Straightening a hydraulic cylinder rod (JCB 212s, backhoe bucket cylinder)

[greg9504]

Hello,

I've got a 2004 JCB 212s (mid size backhoe, about 12.5k lbs). I noticed the bucket dropping when parked, it's leaking. Looking closer it looks like the rod is also bent. What are the chances of bending it back? Not sure how I bent it, but I guess that doesn't really matter... I have a 20 ton shop press. Any suggestions on how to press on the rod without marring the chrome? It's a 40mm rod (1.57"). I read in this thread https://www.heavyequipmentforums.com/threads/cat-311b-excavator-questions.93223/post-1036212 to heat it up in an oven first, but it's too long for that. At best I could bring it inside over night.
Thanks

 

[Tinkerer]

I know very little about JCB's.
But the first thing That comes to my mind is the thumb.
Does it have a relief valve in the hydraulic circuit ? If it does is it set correctly ?
If there are no marks on that bent rod I would suspect it has something to do with the thumb.
I am not advising you on what to do with the rod. If it were mine I would have a new made.
But if the thumb caused it to bend it will happen again and again. IMHO of course.

 

[Coaldust]

I’ve had surprisingly good luck with straightening cyl rods using v blocks and a hyd press. It was pretty common practice at the dealer I worked for. Cat would not give core credit or maybe, partial core credit, for bent rods. So, we straightened them before returning the cores.

Use a piece of brass or copper to protect the chrome.

 

[greg9504]

Does it have a relief valve in the hydraulic circuit ?

The relief valve for the thumb is set so the bucket overpowers the thumb. The thumb has been on the machine for around 9 years now. But I guess it could have contributed. I may eventually go that route but I figured I should at least try. In 2019 I had the stabilizer rods (also 40mm) remade and it was $375 CDN ($300US) a rod back then, plus 3 hours of labour. Hate to think what they'll charge me now.

Use a piece of brass or copper to protect the chrome.

V blocks, that makes sense. I was wondering how to hold the rod. Thanks.

 

[Welder Dave]

Best to use aluminum V blocks or pieces of aluminum/brass in the V blocks and under the hyd. ram. Generally you want to push the rod a little past straight and hold it there for awhile, like maybe 30 minutes or longer. Then slowly release the pressure and hopefully it springs back straight. I've had rods with slight bends successfully straightened. Also mark which side the bend was on and when you put it back on turn the rod 180 deg's.

 

[Kevin Foust]

I have a JCB 214S I bought used. I had 2 rods bent very slightly, actually less than it looks what yours is. One was on the front bucket lift and the other on the stablizer arm. I took it to a local shop to straighten. The got the front bucket lift but broke the rear one. It was hardened. I ended up having to buy a new rod from JCB as their price to make a replacement was about the same money. You are out nothing to try as it is bad anyway. They did not heat either one of mine.

 

[Tinkerer]

You are out nothing to try, as it is bad anyway. They did not heat either one of mine.

That is so true.
I would try it straightening also.
The last bucket cylinder rod I had a shop make was $400.00 US.

 

[oarwhat]

My local hydraulic shop wouldn't straighten rods. They said rods were hardened and dangerous when they broke. I think they were just trying to sell new rods.

 

[56wrench]

Most hyd cylinder rods are only hardened on the outer 2-4mm depending on the diameter. If a hyd cyl rod can bend without breaking or cracking then it can usually be straightened. It just depends who is doing the straightening and how

 

[Billrog]

I've straightened a few the diameter has a lot to do with how successful you are. Shorter stabilizer rods are the most likely to explode when trying to straighten but I've had one done successfully at a hydraulic shop. The one's I've done myself were like the one in the pic. with a 20 ton press. I made the V blocks out of hardwood & a piece of brass to press against. Takes a bit of time and piecence but within a few thou is adequate . Once done whether correct or not I flip the rod over when I reinstall it which some times requires drilling for a new grease zerk.

 

[Kevin Foust]

Most hyd cylinder rods are only hardened on the outer 2-4mm depending on the diameter. If a hyd cyl rod can bend without breaking or cracking then it can usually be straightened. It just depends who is doing the straightening and how

The shop I used said more and more are being completely hardened. I know the stabilizer rod on my JCB was completely hardened. the problem with trying to get hardened steel to go go back is you already have it stretched/fatigued going one way. You have to over flex it so hard to get it to return, it normally doesn't let you before letting go.

 

[Delmer]

Plywood works pretty well for blocks to hold the rod. If you don't have it straight up and down on the bend, it will pop out, but you didn't want to press it like that anyway. If it breaks, it breaks. As long as it's not lifting people, or lifting stuff above people, it's fine. It should never be lifting above people anyway. Getting it up to 120-150 is better than doing it cold, doesn't have to be 3-400 degrees to be softer than freezing.

 

[Welder Dave]

It depends on how much they're bent. If they have a real noticeable bend, then it might be better to replace them. Apply pressure slowly and let it sit under pressure to help stabilize the grain structure. Kind of like torqueing critical bolts. You torque them to a lower value initially and then go back and torque them a little more in steps to get to the final torque value.

 

[uptight excavating]

I have been watching this thread and wondering if I should jump in. Here goes . Anyways I have staightened a few myself and had repair shops straighten larger ones that I couldn't. Have been successful with Case and JCB. The ones that I straightened myself I did right on the machine without taking the cylinder apart. It takes some thought and careful placement of the jack in regards to where the bend is but it can be surprisingly simple. My motivation in most cases was simply economic. Young with a family and no extra $ . LOL

 

[HarleyHappy]

^^^^ Always the best way to do it and sometimes the safest.
I had a cylinder rod pop out of a press once because I didn’t have it stabilized that good.
That was a leaning experience, more set up less work.

 

[greg9504]

Thanks everyone. I started to do the front bucket seals as both tilt cylinders were leaking. Haven't made it past the first one yet. The dreaded JCB piston pin... first was not realizing there was one... at least I was too weak to shear it. Then, I was waiting to get time to go to the fastener shop to get a 3mm bolt to thread into the pin. Now the pin doesn't want to move. Tried a bit of heat. Still no luck. I ran out of time, will hopefully get back to it this weekend.

 

[Kevin Foust]

I honestly like their pin system. I've used just a screw to get mine out and none of them have given me any fits. I'm wondering if someone has been into it before and drove the pin in. All of them I have dealt with were pretty loose and came out quick. Done about 10 of them. Was the cap nut on the tube chewed up before you started? You want to take that end nut pictured off first as it could be putting an end load on the piston.

If you don't know, put the rod pin back in and let the backhoe be your vise when getting the end nut on the rod off.

 

[greg9504]

I believe the nut/piston are one piece?? I'll have to go take another look. Parts schematic below (for the rear bucket curl cylinder, but the front is similar, they use the same seal kit). Part 8 is the "piston head", there's no separate nut. And yes those marks are from me, using imperial 12 point socket on metric nut. In this video you can see he shows the pin, then the piston/nut assembly is all one:

, not the same cylinder but a JCB and it looks like what I have.

Yes, after I got the rod out, I flipped it around and put the pin back in, so it's resting on the front bucket.

 

[Kevin Foust]

I believe the nut/piston are one piece??

You are right. I had a brain malfunction, sorry about that.

 

[greg9504]

One step forward, two backwards. So the pin was stuck because the piston was tightened tight up against it:


So I put my big pipe wrench on with a cheater bar to back it off (I had tried a 3/4" breaker bar).


And as the piston/nut broke loose the pin ejected from the hole. It literally shot out, up a few feet. But not ALL of it came out. Hoping that the piece still in there drops out once I flip it over. So now I need a new pin... fun