A factor to consider here is the situation where there may be air bubbles in the system. I doubt 'gravity' will provide enough flow rate to encourage air bubbles to be expelled.
Another feature noted when brake bleeding is the sinking pedal phenomenon. It's not been discussed for a long time and it's surprising that relatively few members have observed it. After a bleed, it's natural to press and hold down the brake pedal to confirm the hydraulic lock. So, when you do that, keep your pedal hard down for several minutes and observe if it very slowly sinks. It's a well known effect that many car makes exhibit (including Jaguar) and is not an MOT nor a safety issue. The effect doesn't happen with the engine running. There are several old threads discussing it (search for 'SPP' for some of them). It's reported that SPP is not observed when a T4 is used to bleed the brakes. (This is the basis of my query in Post 6). If that's a real effect and not simply experimental variance/operator bias, then what's the difference in the state of the brakes after each process? I'd love to find a convincing answer.
TC
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