When I removed the rear shock absorbers I thought that they were quite badly corroded.
Once I had removed all of the underseal and dirty off much of the out metal surface was corroded, but not so bad that I thought would affect the structural integrity or performance.
You can see how the metal has become all pitted and rough.
Even so, I hoped that these would be restorable, so I purchased some shock oil and some new gaskets and started to work.
There are two chambers that holds the oil. One is accessed by removing the 6 screws.
The gasket was nearly completely perished and the inside was near black with grime. What oil that was in there resembled metallic grey paint with glitter in it. This is not a good sign.
With some light cleaning it started to look a lot better. Using the new oil I flushed it out a few times to try and remove as much of the grime as I could.
Once I had cleaned this up as best I could it was time to refill the chamber with new oil.
This now looks much better. The oil needs to be filled up to the lowest point of the drain plug bolt which is shown in the top left of this picture. I slightly overfilled mine and then removed the bolt afterwards to set the level.
Before fitting the gasket it is important to clean the surfaces as best as you can. I used fine wet and dry paper.
Once in place you can then refit the lid. As with all gaskets you should tighten the screws from the inside out.
The next chamber is accessed by the lower value bolt.
Here's what I got out of all the shocks and you can see how dirty the oil was. Definitely needed doing.
Once the value bolt has been removed there are these components although it turned out that there was a washer missing from one of the shocks which sits between the spring and value.
Once you have drained and flushed the old oil you can refill the chamber. If you start with the arm in the lowest position and start to fill the oil until the chamber is 3/4 fill, then slightly raise the arm and this will push the oil further into the chamber and the level will fall allowing you to put more oil in. Keep repeating this process until you the level remains the same.
You then have to make sure you get all the bubbles out of the chamber. Keeps slowly moving the arm up and down to work out the air bubbles.
When you are happy that you have all the bubbles out you can slowly replace the bolt. It is normal to have an overflow of oil.
Now hopefully you'll find that when moving the arms you should have a constant and stiff resistance throughout the full range. Unfortunately for me one of my shocks started to develop an issue. When moving the arm I could feel a judder at one point. I rechecked the levels and tried again. The juddering got worse and then the the resistance dropped away and became inconsistent.
This is because the inner piston that has rubber seals have failed, which for me means I need new shocks. I felt I should replace both of them as they are the same age and condition, so the chance of the other failing is quite high.
The front shocks follow the same process so here are some photos to show you how that went. Both of my front shocks were in a much better condition than the rears and have come up very well.
Very dirty old oil
Here is the highest oil level point.
