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How To Dismantle, & Reseal a Hydraulic 

Cylinder 20 Steps to avoid mistakes.

1. Clean the cylinder in wash bay to remove oil, grease and dirt. 

Before commencing disassembly have your mobile phone or digital camera ready and take a picture each step as a part or component is removed. 

2. Set up cylinder to be clamped in the floor vice, with the exception of small convertible type cylinders DO NOT clamp cylinders on a bench mounted vise. Try and clamp the cylinder on the flat part of the clevis, if this is not possible use an appropriate sized rod or pin and clamp the pin in the vise and place end of barrel onto the pin.

3. Finally Level up and support gland nut / rod end of the cylinder on sturdy blocks of wood.

4. Whenever possible try and remove excess oil from both sides of barrel by extending and retracting the rod, collect all waste oil in suitable containers and empty into waste oil drum for future collection by approved registered waste collection company.

5.  Place oil container underneath gland nut to collect oil from cylinder when dismantled.
Important this is one of the most important and potentially time consuming steps so preparation, selection of the most appropriate tools and attention to detail is paramount. 

6. Identify style of gland nut and use appropriate tool to remove gland nut from cylinder.
Check for locking tabs or grub screws on gland nut, e.g.  Yanmar has locking tabs  , JCB cylinders have grub screws. 

7. Most cylinder gland nuts are threaded into the barrel and need to be unscrewed counter clock wise (caution) threaded gland nuts can be extremely tight so some care as well as perseverance is required. 

Typical Screw in Gland Nut

Removed Screw in Gland Nut. This Gland Nut is Damaged. 

8. At this stage take a couple of Minutes to Check for Grease nipples lubricating the rod and barrel clevis pins. Always remove and clean out grease points to ensure that grease can get to the pins as sometimes hardened bushes rotate in a dry swivel connection and the grease way  gets blocked,  Always replace grease nipples with new ones.

9. Remove rod assembly from barrel and collect any oil that comes out in oil tray.

10. Remove barrel from vice and set up rod in vice.
Before attempting removal of piston take a picture with your phone or tablet so you can check which orientation to put it back together.

11. Check for grub screws or scotch keys in piston or nut retaining piston, screws may be under seals.  Identify style of piston or piston nut and use appropriate tool to remove piston from rod.
 Take picture of seals position and location on gland and piston so you know which way to put them back in.

12. Once gland nut and piston is removed from rod start to remove seals from both gland nut and piston carefully as you will need samples to measure up and order.(DO NOT BREAK ANY)
 Keep all old seals in a plastic bag to show customer what has been removed and replaced.
 Don’t assume just because 2 cylinders look identical that they have the same seals. (Speaking from experience)

13. Once all seals wear bands and or bushes are removed use telescopic gauges (internal caliper ) to check bore of barrel in several locations. (check three places at bottom of barrel, three places in middle and three places at end of barrel.)

14. Also measure rod and put a straight edge on a rod to check for any damage. (Damage consists of rust marks, dents, scratches, plating removed.)
 If either part has imperfections (scratches/ dings) then repair or replace. If not possible then order new cylinder.

15. SEAL, WEAR BAND AND GLACIER BUSH MEASURING (if the clearance is more than 0.04mm between glacier bush and rod, will have to machine or press out the glacier bush)
After seal removal, search ‘grid for seals” in MHF folder, if cant be found look on Job card wall.

16. Measure seal and wear band grooves metal to metal only. Draw & label sizes on grid paper. Put your name, date & job on grid paper
Scan & email with order number. Don’t fax.

17. Measure up seals and seal grooves then order a new set from either manufacturer of cylinder or from reputable seal supplier. (Ensure parts removed are correct for the job). Compare dimensions with part numbers and with sizing of components.

18. Check all components for dimensions before re assembly.
 Put gland nut and piston in lathe and use emery paper to clean all rust and marks from both (Make sure to clean all surfaces, especially where seals sit).

