320BL SWING MOTOR FAILURE

[jonbates5]

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.

 

[CatKC]

keeps blowing up swing motors

Blowing up? Blowing seals, locking up, tearing up gears, blowing apart, blowing ? ? ?

A SN would be required for better responses . . . .

 

[uffex]

Good day
Issue sound familiar please see attached.
Kind regards
Uffex

 

[jonbates5]

Slippers come off, everything just grinds to pieces.

 

[DEMLONE70]

Do u have the test results of the Cat mechanic ?

 

[uffex]

Good day
Yes thats the result of low or no replenishing pressure, try to find some picts.

KR
Uffex

 

[grandpa]

Sounds to me somebody is not giving it a thorough cleaning after failure.

 

[John C.]

Who is rebuilding the motors. It wouldn't be HRD would it?

 

[jonbates5]

Good day
Yes thats the result of low or no replenishing pressure, try to find some picts.

KR
Uffex

is replenishing pressure the same as pilot pressure?

 

[uffex]

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

 

[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

 

[jonbates5]

 

[jonbates5]

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 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?

 

[uffex]

Good day Jon
Yes this line needs to have pressure when the machine works to save the motor.
KR
Uffex

 

[uffex]

The yellow hose marked red is that of case drain

 

[uffex]

I should add the hose marked blue is the replenishing line

 

[heymccall]

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.

 

[jonbates5]

View attachment 200560 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.

 

[heymccall]

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.

 

[heymccall]

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.

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.