Tips for clutch master/slave cylinders?

[spacecad3t]

Got a leaky clutch master. Everything I read says just replace the rubber-hard line and slave. I don't see any leaks from the line or slave cylinder. I picked up all 3 and a power bleeder.

Any experience/tips for this one?

[O875]

Often if one (master or slave) is leaking or on its way out then the other isn't far behind, so often both will be done at once to save doing the other soon after.

Perhaps the same idea is behind the rubber-hard line replacement.

[Wespa]

If you have no idea whether all the components were already replaced at some point then it's about time to do so. Trust me, you'll only want to bleed the clutch once, it's a pain even with a Power Bleeder.

[whalenlg]

Make sure to keep the fluid reservoir topped up - there is a divider in the middle between the brake and clutch ports and bleeding the clutch will drain the front half faster - it may look like there’s enough fluid, but air gets sucked into the clutch side.
Also - my master failed right after a clutch replacement, so that’s also a good time to replace master and slave.

[cda951]

I was going to ask which year/type of 944 you have, but because you posted in the NA section I will assume you have one of these. The clutch hydraulic circuit can be a pain to bleed because the hard line from the master cylinder is routed above and along the top of the firewall and behind the oil filler/AOS before the bend that takes the fluid down the clutch slave cylinder. This results in air trapped at the high point of the circuit. There are many, many threads on 944 forums over the past couple of decades advocating methods of all sorts for bleeding this circuit. What I describe below is the best method, as long as one keeps the fluid level in the forward portion of the reservoir above the clutch intake hose!

After the initial bleed---can be pressure or vacuum bleed, reverse bleed, manual, etc---there will likely still be air trapped at the high point of the circuit. The solution is to grab a pair of 11mm wrenches, one being a quality flare-nut wrench (this is one instance where paying the big bucks for Snap-On is key, see first pic), stuff the area with rags, and use a helper or a pedal prop (the latter is my go-to, see second pic, I'm usually working by myself at the shop on an evening or weekend) to hold the clutch pedal down, then crack open the union shown at the top of the firewall. You will likely see and hear air bubbles escaping. Tighten the union, lift the clutch pedal by hand, hold it down again, rinse and repeat.

After 4-6x of this process, all the air should be gone. This works EVERY time.

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