Quote:
Originally Posted by Mattty
I’m not 100% certain so someone may correct me, but is it possible that there is air in the line leading to the clutch slave cylinder? If there is air in the line could it cause a spongy feeling clutch, similar to having air in the brake lines?
I have read that the best way to bleed the clutch system is to reverse bleed it by pumping in the fluid from the bleed nipple on the clutch slave cylinder.
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I can see why you suggest that and to be honest, was one of my first thoughts too. However, that would cause the driven plate to not release because the air would get compressed before any movement on the release lever.
This would cause "clutch drag" making it difficult to engage gears, especially from a standstill.
As for reverse bleeding, horrible idea! Any dirt, contamination or grit present in the hydraulic line would then be pushed up into the master cylinder to destroy the master cylinder seals. Far better to bleed the correct way and expel any contaminants out through the bleed nipple.
This is also true for braking systems and in the case of ABS-equipped cars, particularly so as dirt can damage the ABS modulator leaving you with no brakes at all and a huge bill for a replacement modulator.
Even squeezing the piston back into the caliper to enable new pads to be fitted counts as reverse bleeding. As such, it is best practice to open the bleed nipple 1/4 turn with a one-way bleeder on while the pistons are pushed into the caliper. It's easier on the seals as well so they're less likely to suffer damage from being pushed back the wrong way with pressure behind them.
Once the pistons are back in the caliper, new pads fitted and everything secure, bleeding the effected legs of the system is all that's needed.
Anybody who says they've done it without opening the bleed nipple on an ABS car and has got away with it has been lucky. They have however potentially stored up trouble for themselves and could find the master cylinder fails when they need it most!
Even on non-ABS cars, it's not recommened to simply push the caliper pistons back in without opening the bleed nipples for the same reason.
It might save you a couple of minutes on a pad change but a working brake system will save your life.
