Ok I pulled out the top pistons and re-filled the reservoirs and re-installed everything. I also re-bled the lower plunger ball valve for S&G and got a few more tiny air bubbles out - I guess leaving it overnight helps any little air bubbles make their way to the top of the oil.
You can now clearly see the top of the piston just below the steel cover, though it is not quite as high as the image I stole from the other thread. There is about 2mm of drop available in the steel plate on the spring before it hits the top of the piston (or the spring binds, whatever it is). It is impossible to bleed the reservoir without creating some drop in level.
I re-read my Haynes manual and it says
Quote:
11. Secure the tensioner in the vice at an angle as shown in Fig. 1.31 and fill the upper part of the tensioner housing with engine oil. (note : 1.31 shows tensioner at angle of 20 degrees off vertical)
12. Install the new 'O' rings, and then press the oil retainer piston onto the plunger shaft. Open the bleed screw and depress the piston until it is well down the housing then close the bleed screw.
13. Install the spring, the spring retainer and the cir clip.
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This is the complete opposite to what I have since found out I should have done. To me this is pretty clear - you fill it up, open the bleed and push it down. This is why I did it the way I did. Seems like Haynes is completely wrong.
After doing it again, the instructions should read "Fill the upper part with engine oil until it is overfull. Place on the piston and fit the circlip. Place the Tensioner in a vice at a 20 degree angle and bleed by exerting pressure on the piston. It should then say 'the piston should be visible at the top of the tensioner just under the spring retainer'.
Anyway...hope my trial and error helps other people going down this path for the first time.
Hmm. I just had a thought. Maybe the secret to bleeding them is to leave them upside down and sideways with bleed screw up so all the air rises to the top of the reservoir? However, I don't really see the problem with air in the reservoir as it doesn't provide the damping force, that is achieved by the ball valve in the plunger shaft.