Easy clutch bleeding method

Post by **Vtecmec** » Mon Dec 16, 2013 2:14 pm

wurlycorner wrote: The picture is a standard bleed nipple?
If you unscrew that, it will work exactly the same as a normal bleed nipple?

I think it has a one way valve inside, so it can push fluid out, but will not suck air in (notwithstanding thread leakage).

Post by **Merlin** » Mon Dec 16, 2013 2:20 pm

Vtecmec wrote:If the end of the tube is immersed in fluid, you don't have to close or open the nipple on down/up stroke, just once at the start and once at the end.

I get what you mean now. It would be drawing fluid instead of air.

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Mon Dec 16, 2013 2:21 pm

Vtecmec wrote:I think it has a one way valve inside, so it can push fluid out, but will not suck air in (notwithstanding thread leakage).

Assume so, yep - but the body would have to be split to put the valve inside and the one in the pic just looks like an ordinary one piece lump of metal. So how the hell would you ever know if you've got one fitted or not?

Post by **Vtecmec** » Mon Dec 16, 2013 2:53 pm

Merlin wrote:I get what you mean now. It would be drawing fluid instead of air.

Exactly.

Post by **Merlin** » Mon Dec 16, 2013 3:01 pm

I get the theory but if you had an air bubble only 10% of the way down the line how would that bubble move down the line if every up stroke of the pedal is drawing up fluid? You need to expel the entire volume of the line to ensure there is no air

The only way I can see this method working is if the downward stroke is longer than the upward stroke, but that doesn't happen. Am I missing something?

Supercharged 無限MUGEN BB1 Profile · Post by **nucleustylzlude** » Mon Dec 16, 2013 3:31 pm

???

Confusing much?

As vtecmec says, immersed in a spare bottle of fluid you can pump it through with constant top-ups of the reservoir. This is with the reservoir cap off so the fluid isn't hydraulically sealed as the pedal draws back up it sucks in the fresh fluid from the reservoir - hence the topping up part. It's when that runs dry you run into problems and have to start again!

I just had never done a clutch m/c and never knew the mechanics of one a few years back, I just did it with the advice I was given only to find out my two man job lasting 30mins plus (for changing the fluid before Donald chimes in!) could have been just me on my todd for 5mins like when I do my brakes.

Post by **Vtecmec** » Mon Dec 16, 2013 3:34 pm

Merlin wrote:I get the theory but if you had an air bubble only 10% of the way down the line how would that bubble move down the line if every up stroke of the pedal is drawing up fluid? You need to expel the entire volume of the line to ensure there is no air The only way I can see this method working is if the downward stroke is longer than the upward stroke, but that doesn't happen. Am I missing something?

The down stroke pushes more fluid out than the up stroke sucks up, dunno why, but it does.

Post by **Vtecmec** » Mon Dec 16, 2013 3:39 pm

Thinking about it, on the upstroke, it will draw from the reservoir at the master cylinder as well as at the end of the tube.

Post by **Merlin** » Mon Dec 16, 2013 3:44 pm

That must be the step that I wasn't understanding. So the slave doesn't actually suck any fluid up at all, or much less than during the down stroke? The up stroke is drawing straight from the reservoir on the MC rather than from the slave end.

Vtecmec wrote:Thinking about it, on the upstroke, it will draw from the reservoir at the master cylinder as well as at the end of the tube.

So with enough pumps of the pedal it will both expel all of the volume of the tube and any excess it has sucked up from the slave end.

Got it!

Post by **Vtecmec** » Mon Dec 16, 2013 3:47 pm

For the most part yes. The upstroke will still suck some up the slave, but the majority comes via the MC.