my volvo 48 squeaks and it feels like the swing brake is not releasing when I turn the turntable. When I apply the thumb pleasure just slightly it feels like the brake then releases. Any thoughts on why the swing pressure is not releasing the turn table and it only releases when I hit the thumb button?
Is the thumb install new? It sounds like the DO3 has an open centre spool, not closed centre
no, the thumb has always been on it. Could it be the relay or a solenoid not activating or releasing the brake?
Could be either an electrical fault or hydraulic. Looks like your going to need to get out some gauges and your multimeter. Id probably start by checking pilot pressure going into the pilot manifold and then between the pilot manifold and the swing brake. Id check it at both high and low idle, with the pilot lever up and down, with the swing brake applied and released and when youre using the thumb and not. Im not familiar with that particular machine but usually the swing brake is released as soon as swing or any dig function is activated, and is on a delay of about 5 seconds so doesnt reapply right away when you let go of the controls. Swing brake release pressure at the motor should be pretty close to full pilot pressure. Again, im not familiar with that machine but pilot pressure is usually 500-600psi. I would check everything with run t's so everything on the machine is still hooked up and fully functioning while your gauges are plumbed in. If your pilot pressure is good but your release pressure isnt then its time to get out your multimeter. If your pilot pressure is good and your release pressure is also correct then you'll need to sit back and think about your next step before tearing things apart
Thank you, here is what I was able to trouble shoot today. I did not have the gauges but checked the voltage to the solenoid on the swing brake valve. The only time that the solenoid gets 14v is when the hydraulic line that supplies the thumb/boom turn. No other hydraulic functions active the solenoid to release the brake. I tried everything, the turntable, boom up, boom down and even curling the bucket and nothing will release the swing brake until you hit the thumb. Once the thumb is activated it stays released for around 5 seconds and locks again. I also checked the swing brake pressure sensor and its getting the 5volts that is required and its stamped, 5v on the sensor. Any thoughts on why only one of the hydraulic lines will release the brake. I also changed out the relay for the swing brake on the fuse panel but again, no change. My gut tells me its something simple and have read others asking the same questions but have not found the solution. Any advise is greatly appreciated, I guess putting the gauges back on but not sure what to test first given the swing brake is activated by voltage releasing the solenoid.
Good deal, i think youve narrowed it down. There must be a swing and dig pressure switch somewhere thats failed or had the wires knocked off it. Can you call the dealer in the morning and see if they can send you a parts pic showing its location? That way you dont spend all day looking for it and you can confirm if its the culprit or not. I dont think you need and gauges plumbed in at this point
I think uffex has a pile of info on the volvo's. If you post a serial number he may be able to help you with a location as well
The first thing I would check is the swing pressure switch. The servo lines to the swing spool should tee off and go to a shuttle block withe a switch installed. Make sure you have power to the switch on one leg and that it has continuity when activating the swing function. You could temporarily install a jumper to test whether the circuit is OK but you will not have a swing break.
Thanks - the s# is VCECR48CA00004968 for uffex and if anyone has a parts/service manual that may show the hydraulics and part numbers. My gut says that the swing brake started doing this a week or so after I pressure washed and cleaned it but I am not sure that its connected to the wash. I disconnected the swing brake solenoid and the brake stays locked and the only time it releases and gets 14v is when the thumb is activated. Boom up, boom down nor swinging left or right will activate any voltage to the swing brake solenoid that has three pressure lines connected to it through an aluminum block. One of the lines has a P and the other one goes to the turntable motor and not sure where the other one comes from. I removed the swing brake pressure sensor small sensor on back of gray vertical bar and its getting 5v (picture shown removed). I was thinking if it was the main pressure sensor or the solenoid then it would not work with the thumb activation. After the thumb activates and releases the swing brake it works great but then it relocks after, like 5 seconds. I have uploaded of the pressure gauge that is mounted on the vertical bar, a back view and right and left view of the rear of the machine. My understanding is that the swing brake solenoid is behind the vertical bar but can not been seen very well in these photos. I removed the solenoid to see if one of the lines could be blocked with trash but nothing was seen and I reinstalled with no change.
Did you try to jumper the wires at the pressure sensor? This should cause the brake to release. The thumb should not have anything to do with the swing brake as afar as I know. Does the brake release when you use the boom swing as well?
Thanks Ben, sorry about that, yes it also works and releasing the brake when I use the boom swing. Both my thumb and boom swing are on the same control. When either is pressed the brake is released for 5 seconds. Just wondering about the pressure gauge, would jumping the gauge not plow a fuse given the black wire is the ground and the green wire has the 5volts on it? Just wondering but I don't fully understand how that switch works with only 5v.
The 5v feed is a protected circuit. The only fuse is the one that feeds the ignition and VECU circuit.
okay, so it will not hurt anything to jump over on this pressure switch.
Maybe it's time you called your dealer
it looks like others are having this same issue.
Ben, I jumped the wires with a pig tail on the pressure switch and the swing brake works great!!! I'll order a new pressure sensor to solve the problem, you where right again, thank you so much for you help!