Cylinder internal leak?

sony224422 · Jan 14, 2023

I figured a new thread would gather more interest- I have my 1964 ford 4000 fel and backhoe, and am having a weak bucket curl on the backhoe. I put a gauge on the test port and am able to get 2000 psi (relief setting).

I can put the outriggers down and lift the rear of the tractor until the cylinders bottom out and they will hit 2000 psi. I can put the boom down and lift the rear of the tractor off the outriggers and hit 2000 psi when it bottoms out too. I can swing left and right with no reason to think anything is wrong with that either. The pull on the arm seems like it is strong enough, though I’m not sure if I can test it other than it will hit 2000 psi I believe. I plan on testing to see if it will pull the tractor backwards with the out riggers up.
The curl is where I have issues. It will curl, and while there is no load on it, like in the air, it will curl up and hit between 500-700 psi until it bottoms out and then it will shoot to 2000 psi. When it’s in the ground, and I go to curl, it will hit 2000 psi but seems like there is no strength. I can’t scoop a bucket of dirt, or really even drag the teeth through the dirt.

The front end loader easily lifts the front off the ground.

The loader valve is brand new from surplus center, with a power beyond. The loader valve is set to 2000 psi from the factory, supposedly, but I haven’t tested that but don’t think I need to. The backhoe valve is set to 2000 psi too from what I can test and see.

My thought is that I need to take a line off the curl cylinder and see if the fluid is bypassing internally when the lever is worked. Is there anything I should check?

ROUSTABOUT · Jan 15, 2023

I wouldn't have spent all that time checking. Just pull a line off on one side of piston and apply real pressure to the other side of piston. If fluid comes out of cylinder, there's your problem. Get a good flash light and do a visual of the cylinder bore. Make sure it's smooth. Check your rod for any nicks and take care of those. I use a fine file and sand paper. Then take piston off rod and take cylinder cap together to a hydraulic shop and they can match up some parts to fit what you have. That will be a lot cheaper than getting the correct kit somewhere. Basically you get the same kit from a dealer, but somebody in the chain makes a few hundred off you. I've worked at a few dealerships.

TractorTech · Jan 15, 2023

Agree with Roustabout that you found the problem when circuit tested good. The cylinders are pretty simple on those older backhoes. Chevron packing is the norm and a shop can put together cheap OR you can search for kits that range all over the price range if you don’t have a local shop.

Dave M7040 · Jan 15, 2023

The attached procedure will help your thoroughly check out your cylinder. A cylinder can bulge in the middle. In this situation the piston seal will not leak at the end of the strokes.
Dave M7040

sony224422 · Jan 16, 2023

I really appreciate the help and the troubleshooting. I switched lines around just to test the control valves (I have the test manuals and they suggest it and it’s easy enough) and then took a line off the cylinder. I did not get what I thought I would, a little if any fluid really came out. It did not gush out.

I am wondering if it’s just not as strong as I think it would be. I’ve only ever run mini excavators, and they were decently powerful. I think maybe my technique and machine size are just smaller and less powerful than I’d thought they’d be.

TractorTech · Jan 16, 2023

Interesting. Regardless of age and your experience with other machines, it may not be what you have experienced on newer machines, but it should curl and scoop dirt.
What model is the backhoe or do you have some pictures of it?

LD1 · Jan 17, 2023

Wouldnt hurt to test the cylinder. but if you are getting full system pressure I am gonna assume the machine is just weaker than you expect compared to a mini-ex.

I too am curious as to what model the hoe is....and maybe some pics? Maybe the bucket is too big to be effective in the material you are digging, or someones home-brew repair in the past and put on a different (smaller) cylinder.

Also, some of them old hoe's have different pin holes on the bucket for different leverage and range of motion. One will give more articulation but less power, the other will give more power but less articulation

sony224422 · Jan 17, 2023

It’s a 1964 ford 4000 (4140) with the 20 gpm front hydraulic pump. New loader valve with power beyond to the hoe. Ford 712 loader and 723 hoe

TractorTech · Jan 17, 2023

Thanks for the pictures. As LD1 said, there are different holes for different reasons.
Have you tried to to pin the dogbone link onto the bucket back hole? This would give you more leverage.

ROUSTABOUT · Jan 18, 2023

If you got any fluid, you may not have been in the exact bad spot. I would do it with piston near center of travel. That old hoe should be a hoss about digging. I'm in Arkansas and we use machines like that on the regular. It should hang with a new one. I'm saying cylinder needs a packing.