Swing Dynamic Braking PC170lc-10

[snoyes]

Hello
PC170lc-10 excavator sn 30072
I have a swing / dynamic braking issue. Swing parking brake works as it should.
Problem is: when pilot functions are applied, bucket,boom,dipper, the parking brake releases as it should, as soon as the brake releases the machine will drift side to side depending on ground level.
Im not sure what holds the machine from turning dynamic brake wise? ie swing motor or spool valve main control
what i have done so far
-pulled spool main control valve all seems good
-adjusted compensation valves on swing motor to spec
-did leakage test on swing motor all good
-pulled two poppet valves on swing motor springs good the seats in motor head are beat up
Again I'm not sure how the dynamic brake oil is contained
thanks
scott

 

[heymccall]

Are you sure that the machine isn't in "Fine swing" mode.

 

[snoyes]

Are you sure that the machine isn't in "Fine swing" mode.

thank you
would that mode be turned on through the monitor? i'm more of a mechanic than a operator

 

[skyking1]

Not familiar with that model, but @heymccall is spot on with his guess, is my guess too.
On many machines it is a button on the console behind the right armrest. It is an option on some machines and is easy to bump. Then you are a slave to gravity.
I have used it on Cat 320 when doing crane work. Get the carriage really level and now it behaves like a crane, very smooth with no cogging action.

 

[snoyes]

Not familiar with that model, but @heymccall is spot on with his guess, is my guess too.
On many machines it is a button on the console behind the right armrest. It is an option on some machines and is easy to bump. Then you are a slave to gravity.
I have used it on Cat 320 when doing crane work. Get the carriage really level and now it behaves like a crane, very smooth with no cogging action.

just noticed its in ATT/P mode {2-way attachment} could this mode free swing the unit?

 

[Gary Layton]

My CAT 320C was doing the same thing when I bought it..used and had very little knowledge of excavators. It was that fine control switch. Here is what mine did.

 

[Marcrus]

There's no fine swing on those machines, if the brake is releasing and it's slewing I'd be first checking pilot oil pressure going to the slew spook to make sure it's not coming from the ppc leavers bypassing or misadjustment.
Then I'd be inspecting the cross port reliefs and slew holding valvings

 

[Hffhvg]

-did leakage test on swing motor all good

I would also try to check the case drain with cold oil and then with hot and compare the results. Your current test may be up to spec but deviation in cold vs hot oil would be an indication that there is oil escaping through the rotary group of slew hydraulic motor. Tolerance between the bores of the cylinder block and pistons can wear down by a few hundreds of a millimeter which is enough to cause drift on a slope. If there is deviation in hot/cold oil I would look into the hydraulic motor.
But first I would also check the swing motor relief valve pressure, them failing or not being set correctly would also cause drift on a slope.