Cat 318BL Swing is weak

[Metalman 55]

On our 318BL excavator, everything works fine but the swing seems to be weak on it. No noises or nothing loose etc., just kind of lazy.

Ser # is 3LR00468

Anyone know what pressures should be feeding into the hyd motor? If the motor was quite badly worn would the temp on the outer housing be elevated from bypassing? I have not checked the temps but could do it.

We replaced the main hyd pump a year ago ($$$) & everything else works fine on the excavator.

We don't put a lot of hours on the unit, but would like to see if it can be improved.

 

[DEMLONE70]

Swing pressure is 4000 +-140 psi
Why did u change main hyd pump ?

 

[Metalman 55]

Swing pressure is 4000 +-140 psi
Why did u change main hyd pump ?

Major failure of the pump. Thanks for the info on pressures.

 

[DEMLONE70]

Did u clean out the system ?

 

[Metalman 55]

After the pump was replaced we ran it for a short time & then checked the large screen & replaced the hyd filter. All was clean.

The weak swing problem was occurring before the pump failure & remains unchanged.

 

[mikebramel]

How soon did it occur before the pump failure? The piston shoes probably took awhile to wear down like that.

 

[Metalman 55]

The pump failure happened all at once from a performance perspective. The weak swing has been the same since we owned the machine about 1 1/2 years before the pump failure, which was about a year ago.

We don't use the machine a lot, perhaps putting on 300 hrs since owning it.

 

[toslow]

whats your pilot pressure?

 

[Bls repair]

Did you have any hoses made for the swing circuit

 

[Metalman 55]

whats your pilot pressure?

I am not sure.........we have not got into it yet. Any idea what the pilot pressures should be?

 

[Metalman 55]

Did you have any hoses made for the swing circuit

I don't believe we changed any hoses for the swing. Are you thinking of the possibility that something came loose & plugged up inside?

 

[toslow]

I am not sure.........we have not got into it yet. Any idea what the pilot pressures should be?

i think it would be no more than 500 to 600 hundred psi max pressure. but would be best to check a manual to be sure

 

[Bls repair]

I have had made hoses that were not cleaned out well take out pumps almost instantly.

 

[Mark250]

Hi Metalman 55, i have some questions please
What do you mean by lazy? slow to take off after you move the control lever ? slow slew speed ? no power trying to spread material ?
while slewing does moving another function make any difference ?
is both left and right slew affected or just one side?
some simple checks first off
make sure the slew lever has minimal play side to side ,lift the rubber boot up and check for full lever travel and is not catching on the swivel joint under the boot. standard pilot pressure is 590 psi from the pilot pump
check pilot oil pressure going to control valve by teeing into pilot lines going into the control valve should increase as lever is moved and be some where near 500psi at full travel of the control lever
Mark

 

[joeblow]

Check the case drain. Put the case drain hose into a bucket and stall the swing .If the oil comes out like a fire hose then it is swing motor.It could be a cross over relief but it is rare to have the problems in both directions

 

[Metalman 55]

Hi Metalman 55, i have some questions please
What do you mean by lazy? slow to take off after you move the control lever ? slow slew speed ? no power trying to spread material ?
while slewing does moving another function make any difference ?
is both left and right slew affected or just one side?
some simple checks first off
make sure the slew lever has minimal play side to side ,lift the rubber boot up and check for full lever travel and is not catching on the swivel joint under the boot. standard pilot pressure is 590 psi from the pilot pump
check pilot oil pressure going to control valve by teeing into pilot lines going into the control valve should increase as lever is moved and be some where near 500psi at full travel of the control lever
Mark

We have owned this machine for about 2 1/2 years now & right from day one for us the swing has been lazy, slow to get going when you change direction & very much lacking in power, just seems weak in both directions.

Everything else on the machine works good given its age.

We have a man with more experience that us coming out on Friday to do some pressure tests for us.

Thanks for the information on the pilot pressures.

We replaced all filters again this morning, after having 180 hrs since the pump replacement a year ago.

All filters were pristine, except the large tall filter inside the filter housing has some brass slivers at the very bottom of the filter once cut apart. See pics.

 

[mikebramel]

That pump was probably wearing down for awhile. Probably sent some of it's debris into the swing motor. You probably noticed the lack of performance from the pump when the shoe lands were completely shot and the piston let loose. Before then it was sending the brass down stream for who knows how much time

 

[Metalman 55]

Ok........more to report on here.....

Both inlet lines to the swing motor read 3400 psi.

Delivery from both sections if the main pump read 5000psi. I was not aware that the pump had two halves.

Lastly, the case drain produced about 1 litre (approx. one US Quart) in about 15 seconds when the swing function was activated & there were a few tiny bits of brass in the mix. Does that quantity of oil spell trouble?

We are thinking because we found some bits in the mix, off comes the motor.................

 

[DEMLONE70]

So pressure is 600 psi to low
Flow case drain is on new motor
15 litre per minute or 4.0 US GPM

 

[John C.]

Some machines had a free swing function and others had a soft swing. Either option will do what you are describing. The case drains sound high to me also.

Pulling the motor is not a big deal and they are not hard to tear down and inspect. About three hours max for your first one and being very careful.