OK just a little update.
I did replace the original tensioner without compressing, and it worked fine. A little bit of chain noise for about 10 seconds until the oil filled the Hydraulic tensioner, then it quitened down a little. Allow the engine to gently idle for a few minutes for the oil to flow around.
Then took the car for a test drive, but I wasn't too happy with the engine sound. Subconsciously I was also quite worried about the TCT, so didn't dare high rev the engine (> 4K RPM) .
To provide some solace, I replaced the tensioner with a new M44 Febi Bilstein replacement (~£20 from ECP), but this time with the tensioner compressed (as it is supplied). One of the recommended means of decompressing the TCT post installation, is to rev the engine to 3000 RPM for about 20 seconds
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No thanks, that's not really solace, more like Russian Roulette. Instead, I opted for the hard work/safer option approach. Remove the Engine/valve cover, gently push the loose timing chain against the TCT, and pop ! (
actually it was a click). The TCT decompresses safely in the engine, tightening the timing chain. Replacing the engine/valve cover, carefully checking the gasket is seated properly above cylinder 4, and retightening.
After starting the car, there is a few seconds of timing chain noise, then gradually less chain noise.
Again a gentle idle for a few minutes, followed by progressively higher revs. As Flametail will hopefully report, as long as you are careful, changing the TCT shouldn't be a difficult task.
MB7