Cat 420D cylinder tube scored...

[NCman]

As above my 2002 420D IT dipper cylinder has been drifting on me and I have had to use it as is due to schedule of house build including footers,septic etc.

I finally got the cylinder off and took it apart. First thing I found was that the piston has wear marks and scrapes/gouges. The seals are worn and even torn. Then looking at the bore there are score marks from one end to the other all parallel to each other and about 1.25"'s apart. I did not find a lot of metal but I did find one curled up piece about 1/8" wide and 2" long. It was all curled up like a chisel would make a wood curl.
Basically, a local cylinder guy said he could not hone the cylinder, redo seals and guarantee the work. I asked about oversized seals and he said there are none. Just 4.5" and the next size of 4.75". I would need to have 1/4" removed for that seal to work.

1)Does anyone have advice besides buying new tube and machining/buying new cylinder?
2)Are there such seals like 4.5" (60-80 over)
3) Is there some area I need to clean out or look at like a poppet valve, relief valve I heard mentioned? If so where is it located and any ideas how to or links?

Thanks,Dan

 

[Grady]

If you want it to work like it did when it was new, new parts are probably the way to go. Here is some info from the website http://www.machinerylubrication.com/Read/570/hydraulic-cylinder

Barrel
Inspect the barrel for internal pitting or scoring. If the barrel is pitted or scored, the effectiveness and service life of the piston seal will be reduced. Therefore, the barrel must be honed to remove damage or be replaced. On small diameter barrels, pitting or scoring less than 0.005 inch deep can be removed using an engine-cylinder honing tool. The barrel must be honed evenly along its full length.

The maximum bore diameter for standard-size piston seals is the nominal bore diameter plus 0.010 inch. For example, if the nominal bore diameter of the barrel is 2.5 inches then the maximum size after honing should not exceed 2.510 inches. This size should be checked at several points along the barrel, using an internal micrometer.

If scoring or pitting is still present at 0.010 inch oversize, the barrel must be honed further to accommodate oversize seals or be replaced. Manufacturing a new barrel from honed tubing is usually the most economical solution for small-diameter cylinders.

Large diameter, inch-size cylinder barrels can be salvaged by honing either 0.030 inch or 0.060 inch oversize and fitting the corresponding oversize piston seals. Oversize seals for metric-size cylinders have limited availability and therefore it is not always possible to salvage metric-size barrels by fitting oversize seals.

Piston
The pistons of cylinders used in light-duty applications are usually machined from aluminum alloy or cast iron and operate in direct contact with the cylinder bore. Minor scoring on the outside diameter of the piston is not detrimental to the function of the cylinder, as long as the minimum diameter of the piston is not less than the nominal bore diameter minus 0.006 inch. This can be checked using an external micrometer. For example, if the nominal diameter of the barrel is 2.5 inches then the minimum piston diameter would be 2.494 inches. If the piston diameter measures outside this tolerance, it must be replaced with a new piston machined from a similar material.

Nonmetallic wear bands are fitted between the piston and barrel, in applications where there are high loads on the rod. If the cylinder is fitted with piston wear bands, these should be replaced as part of the repair.

Ordering Seals
When ordering seals from a seal supplier, avoid the common practice of measuring the old seals. Seals can either shrink or swell in service, or an incorrect seal may have been installed previously. To ensure that you are supplied with the correct seals, measure all seal grooves with a vernier caliper and give this information to your seal supplier.

 

[Bls repair]

You could try to find used ,but don't know what you will get. Best bet is to buy new ,sorry.

 

[NCman]

Thanks for the info guys. Yeah I thought that I might have to buy a new one. I can get the complete cylinder ready to install for 1200+/- or I can let a local guy do what he suggested. He said he could cut off the tube,weld in a new one make all the treading and bevels for the gland... and install a new piston and seal kit for less than 1200. With all that work I imagine his quote next week will be a bit less but then who knows if the rod is bent and such. This is a cylinder that had the rod head break off a few months ago when I whipped the hoe after breaking free from some granite/clay. I imagine that's why it scored up the cylinder and piston. As much as I hate to spend 1200 I think I may have to just bite the bullet and know that the cylinder can be ruled out if there are more issues after installing....

 

[NCman]

If someone can answer #3 that would be great.

Thanks

 

[Delmer]

You had loose metal in the system, and you want somebody to tell you where it went???

The only thing I might do is to take those hoses off of the valve body, blow them out with air and maybe even a bit of sponge. Look in the ports and remove anything obvious. The check valves will be on that valve spool if you want to take them out to inspect, don't change the settings. Otherwise the metal would be back in the tank, hopefully to stay there.

 

[Nige]

Slightly less than $1200 for a replacement barrel then all the doubts regarding the unknown quantity that is the rod, especially in view of what you say above regarding how the damage to the cylinder probably occured in the first place ....
I think I'd be biting the bullet and buying a complete new cylinder. Try Offroad Equipment www.offroadeq.com/ for a price, they can often beat Cat dealer prices for genuine parts.

