The following is an explanation on how to re-grease a strut with a piggyback canister.
Step 1: Removing the Top Mount
The type of top mount depends on the type of car the shock absorber is fitted to. Although it will almost always be removed the same way. Right at the top of the strut there will be a large nut. In the case of the Suzuki Swift (as shown) it is 27mm nut. Use a rattle-gun with a 27mm socket to undo this nut. Be sure to note that the tapered side of the nut is facing down. Once the nut is removed, simply lift off the top mount. In some models there may be a ring of foam underneath the top mount. This is a breather, simply remove this as well.
Step 2: Removing the Spring
Make sure that there is no preload on the spring. If there is preload, firstly take a measurement of where the spring seat is located, loosen off the locking 3mm grub screw that is in the side of the bottom spring seat and then wind the spring seat down until the spring has no tension on it. If the spring seat reaches the bottom of the thread and there is still significant tension on the spring, spring compressors may be required. Now that the spring is not holding tension against the top spring seat, push the spring seat down and an external circlip will be revealed. Turn the shock around until a small cut-away section is found that allows a small screw driver to get in behind the circlip. Use the screwdriver to lever the circlip out of the circlip groove and remove it from the shock completely. Now simply lift the top spring seat off, followed by the spring.
Step 3: Remove the Shaft cover
Now a 30mm nut on top of the shock is now visible. Use a rattle-gun with a 30mm socket. Once that is removed, the large chrome tube can be slid up and off.
Step 4: Remove the Strut Case
Now turn the shock up the other way. There are 12 M5x.8 Cap-head bolts holding the piggyback to the strut case. Use a 4mm allen key to undo each of these bolts.
NOTE: It is preferred that the shock is held the way that it is shown in the pictures below, and make sure you hold onto the strut case as once all of the bolts are removed, the strut case will be free to fall down off the shock.
Once the 12 bolts are removed, life the piggyback (which is attached to the rest of the shock) up and out of the strut case. There is a small amount of gasket sealant on these faces, so you may need to give the shock a couple of light taps with your hand or a nylon hammer upwards to break the seal. Once the seal is broken, lift the shock out of the strut case.
Step 5: Re-greasing and oiling the Strut Case
As shown below, there are two bushes in the top of the strut case. Firstly make sure that there is no dirt or water in the strut case. If there is, pour the water out and clean the dirt out completely. The existing grease may need to be wiped out with a rag or washed out with something like kerosene or brake clean. Before it is reassembled, you need to make sure there is grease filling the gap between the two bushes. If you need to add more grease, or it has been removed during cleaning, MCA Suspension uses Penrite Moly Grease EP 3%, but any type of grease is better than nothing. Taking something long and straight, preferably with an edge to it, something similar to a 300mm metal ruler, scoop some grease onto the end of it and then wipe the grease into the gap between the bushes until it is full. Try not to damage the Dirt Wiper with the tool that is being used. Also wipe some grease below the bottom bush. In addition to this, a thin film of grease should be wiped into the large chrome tube that was removed earlier. Once the strut case is re-greased, slide the piggyback and shock assembly back into the strut case. Try to make sure the surfaces that meet are clean and if you have any gasket sealant it would be good to apply a bit of this to these surfaces to help them seal. Once the surfaces are clean and some new gasket sealant has been applied (if you have some) screw all the 12 bolts down finger tight and then tighten firmly using a 4mm allen key. Now turn the shock back up the other way so that the shaft is pointing upwards. There will be a small gap between the strut case and the body of the shock. Pour about 50cc of engine oil or similar down this gap. Try to pour it around the body of the shock so that it is evenly spread around and not just down one side.
NOTE: The gasket sealant that was suggested earlier is to help seal the oil inside. If you do not have any sealant, it is not a major problem, however it may mean that the oil may slowly seep out over time.
Step 6: Re-assembling
Now slide the large chrome tube back over the shaft and then down in between the shock body and the strut case. Turn the chrome tube until it locates and locks in with the two flats that are at the end of the shaft. You should feel it lock in and drop down another few millimetres. Make sure that these are locked in together before proceeding. Once you are confident that the tube is located on the shaft correctly, wind the 30mm nut down and use a rattle-gun and 30mm socket to tighten. Now that the 30mm is tight, slide the spring back over and sit it on the bottom spring seat. Now put the top spring seat on top of the spring, push it down out of the way so that the circlip can be refitted. Once the circlip is sitting in the circlip groove correctly, adjust the bottom of the spring seat back up to its correct position that you measured earlier. Finally put the top mount on, followed by the 27mm nut and tighten it up with a rattle-gun.