Dump truck cylinder leaking only at bottom of travel.

[lennyzx11]

I have a 81 Chevy c60 dump. Description of system below.
I got it this way from someone.

What would cause fluid to gush out of the cap end around the rod only during that last few inches of downward travel of the dump?
It raises fine, holds overnight, and comes down also.
No leaks going up or even deadheaded a second at max extension.


It is Pto driven hydraulic with two levers. One for pto on or off.
One center is off/hold and push one way for up and the other way for down.
It has a 2 hose cylinder on it telling me it is double acting.

Before I tear the cylinder down I wanted to ask if maybe something like a valve may not be letting fluid return quick enough and getting pushed out.
I tried power down and gravity down positions but same symptoms.

Thoughts?

 

[wdchyd]

Is there a breather cap on top of cyl at the rod end and another hose connected to a port on the bottom underneath also at the rod end? If so your cylinder is single acting and they are using the front half for a reservoir to feed the PTO pump.
if the breather is gushing out at end if stroke you could be experiencing foamy oil from air entrainment (bad pump shaft seal or suction line), or if hyd rod is leaking only when down it would leak only when reservoir level raises above the rod gland.
Look under to see if you have that breather cap on top of cyl.

 

[lennyzx11]

 

[lennyzx11]

It doesn't appear to have a breather on the cap end. It's not spraying out under pressure but being "displaced" it appears. The oil is not foamy or aerated. The reservoir is mounted below the cylinder under the frame rail while the dump cylinder is mounted on top of the frame. I filled the reservoir to the full mark with the dump bed down and cylinder contracted. I've cleaned it off to find a identifying number or name but no bueno so far.

 

[wdchyd]

Yep, standard double acting like you said.
Maybe a bent rod? (Just guessing)
The style I was thinking of doesn’t have the separate reservoir tank like your Williams PTO pump.

 

[bindian]

A flat (low) spot in the chrome could allow fluid to leak locally and not elsewhere.
hugs, Brandi

 

[lennyzx11]

Yep. Everything is pointing to an internal issue in the cylinder. I’ll pull it out and tear down.

It puzzles me that since the cap end of the cylinder is getting larger in volume as the rod compressed into the barrel why fluid then leaked and not pressurized.

I was thinking something along the lines of the control valve leaking or blocking return across itself or overfilled causing fluid that’s supposed to be going into the reservoir tank being pushed into that cap end of the cylinder and coming out the wiper seal .

I’ll disconnect the cap end line and drain into a bucket and see if return fluid is being pushed into that end during the dump travel down. It “should” be going in the tank.

Then out she comes.
Not the first time I ever overthought a problem!
Lenny

 

[lennyzx11]

Well off to a slow start. I found the retaining pin and drove it out somewhat easily. Then the fun started. The cap end mounting pin is frozen in. Off an on through the day spent soaking it with seafoam penetrating oil and beating on it to no avail.
Dug my little cutting torch out to heat/persuade it but the oxy tank was empty. So off to air gas for oxygen, acetylene, argon, and mix for the mig. Left there 200 bucks lighter.
Work calls kept me from tackling again today other than soaking it with pen oil and giving it a few half hearted smacks with the hammer every now and then.
Get after it again tomorrow.

 

[bindian]

Aren't dumptrucks fun to work on. Hope you got it blocked up well.
hugs, Brandi

 

[Tinhack]

Could just be a bad seal. It looks like it's being extruded in your first picture. (Just below the bolt head.) That or the piston is so badly worn, it can't support the rod and crushed the seal.