DC will weak lift

[Grapefarmer]

Is there a rebuild kit for the hydraulic pump? I have to constantly make it lift or it will slowly let the load down (boom pole)

Thank in advance

 

[Wrangler1973]

Try external_link, they should have a kit for the DC hydraulics or John can point you in the right direction for parts/numbers etc. He's a great source of info and Case parts. Here's his number 315-585-9826 or you can look at external_link.com

 

[John Saeli]

Wrangler is very generous w/ his comments, and some would argue, but the fact that your pump will lift indicates the pump is ok. The DC pump is a good solid unit. The problem you describe is either the valve not holding, or a hydraulic cylinder leaking internally. If the cylinder is plugged into the remote couplers, it would be very easy to lift the load, pull the couplers out, thereby isolating the cyl's from the tractor, and if they leak down, it's the cyl's. If they hold, it is the valve. I say cyl's because when you say Boom I'm thinking of a loader.

 

[Wrangler1973]

John your response right there backs up my claims, LOL. You've been a great help to me with parts for my tractors and possible problems I've been having due to my lack of mechanical know how. Others can argue to the contrary but I stand by what I said and I'm sure there are others who will back me up on this.

Gene

 

[mEl]

It is not my intention of disagreeing with John but, if you raise a cylinder clear up with a load on it with leaky packing and unplug the hoses, the cylinder can only drop till the pressure equalizes in the two sides of the cylinder, the reason being that the piston end of the cylinder contains more surface area (oil volume) than the rod end area, when the coupler is disconnected there is no place for the bypassing oil to get back to sum so the pressures equalize and for all intents and purposes it becomes a simple displacement cylinder with only the displacement of the actual rod size being the effective cylinder diameter just like the piston was not there. That is what makes diagnosing leak down on a dual lift cylinder system difficult.

 

[John Saeli]

Mel: What you are saying is true if the piston seal is intact, but if the seal is bad, gravity will bring the load down, the oil bypassing
the faulty piston seal.

 

[Grapefarmer]

Never thought about a leaking cylinder. Thank you all.

 

[mEl]

No John, the piston don't even have to be there except to raise it! the larger displacement piston end has more volume than the rod end because of the presence of the rod and as as soon as the pressures equalize across the leak, the diameter of the rod becomes the piston area in effect and it will stop lowering with the rod end plugged. With the engine shut off, it will then lower in the lever raise position because you have provided a return to sump for the rod end of the cylinder. Being heavy into the utility line as well as Ag I have seen this more times than you can imagine. John, if you need further proof, disassemble a cylinder, remove the piston and reassemble it, plug both ports and fill the cylinder with oil except for a inch or two and then put the rod in the end and see how far you can push the rod in, better yet, put a gauge in the rod end port and see what happens when you force the rod in.

This post was edited by mEl on 04/27/2022 at 04:29 am.

 

[Klyde]

You are right Mel. btdt

 

[mEl]

Thank you Klyde, I have an online site that demonstrates it with pictures but I cannot get it to my computer to mail it. It is not my style to be combative and I am not being that but I have used this as a diagnostic tool more time than you can imagine in 50 + years at this stuff.

 

[John Saeli]

OK. Tell me why my Disc settles, when I raise it up & pull the hoses? Come on Klyde!! You too!!

 

[mEl]

Not going to argue just to make a point and I do not need to defend truth, I have been there to many times and what I am saying is based on hydraulic principles and a study of Pascals Law covers it clearly. if you push the rod into a cylinder as I described hard enough somethings gonna blow and someones gonna get wet with hydraulic oil. the rod moving in displaces oil with no place for it to go! I have said enough and I do not want anyone else to leave this forum. The only thing that will let your disk down is a leak anywhere in the system.

 

[WilBury]

Fascinating...so how do ya test for leaking cylinder pistons? Isolate a cylinder, pressurize one or both sides with gauge(s), & look for changes? Pressurize one end, watch for flow out the other opened end?

This post was edited by WilBury on 04/27/2022 at 06:53 am.

 

[mEl]

Wil, you can test for leaks as others have described, one way I have used successfully over many years is to warm the oil in the system using another function, then load the system in question and hold the lever in raise while feeling the cylinders where the piston will be , if you feel the cylinder getting warm at the piston in one spot, you have isolated the leak, remember, you have two cylinders in parallel on a loader generally and one leaky one will allow both to lower, you could crack a fitting on the rod end of a cylinder and allow oil to escape into a bucket to see if the system drifts down bbut on a parallel cylinder system that will not show you which one is at fault, you would have to completely isolate each cylinder to be certain, you could put a pressure gauge into the rod end port then watch for a pressure rise indicating oil transfer from a larger volume to smaller.