19. If applicable put parts in wire wheel to remove any imperfections.
 Once all clean re install seals in both gland nut and piston.
 If using one piece Teflon seals hold seals tight to piston with piston ring compressor or a hose clamp and piston assembly in a plastic bag and then into freezer for 20 mins this will shrink Teflon seals and make them easier to install.
 Oil up and install gland nut on rod, lock tight piston on if held on by nut.(Remember to put piston in the correct orientation, to prevent damaging piston seals. CHECK PICTURES YOU HAVE TAKEN WHEN  PULLED APART)

20. Oil up barrel and install rod assembly into barrel and tighten gland nut.
 Put cylinder on test bench and pressure test in both directions, retract rod all the way in and plug the piston side of the cylinder. Pump oil into the rod side and check for bypass.
If all ok then clean up, put Mobile Hose Fixers sticker on the cylinder and bill customer for professional job.(Remember to also bill clean up time after job is finished)

We have been offering a hydraulic cylinder reseal and rebuild services for about 9 years now and we thought we would write about a couple of particularly interesting jobs we started to work on in our new larger heavy equipment Hydraulics Workshop in Nerang,  Gold Coast Australia last week. 

Our Nerang Workshop Manager Denis with Our Biggest 

Hydraulic Cylinder Reseal To Date 

a 3,000 mm Stroke 250 mm Bore Monster weighing in at 2300 kg.   

Need a Hydraulic Cylinder Resealed or Rebuilt please click here

Also this week one of our clients who business has grown incredibly rapidly, recently purchased mobile compactor for his document destruction business. We gave its hydraulics systems and hardware a health check and prescribed overhauled Hydraulic Pumps and we also rebuilt some of the numerous compactor hydraulic cylinders with new rods and seals.

Hydraulic Cylinders or Hydraulic Rams are found on great majority of equipment.

On earth moving equipment they are designed to be STRONG and to work in the worst conditions imaginable, that is, in dirt, rocks, dust and mud and at pressures up to 270 BAR (4000 PSI).  So most cylinders will only come apart if you are equipped with all the special and necessary tools required to literally force these components apart.

Typical  Cross Section of Hydraulic Ram or Cylinder.  

This particular cylinder below is off a 7 ton Kobelco excavator, it has completed about 4000 hours of work, it has a 100 mm Bore, 850 mm Stroke and 55mm Rod diameter.

Generally there are 2 parts where a large Force is required to dismantle a Hydraulic cylinder.

1. Unscrewing the Gland nut on the end of the cylinder. These usually come apart .... eventually with the use of a correctly sized "C" spanner (or Pinned Cam tool) and a long bar for leverage.
The exception are some Yanmar Cylinders that are made to such close tolerances that the threads usually seize or bind up after a turn or two, .... then... liberal amounts of heat (enough heat to usually melt the seals!) and lots force are required to unscrew them.

Gland Nuts usually screw onto the end of a cylinder's Barrel
and are then done up very tightly.

 2. Unscrewing the nut that holds the Piston onto the Piston Rod.
These nuts are usually done up extremely tight as the piston is the component that has very large forces acting on it in alternating directions of each in/out cycle of the cylinder.

Piston Nut Assembly these Strong Steel Pistons usually screw on to the end
of the Cylinder''s Hardened Chromed Rod .

On the Kobelco cylinder despite all our efforts (including heat) we could not undo the nut. The 300 KG steel bench was flexing and creaking under the strain! We could apply more force but we knew the bench could not handle it and would flip or tip over under the high torque we would need to apply.
Bolting the bench to the floor was not an option as its construction was designed for high weight and it was on wheels so large twisting forces were not an option.

Time was now a critical factor as the customer was picking up the cylinder the next day, So we quickly bolted a 2 meter long steel beam to the concrete floor and then bolted a 200 mm steel vise to it.

We still use this floor beam and 200mm vise to dismantle some of the 

smaller cylinders that come through our doors with great success. 

We then tried again and our floor mounted beam and vice worked a treat!

By our calculations we applied around 4500 NM (3300 foot pounds) of torque to the nut before it came loose.  To put it into comparison the typical torque spec to properly seat a crankshaft balancer on the Chev LS1 V8 engine is 330 NM (240 foot pounds) of torque.

Denis Checking out next acquisition a
massive Hydraulic Cylinder Breakout Bench 

Cheers and all the best for 2019 !

From the team at Mobile Hose Fixers & Hydraulics,

"Living and Working the Dream" on the sunny Gold Coast, Australia.