Stupid stupid stupid 'governor' Bobcat 743

[Stevie Lee]

Hi everyone ,Im back again with another problem. I changed the oil in my motor to get that spring out, which I must say, I got out. I also changed the hydraulic filter. I went along to see my local garage, to see what specs, their products cross reference too.I told them that this machine uses the same oil in the motor and hydraulics. They rang the oil company and they sent through Halvoline Synthetic blend SAE 10w-40. I drained the oil from the motor, new filter, and new oil. Replaced hydraulic filter, which i filled with oil before screwing it back. Refilled hydraulic tank, until I could see it on the site glass, which was about a litre. Started up and ran motor for about 3 minutes. Worked the bucket up,down, tilt, and back several times, but the hydraulics keep groaning. I didn't work them for too long, before shutting it down. There seems to be bubbling in the tank, which can be seen through the site glass. I let it settle a while and tried again, but its the same. I got drive, but lifting seems to be a struggle. Firstly, is this oil okay, and secondly should I just keep lifting up and down til it comes right. I did'nt want to do it too much incase I did some damage. Thanks in advance Steve

 

[thetool]

Hi everyone ,Im back again with another problem. I changed the oil in my motor to get that spring out, which I must say, I got out. I also changed the hydraulic filter. I went along to see my local garage, to see what specs, their products cross reference too.I told them that this machine uses the same oil in the motor and hydraulics. They rang the oil company and they sent through Halvoline Synthetic blend SAE 10w-40. I drained the oil from the motor, new filter, and new oil. Replaced hydraulic filter, which i filled with oil before screwing it back. Refilled hydraulic tank, until I could see it on the site glass, which was about a litre. Started up and ran motor for about 3 minutes. Worked the bucket up,down, tilt, and back several times, but the hydraulics keep groaning. I didn't work them for too long, before shutting it down. There seems to be bubbling in the tank, which can be seen through the site glass. I let it settle a while and tried again, but its the same. I got drive, but lifting seems to be a struggle. Firstly, is this oil okay, and secondly should I just keep lifting up and down til it comes right. I did'nt want to do it too much incase I did some damage. Thanks in advance Steve

If it worked okay beffore you changed your filter, it's probably okay now. Changing the filter intoduces air into the system, which will work out, that's the foamy oil in the sightglass.
Run your boom up and down a few times, curl in and out a few times, and it will settle down. Do this and let it set overnight, and you'll notice the foam in the sight glass is gone, an the oil is clear.

 

[Tazza]

If it worked okay beffore you changed your filter, it's probably okay now. Changing the filter intoduces air into the system, which will work out, that's the foamy oil in the sightglass.
Run your boom up and down a few times, curl in and out a few times, and it will settle down. Do this and let it set overnight, and you'll notice the foam in the sight glass is gone, an the oil is clear.

Exactly, keep rinning it and it will get the air out.
Even though you filled the filter with oil you still will have gotten air in. It should settle down in time. It really does seem to cause problems with lift and tilt more than the drive. I have noticed this on machines i have pulled the pumps on. The drive feels and sounds totally normal but the lift and tilt take a lot longer to purge.

 

[thetool]

Exactly, keep rinning it and it will get the air out.
Even though you filled the filter with oil you still will have gotten air in. It should settle down in time. It really does seem to cause problems with lift and tilt more than the drive. I have noticed this on machines i have pulled the pumps on. The drive feels and sounds totally normal but the lift and tilt take a lot longer to purge.

Hey Tazza-
I wondered about this also some time ago. The charge pump for the hydrostats pushes any air right out in about two revolutions, I was told, and pulls unaerated oil in from the tank.
The gear pump has to contend with air from the cylinders and what's in the loop, as it dosen't pull continuously from the tank.
You probably already knew this but I've done a lot of dumb things lately and need to feel smart again.=)

 

[Tazza]

Hey Tazza-
I wondered about this also some time ago. The charge pump for the hydrostats pushes any air right out in about two revolutions, I was told, and pulls unaerated oil in from the tank.
The gear pump has to contend with air from the cylinders and what's in the loop, as it dosen't pull continuously from the tank.
You probably already knew this but I've done a lot of dumb things lately and need to feel smart again.=)

Thats a good point.
I was always told that the systems will self bleed and just to keep using it. I was told to avoid letting the oil go over the relief so don't let the rams bottom out. If you do, your cavetation can cause damage.
Cavetation will damage the system as when you compress oil with bubbles the air compresses and causes the bubble to implode causing basically a jet of high pressure oil that can pit the steel.