Getting tired of hydraulics- Another help needed thread

[wdchyd]

But you're missing the point....the gauge tells you if your valve is doing it's job....it gives you definite direction to your trouble.....

Most problems like you describe leads me to the cyl....bucket tilt cyls hanging on the front of a machine like that can take a lot of abuse but many get damaged internally....you wont know till you yank it and check it out.....

I've had countless guys like you come to my shop with a control valve in hand and tell me "Rebuild It"....when all it needed was a cyl repack.....this story is not something new to me or alot of others here....

 

[wdchyd]

The only way it could be the cylinder is if it were leaking externally, but its not.

Wrong....if the piston seal is blown, the cyl would NOT leak externally....Don't go by external leaks.....

 

[futuresweets10]

Wrong....if the piston seal is blown, the cyl would NOT leak externally....Don't go by external leaks.....

Yes, but if the piston seal were blown it wouldn't hold pressure one way, it would bleed down from both sides. The piston seal is what seals the two halves of the cylinder from each other. If it leaks one way it would have to leak the other way. I just dont see how it could hold pressure on one side of the seal, but not the other.

I am far from an expert on this subject, so I may be wrong. However, it goes against all laws of physics and what I know for it to be possible. If it is possible for the cylinder to leak one way but not the other please explain how, as I cant see it.

 

[AKKAMAAN]

The way cylinder is hooked up....bucket tilt drops down when cylinder extends, and bucket tilt lift when cylinder extends, If cylinder seal is blown, the oil volume on the capped side is bigger than the void space on the rod side....the volume of the rod is the difference....that volume of oil need somewhere to leak out, and the DCV is the only leak possibility if there is no external leak. If spools were leaking, it is very unlikely they would be so worned, so bucket drop that fast down.....so the leakage is probably in the work port valve.....

Here is the thing to pay attention about when this scenario occurs....
With a blown seal (or piston off the rod), the rod itself will become piston, a 2" rod will only have a 3.14 sq inch cross area, but still at 2500psi would hold 7800lbs of force....enough to hold the bucket tilt??? I would think so.....if not....the work port relief is by passing/leaking.....

 

[dcyrilc]

Morning AKKAMAAN. One thing to keep in mind, that Cat backhoe is probably a CC system. Not a big impact, but there are some differences that should be kept in mind.

 

[AKKAMAAN]

Morning AKKAMAAN. One thing to keep in mind, that Cat backhoe is probably a CC system. Not a big impact, but there are some differences that should be kept in mind.

I suppose you refere CC as Closed Center system..
Any way, CC, OC, CP, CF or LS....it do not matter at all, as long as the control valve is in neutral....these system design options, is basically only a design issue from pump to the spool....between spool and actuator all systems are designed the same....LS can be a minor exception if load signal is retrieved from the work port, and that would be through a 1/32" orifice that could not drain the cylinder in that short time anyway

 

[wdchyd]

I am far from an expert on this subject, so I may be wrong. However, it goes against all laws of physics and what I know for it to be possible. If it is possible for the cylinder to leak one way but not the other please explain how, as I cant see it.

You are "assuming" without using a pressure gauge.....trust what you see using gauges.....

Would you trust an electrician to troubleshoot who doesn't use an Amprobe/Volt Meter?....I wouldn't.....:confused2:

The piston seals on these Cats work under extreme pressures, here's what your piston seal looks like....(This pic was today repacking a Cat 416 Boom Cyl) it's the same seal kit in your tilt cyl......1.875 Rod X 3.250 Bore......

Anythings possible when it comes to hydraulics....These seals can hold in one direction only if its damaged or the bolt loosened up......

The seal being held is the 2 piece piston seal.....that seal holds up the entire bucket when its working right.....

 

[Qapla]

I am definitely NOT a hydraulics expert. But I will pose this question:

Is it possible that one of the hoses has/had a "kink" in it (especially if they have some age on them) that could cause a small rupture of the interior wall of the hose? A small tear like that on the inside could act like a "valve" by allowing fluid to pass in one direction and block the flow in the other.

This may be way off base, but I thought I'd ask. :thumbsup:

 

[AKKAMAAN]

I am definitely NOT a hydraulics expert. But I will pose this question:

Is it possible that one of the hoses has/had a "kink" in it (especially if they have some age on them) that could cause a small rupture of the interior wall of the hose? A small tear like that on the inside could act like a "valve" by allowing fluid to pass in one direction and block the flow in the other.

This may be way off base, but I thought I'd ask. :thumbsup:

It is not off base, I have had a similar thing happen to me on an old SAAB car...it was the flex hoses connecting to the front wheel disc brakes that had collapsed inside lining ....and the inside lining started working as a check valve...and brakes didn't release....stuck till pressure was drained manually...

It ended up being the wrong brake fluid for that original hose....


Anyway I really do not think this apply on this issue....

 

[wdchyd]

It is not off base, I have had a similar thing happen to me on an old SAAB car...it was the flex hoses connecting to the front wheel disc brakes that had collapsed inside lining ....and the inside lining started working as a check valve...and brakes didn't release....stuck till pressure was drained manually...

It ended up being the wrong brake fluid for that original hose....


Anyway I really do not think this apply on this issue....

Funny, I just heard of this happening on a friends Ford Taurus......same problem.....brake fluid not compatible resulting in internal swelling of inside liner thus closing off flow...."Check Valve".....