 

[NCman]

You had loose metal in the system, and you want somebody to tell you where it went???

The only thing I might do is to take those hoses off of the valve body, blow them out with air and maybe even a bit of sponge. Look in the ports and remove anything obvious. The check valves will be on that valve spool if you want to take them out to inspect, don't change the settings. Otherwise the metal would be back in the tank, hopefully to stay there.

Thanks for the advice.

 

[NCman]

Slightly less than $1200 for a replacement barrel then all the doubts regarding the unknown quantity that is the rod, especially in view of what you say above regarding how the damage to the cylinder probably occured in the first place ....
I think I'd be biting the bullet and buying a complete new cylinder. Try Offroad Equipment www.offroadeq.com/ for a price, they can often beat Cat dealer prices for genuine parts.

The best deal I can find is one from hydraulic works with a 90 day warranty for 1340.00 shipped. They are pretty big from what I can tell and do leak test and such. I'll check and see what quality they are before buying.

 

[Welder Dave]

$1340 seems cheap if it's a good quality cylinder. A bet an original Cat cylinder would be more than double that. I spent about the same amount getting the stick cylinder repaired on my hoe when the bolt for the piston ripped the threads out of the rod.

 

[NCman]

$1340 seems cheap if it's a good quality cylinder. A bet an original Cat cylinder would be more than double that. I spent about the same amount getting the stick cylinder repaired on my hoe when the bolt for the piston ripped the threads out of the rod.

Tried to find reviews and found none. Usually there will be some kind of feedback for a company...

Anyone have experience with online hydraulic cylinders?

 

[funwithfuel]

I would look at the lack of feedback as a good thing. Lets face it, we're not facebook kids who gotta post bout every little thing. But if someone gives you a crap product, terrible service or something of that nature. You're gonna post that.

Thats the way i look at feedback. No negative, equals good

 

[NCman]

I would look at the lack of feedback as a good thing. Lets face it, we're not facebook kids who gotta post bout every little thing. But if someone gives you a crap product, terrible service or something of that nature. You're gonna post that.

Thats the way i look at feedback. No negative, equals good

Thanks, that's a good point.

 

[NCman]

I ordered the HW replacement stick cylinder. I called and talked to them before ordering asking a few questions. I asked where they are made and they are made in Ohio by a company that specializes in building replacement cylinders for the majority of brands and models. I asked if it was turn key and he said it was ready to install with bushings already pressed in and zerks... I ordered it Tuesday and he said it will probably be here by Friday. It's coming via freight as it's over the ups limit at 156lbs. I'll update with pics and opinion after install.

 

[irncwby44]

As to ? #3 what we do at our shop when something like this happens is to: 1. Remove and flush the hyd lines from the valve to the cyl. Remove the valve body itself and any valve "down" the flow to the hyd filter and flush them with diesel and air in a large diesel filled conta yu ner. Then drain and replace the valves. After that the hyd tank is drained and the hyd filter replaced. You can also cut open the old filter to Guage how much it caught vs. How much was lost from cyl.

 

[irncwby44]

As to ? #3 what we do at our shop when something like this happens is to: 1. Remove and flush the hyd lines from the valve to the cyl. Remove the valve body itself and any valve "down" the flow to the hyd filter and flush them with diesel and air in a large diesel filled conta yu ner. Then drain and replace the valves. After that the hyd tank is drained and the hyd filter replaced. You can also cut open the old filter to Guage how much it caught vs. How much was lost from cyl.

Container......stupid mechanics fingers.

 

[NCman]

As to ? #3 what we do at our shop when something like this happens is to: 1. Remove and flush the hyd lines from the valve to the cyl. Remove the valve body itself and any valve "down" the flow to the hyd filter and flush them with diesel and air in a large diesel filled conta yu ner. Then drain and replace the valves. After that the hyd tank is drained and the hyd filter replaced. You can also cut open the old filter to Guage how much it caught vs. How much was lost from cyl.

Sounds like a thorough course of action. I'll take that advice and thanks.

 

[NCman]

The new cylinder arrived today. It looks fine and correct but the paint looks a little rough from UPS monkeys handling it. I had thought that it would look like a new dime and I would have to paint the hoe but I think it will look just like the rest of the machine.

The only thing that was a surprise is that there are no zerks. I was told they were installed but...not a big deal. Also, I was told I could just re-install the pins and hook up the lines but that's not the case. there is a plastic plug screwed into one end of the tube so I will need to remove mine from old cylinder and install. The other end of the tube has a block of steel welded to the tube with a female connection. I will have to find a fitting that will screw into that and then have the thread size and pattern for my hose on the other end. Nothing is too big of a deal but now I need to run around looking for a fitting so I can install it. I'll ad some pics I took as it arrived and give a short review after installed.

 

[NCman]

Got the new (HW hydraulic works) cylinder installed and it works perfectly. I did have to buy some male to male boss fittings and zerks but the cylinder is working like new.

 

[Grady]

Good to hear it's working well. I think you'll be glad you went with the new cylinder.