that series of machines. Actually it suits all three S/N prefixes.
In the case of gear motors, yes. For this piston motor, excess case drain pressure can, and does, cause slipper shoe failure. Are you gonna make me dig back to find the info that led me there?
Good day Heymccall Thats new but we can all learn something new thats what the mind likes any idea as to the theory behind that statement ? Nige do you have a good illustration of how the replenishing line should connect ? Kind regards Uffex
that's where we had the gauge tee'd in, on the half inch line in my picture that a yellow line with the orange line i drew on it.
First google hit on "Caterpillar case drain restricted". I know there is more info on case drains for piston motors out there. https://www.hydraulicspneumatics.com/hydraulic-pumps-motors/catch-22-filtering-case-drain-lines
Return from swing motor goes to #5
Uffex, are these any use to you..? The probllem is that no single parts illustration shows all the hoses.
Smaller machine, same concept.
The explaination does not make a great deal of sense to me however I except your statement and lodged it in my memory and thank you for coming back. Kind regards Uffex
And to clarify why MY swing motors failed. Both saw excessive slipper shoe damage and complaint was low swing torque followed by overswing. After replacing the original and replacing the remanufactured swing motors, it was found that the case drain filter had not been changed for over 6k hours, leading to the initial failure. And, obviously the replacement motor failure. I can assure you that case drain filters never remain on my machines anywhere near that long anymore.
Good day Heymccall I make one comment excessive case drain pressure comes from a damaged motor or blocked filter, the motors shaft seal cannot take excessive pressure and will blow you can see many examples of that on the forum. Providing replenishing pressure is maintained there must be little risks to the slippers only in "very exceptional circumstances" to quote the Abstract article on the web. I am sorry not convinced by either articles it would be nice to question the authors somewhat. We all have our ideas which remain until convinced otherwise. Kind regards Uffex
Not here to argue... I only know from my experience, and from those who have helped solve the problems presented to me. The moment the failed reman swing motor hit the shop, I was told to verify case drain. They insisted that the case drain circuit was restricted. Had that machine for 17,000 more hours, and never touched the swing motor again. In 25 years, I have only encountered one (technically, two) swing motor slipper shoe failures. The three swing motor output seal failures that i have encountered were all worn/ hardened seals. There is no argument that a makeup line pressure issue "can" cause slipper shoe failure. It's just that I personally have not encountered that. Perhaps someone else has more experience? I also don't understand how bucket or dipper operation would increase case drain pressure, as the original poster has stated?
High case drain pressure from motors or swivel leads to swing motor faillure . Its proven by Cat
The original poster say dipper and bucket function make the case drain hit 150psi. Could full pump pressure, when stroked on other functions, leak enough through travel spools to pressurize the swivel, and then flow from bad swivel seals to the case drain? Could he be testing wrong?
The test was performed by a Cat mechanic. $2400.00 worth of testing to be exact. I witnessed the testing and the locations he took the tests. he tested the swivel and track motors by wedging a pin in the tracks and having me attempt to move against it. the case drain stayed at the -50lbs with the gauge tee'd into the 1/2'' line on the top of the swing motor. then he decided to let me operate the machine and that's when we discovered the pressure spiking intermittently to as high as 150 but only when reaching out to get a bucket of dirt. no other time and not all the time. I don't understand the reason for moving the makeup pressure line like he did other then he said it would isolate it from the elevated case drain so it wouldn't affect it. After reading this thread I am thinking that's not the right thing to do.
I might add this machine has 2 pumps also.
I noticed the case drain filter was replaced but also all the case drain lines look to be original and so I am wondering if perhaps a collapsed or peeling hose might be the problem by restricting the flow?
Good day guys I would like to make the point that I have worked from manufactures data and my own experience, if I come over as being confrontational may I apologise for that. I believe we can all learn from one another by understanding what has caused problems and it is to that end I contribute to the thread. A document produced by a major equipment outlet cannot be taken at face value folk can be mistaken which I include myself. When I look at the actual motor manufacturer installation data many warnings are published towards the end of the document none of which refer to high case drain other that the specification, if the machine can generate such high case drain when using the equipment suggests to me some other issue. So we are all coming from the same place I attach the information for your observations. Kind regards Uffex
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
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.
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.
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.
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.
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.
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