Clutch pedal has no resistance occasionally

[Chimmychanga]

Sometimes my clutch pedal will go straight to the floor if I just rest my foot on it with little or no resistance, when it comes up the biting point will be right at the bottom.
Other time it'll be fine and I can drive around with no bother. Sometimes its a bit of both. When it does happen it seems like pressing the clutch a few times and letting it come back to the top will then make it normal again.

I have checked the footwell to see if there has been any leak from the master cylinder as it seems like this is a common prob but all is dry. There is fluid in the reservoir. Any ideas? Could it be the slave?

Cheers

[johnl320]

My money is on, master cylinder piston seal

[Billwill]

Could be the master or the slave but as johnl320 above says...probably the master.
The worn seals allow the fluid to go past them but the fluid does not leave the system.
If the bore of the master cylinder is good...you can buy a kit of seals to re-furbish the master cylinder.....and bleed out old fluid and air!

[randomspeedfreak]

i have the same problem anyone have a part number for this?

[capri_rob]

You can get a new master cylinder off Ebay for about £21.

Compared to the cost of a new BMW one even if it only lasts a couple of years its worth a punt

[Trebor333]

I had a very similar problem with my clutch and I got in the car one day and I had no clutch at all, it turned out it was the slave cylinder. Mind you once that was replaced I found the master was leaking as well. If your going to replace one its probally a good idea to do the other as well.

[capri_rob]

I had a very similar problem with my clutch and I got in the car one day and I had no clutch at all, it turned out it was the slave cylinder. Mind you once that was replaced I found the master was leaking as well. If your going to replace one its probally a good idea to do the other as well.

THIS

Do them both at the same time as if one is fooked the other one won't be far behind it

[Brianmoooore]

The OP's problem will be the master cylinder main seal. If it were the slave cylinder, fluid would leak into the bell housing, and the level in the reservoir would drop until it was empty.
If you replace just the master cylinder, or its seal, the rebuilt cylinder will displace more fluid than before when the pedal is pressed, which will push the slave cylinder piston (and its seal) into a position in the bore where it hasn't been for a while, where the already fragile seal will very likely fail.

[Chimmychanga]

Thanks for all the help. I'll be replacing both the cylinders then. That and my wheel bearing. Some fun times ahead!