This post was edited by mEl on 04/27/2022 at 07:11 am.

 

[WilBury]

I'll be dog-goned, more than one way to skin a cat, eh?

 

[Butch/ Ohio]

Sorry to dump more oil on the fire, but here's a story to illustrate Me:L's point. As a kid I attended a service training school in Racine and the instructor had a 310G dozer in the room and
showed us. The blade would lift, but as soon as you let go of the lever it would lower to the floor. He then put down pressure on the blade and raised the front of the tractor off the ground he
shut it off and it stayed right there. Now , he said , what do you think is wrong with this tractor. Nearly everyone agreed that the problem was in the valve. No he said. It's got a bad cylinder
packing, in fact,(he showed us a handful of chevron packing), I've taken the packing clear out of one of those cylinders. He then explained that a cylinder with a bad enough piston seal
essentially turns into a one way cylinder

 

[mEl]

Wil , I worked 52 Yrs for a Case dealer and Backhoe/loaders, skid steers ,and all the common series Ag tractors were my life from DCs to the 96 series with the PFC hydraulic systems. I am more than willing to share what I have learned for the preservation of our Case heritage. If you have anymore questions I will be more than happy to share with you and all on this forum.

 

[WilBury]

This forum has become somewhat of an addiction for me now. I like to think I'm still capable of learning, even at my advanced stubborn age. And that goes for comments from [i:b4e78d427d]everyone[/i:b4e78d427d]!

 

[John Saeli]

Yes!! Finally Mel!! The cyl. is leaking by internally, exactly as Butch/Ohio described!! You both have made my point!! I too have over 50
years experience and have spent hundreds of thousands of $$$ at the school of hard knocks and when a cylinder leaks down, and it is isolated
by isolating the cyl from the valve, it has to be leaking by internally. None of us can change the laws of physics & gravity. Thank you both
for finally getting it but Klyde has been strangely quiet!!

 

[mEl]

Butch/Ohio, Thank you for making my point exactly, your illustration brings up another aspect of cylinder volume rod end to big end, In a dozer lift application the blade is being lifted by the rod (small volume) end of the cylinder, with bad packing, because of its weight the dozer blade can fall under gravity and a void is pulled on the backside (Large volume ) end allowing it to drop because the large end of the cylinder can accommodate the rod volume oil coming past the leaky packing. When down pressure to raise the front of the dozer is applied the large end of the piston is being used and the unequal volume thing takes over and the dozer cannot leak down with bad packing due to equalization of pressure big end to rod end of the cylinders. Thank you once again. It is time for me to back out of this discussion and let people sort it out for themselves, if anyone wants to discuss it further I will supply my phone number.

 

[mEl]

To anyone wishing to study this subject further I invite you to go to my Facebook page and look at the online info I have placed there, I will not be posting it here, Thank you, Mel

 

[John Saeli]

Aaww Gee Mel, I don't do Facebook, but I invite you and anyone else to come here, I'll raise the disc, pull the hoses & we'll watch the disc
slowly settle. I'll provide the beer & chairs for while we watch. I understand the science of displacement, but I can't explain it.

 

[WilBury]

I think you all get points for this one.
Sadly, I won't touch Facebook with a ten-foot pole either!
( I do do beer tho!)

 

[Klyde]

WHY would you do that? And if it didn't settle how would you hook the hoses back up? Most cylinders I test don't have couplers so you have to unhook and cap.

 

[Grapefarmer]

Just an update. I put a valve on the up pressure side of the cylinder and lifted the boom and shut the valve and it stayed lifted. So it someting in the pump. But me being lazy, I will just use the valve to hold the load for now. Lol

 

[mEl]

(quoted from post at 19:57:57 04/30/22) Just an update. I put a valve on the up pressure side of the cylinder and lifted the boom and shut the valve and it stayed lifted. So it someting in the pump. But me being lazy, I will just use the valve to hold the load for now. Lol

Just to double check, without starting the tractor pull the lever into the raise position and see what happens, if it stays put the cylinder is ok, if the cylinder has a packing leak it will go down.