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Author: Subject: clutch possible issue
craigdiver

posted on 12/2/18 at 07:11 PM Reply With Quote
clutch possible issue

had trouble bleeding my clutch master / slave on my BMW 2.5 straight 6 - this was mainly through my inexperience.

Eventually got circuit bled but pedal not feeling clutch-like. Read the BMW haynes manual and internet and it was suggested the slave cylinder can just be unbolted and removed (being careful not to pop rod out of cylinder). As it is still exposed it was easy to remove and the actuating rod is flopping about and not sticking straight out but is moving out with the pedal press but needing multiple presses of pedal to get it to extend.

Looked on ebay - new slave £32 - bought as will be difficult to get to if I have issues with it once interior panels fitted. Says the piston is 22.2mm (travel?).

Photo below shows into the hole in my bellhousing to the clutch lever, does this only need 22mm movement to disengage clutch? Can I knock up a bit of threaded rod to push this to release the clutch mechanism?

If the clutch doesn’t release what options do I have for freeing it off without splitting engine/gearbox (I drove the donor BMW to my workshop 18 months ago and was ok then)?









If it ain't broken, fix it anyway (just because).

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rusty nuts

posted on 12/2/18 at 07:48 PM Reply With Quote
22mm will be the bore diameter , it would be possible to work out the stroke if you know the stroke and bore size of the master cylinder
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craigdiver

posted on 12/2/18 at 08:00 PM Reply With Quote
quote:
Originally posted by rusty nuts
22mm will be the bore diameter , it would be possible to work out the stroke if you know the stroke and bore size of the master cylinder


not sure of the original BMW master cylinder but now connected to OBP pedal box with standard hydraulic clutch 0.75 master cylinder (whatever that means but if 0.75” that equates to 19mm).

[Edited on 12/2/18 by craigdiver]





If it ain't broken, fix it anyway (just because).

Building - BMW powered Haynes Roadster/442E hybrid.

Classic Fiat 126 aircooled
Aprilia Mana 850
Chinese 125cc motocross bike

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gremlin1234

posted on 12/2/18 at 09:07 PM Reply With Quote
quote:
Originally posted by craigdiver 0.75 master cylinder (whatever that means but if 0.75” that equates to 19mm).
its decimal fractions of an inch. -
.75 == 3/4 inch
.625 is common too, (5/8th)
as are 9/16th, and 7/8 etc inch

[Edited on 12/2/18 by gremlin1234]

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martin500

posted on 12/2/18 at 09:34 PM Reply With Quote
quote:
Originally posted by gremlin1234
quote:
Originally posted by craigdiver 0.75 master cylinder (whatever that means but if 0.75” that equates to 19mm).
its decimal fractions of an inch. -
.75 == 3/4 inch
.625 is common too, (5/8th)
as are 9/16th, and 7/8 etc inch

[Edited on 12/2/18 by gremlin1234]


i think the BMW master is 3/4" so the same as your pedal box, so 1mm of stroke on your master will equate to about 0.73mm of stroke on the 22.2mm slave

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Mr Whippy

posted on 13/2/18 at 12:33 PM Reply With Quote
pull your old slave cylinder apart and clean the bore with steel wool etc

Lubricate it with brake fluid and put it back together

Put some copper slip on the ball end of the rod and bolt it back on. Best thing to use to bleed is a - Gunson Eezibleed, works great and doesn't need the pedal touched.

Once done and assuming the car runs... jack up the rear wheels (properly) and start it in 3rd gear, rev it up and then jump on the brakes. This jolt will pull the clutch free, sounds dramatic but not bad to the car (unless you have terrible engine mounts)

Make sure you operate the clutch pedal once a month to stop it sticking

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CTLeeds

posted on 14/2/18 at 06:37 PM Reply With Quote
Hi Craig,

I've just done exactly the same on my M52 2.8 for exactly the same reason although it was installed in the chassis when I did it. Just for your information I'm using a .625 master cylinder and a standard slave and I can select all gears as you would expect and have a heavy pedal.

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craigdiver

posted on 14/2/18 at 07:13 PM Reply With Quote
quote:
Originally posted by CTLeeds
Hi Craig,

I've just done exactly the same on my M52 2.8 for exactly the same reason although it was installed in the chassis when I did it. Just for your information I'm using a .625 master cylinder and a standard slave and I can select all gears as you would expect and have a heavy pedal.


Had someone more knowledgable look at the cylinders and all is good with them, will have engine running again in a couple of weeks so will take Mr Whippy’s advice and get car securely on axle stands and start the car in third, get some revs up then clutch in and hit the brakes :-0





If it ain't broken, fix it anyway (just because).

Building - BMW powered Haynes Roadster/442E hybrid.

Classic Fiat 126 aircooled
Aprilia Mana 850
Chinese 125cc motocross bike

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CTLeeds

posted on 14/2/18 at 07:24 PM Reply With Quote
Good Luck! I think I'd ratchet strap the chassis to something immovable at both ends to make sure it doesn't rock off the stands and go through the nearest wall.
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craigdiver

posted on 14/2/18 at 07:39 PM Reply With Quote
quote:
Originally posted by CTLeeds
Good Luck! I think I'd ratchet strap the chassis to something immovable at both ends to make sure it doesn't rock off the stands and go through the nearest wall.


was your clutch seized or was your hydraulic cylinders playing up?





If it ain't broken, fix it anyway (just because).

Building - BMW powered Haynes Roadster/442E hybrid.

Classic Fiat 126 aircooled
Aprilia Mana 850
Chinese 125cc motocross bike

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CTLeeds

posted on 14/2/18 at 07:57 PM Reply With Quote
Neither. Preventative maintenance whilst access was good.
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