Clutch problems... which is faulty master or slave cylinder... or maybe both?

[genphreak]

My M50 powered 525 clutch is feeling very strange- friction/pressure is interrupted only when you press it right in.

A month after I noticed this the gearbox began having trouble syncing gears on hot days. I imagine the clutch fluid is thinner so pressure control reduces enough that the pressure plate is no longer moving away from the clutch plate enough.

Is it likely to be be the master or the slave cylinder going bad? Or should I just do both?

Thanks in advance, Nick

[Bill R.]

You need to inspect the master and the slave for signs of leakage to determine which one is bad....If your having trouble with the gears you should be able to pump the clutch pedal a few times then try the gear change... if that works then you have air in the system and should look for seepage as i stated above , under the dash at the master and down at the transmission on the slave, you may have to unbolt the slave to see the boot for signs of leakage.

[genphreak]

Thanks Bill, I'll check it soon. Got the wires on the trunk of the touring to do too. Will be outside enjoying myself for a while!

[genphreak]

You need to inspect the master and the slave for signs of leakage to determine which one is bad....If your having trouble with the gears you should be able to pump the clutch pedal a few times then try the gear change... if that works then you have air in the system and should look for seepage as i stated above , under the dash at the master and down at the transmission on the slave, you may have to unbolt the slave to see the boot for signs of leakage.For now I left it all in situ and simply bled a lot of fluid through as it didn't come clean for some time. PO used DOT4, but its now using Super DOT4. Not sure if the seals don't like that fluid.

Used my trusty pressure bleeder to positively push the fluid down from the reservoir. Clutch operation feels better and the problem is solved (for the time-being). Will have to see if any more bubbles get in there.

I didn't noticed the jammed gearshift responding to pumping, but that's good advice- thanks Bill. Might be useful if it happens again. Will source some new seals and do a full removal, inspection and re-fit later- when I get the time.

[TechnoWeeny]

For now I left it all in situ and simply bled a lot of fluid through as it didn't come clean for some time. PO used DOT4, but its now using Super DOT4. Not sure if the seals don't like that fluid.

Used my trusty pressure bleeder to positively push the fluid down from the reservoir. Clutch operation feels better and the problem is solved (for the time-being). Will have to see if any more bubbles get in there.

I didn't noticed the jammed gearshift responding to pumping, but that's good advice- thanks Bill. Might be useful if it happens again. Will source some new seals and do a full removal, inspection and re-fit later- when I get the time.
Genphreak, You mentioned you used a pressure bleeder. Mine recently met it's maker. Out of interest which one do you use or recommend for the E34?
Regards,
Warwick

[genphreak]

They're hard to get.... I've a Sealey but there is also a Motive that is popular:

79847986
The pump on the Sealey uses an aluminum shaft- If the Motive's is plastic maybe it is not as good- but I haven't seen one yet. With either the trick is not to use too much pressure to push the system's fluid out- old reservoirs can be surprisingly brittle and brake fluid is not what anyone wants sprayed all the place.

[TechnoWeeny]

They're hard to get.... I've a Sealey but there is also a Motive that is popular:

79847986
The pump on the Sealey uses an aluminum shaft- If the Motive's is plastic maybe it is not as good- but I haven't seen one yet. With either the trick is not to use too much pressure to push the system's fluid out- old reservoirs can be surprisingly brittle and brake fluid is not what anyone wants sprayed all the place.

Thanks Mate, looks like I'm going shopping :-)

[BMWFatherFigure]

A quick check - ease back the dust boot on the master and slave. Any fluid there = rebuild. I use Castrol GRR grease on my brake and clutch rubbers during rebuilds. I believe it helps.