Air in hydraulics?

banjodunn · Aug 12, 2013

G'day it sounds to me like you have got a bucket cyl seal leaking ( piston seal ) . If you have te loader up and cycle the rams though their stroke 3-4 times and then get off and try to move the bucket does it feel firm? If it is then if you leave it for half an hour or so and try to move it again then your seals or spool is bypassing.

Best way to check the cyl's is to rest the loader on the ground and remove the cyl hoses at the cyl and apply air press to the top side of the cyl i.e you are trying to extend the cyl and look for oil/air coming out the bottom fitting. I usually put a hose on the bottom fitting and run it into a bucket just in case the oil sprays out if it does then your seals are shot and need replacing.

Jon

AzChopp3r · Aug 12, 2013

Thanks banjo I will do this test in the next few days and let everyone know the results here. As for a sucking leak or cavitation, the problem exists only with the bucket cylinders and I am also not able to look into a separate hyd oil tank as I do not have one.

J_J · Aug 12, 2013

If you can't see in the tank for air bubbles, then remove a bucket hose and place in a bucket and look for small air bubbles.

Run the tractor for 5 min and work the bucket you do this test.

Maxwelshouse1 · Aug 12, 2013

When you check the hydraulic fluid make sure the loader frame is on the ground that all hydraulic cylinders are retracted (all hydraulic rods are in). Otherwise you could add too much oil. Once you are confident of oil levels, you can cycle the system several times, and go on from there... Mans temptation is to think the worst case scenario. But slow down, drink a cup of coffee and think "simple." Life gets too complicated anyways...Why make it more difficult! Lol! Good luck!

AzChopp3r · Aug 16, 2013

Ok today I was able to get to the tractor and do a couple tests.

Again, with the loader arms raised about 3 foot off the deck and bucket level, I can grab the cutting edge and lift while and see the bucket cyls retract about 2 in travel.

I then cycle the bucket 4 - 5 times fully.

Go back to the bucket and lift and it is solid. But I can tell it is sagging and at a rate of 1/2" cyl travel per min.

After a minute I can lift on the bucket and slop is already beginning to appear.

So I disconnect both cyls from the bucket and cycle them. I notice that the left cylinder is lagging considerably as compared to the right.

Thiese were the tests that I was able to perform today. Any suggestions?

J_J · Aug 16, 2013

Can you swap hoses on the valve from the lift cyls to the tilt cyls.

If the problem does not shift, then it is your seals on one or both cyl.

Ilikeurtractor · Aug 31, 2013

Can someone explain to me how the loader hydraulics "self-bleed" as referenced in this thread earlier? I'm installing a loader on a tractor now and this bleeding issue is puzzling me. I not at the point to operate the loader but am to the point where if I need to bleed it I should do it now before tightening up all the lines. It seems to me the air will stay in the lines from the control valves to each side of the piston in the cylinder unless the air is let out at the high points on each side of the piston while applying hydraulic fluid. Unfortantely, there are no bleeds at the high points, only at the connections (which are not at the high points). I'd feel better knowing how this self-bleeding works once past the control valve for the loader. Should I try to get as much air out as I can going to each ram on either side of the piston, or just hook everything up and not worry about it? I'd rather not have a "springy" loader when I'm done. Thanks in advance.

Sysop · Aug 31, 2013

"self-bleeding" just means there's nothing you need to do to do it except cycle the hydraulics throughout their full range of motion a few times. Once you start the tractor and the pump is flowing, it will push the fluid in and air out, you just need to cycle everything to ensure no air is stuck anywhere. Air being 'hidden' somewhere in the system could end up in the wrong place at the wrong time and cause a load to jerk or bounce and cause bad things to occur...

Ilikeurtractor · Aug 31, 2013

Thanks for the reply. I'm struggling with this scenario though (bare with me):

Say we have a vertical, double-acting cylinder and the piston is on the bottom (ram retracted) and we want to extend it and there is nothing but air between the control valve and the piston in the cylinder. When fluid is applied the air in the line will go into the cylinder under the piston, compress to some extent depending on load, and extend the ram. When we retract the ram from this position we apply fluid to the top of the piston in the cylinder and it pushes the fluid out first below the piston (since it is heavier than air) and the air remains in the line (or under the piston). I'm curious as to how the air gets out in this case. Unless the air leaks by the piston and gets into the top chamber where I can see then how it would be expelled out of the system upon cycling. Maybe that's how it works. I suppose air will leak by the piston more readily than fluid.