I noticed yesterday that the fluid in the clutch master cylinder reservoir had darkened somewhat & that a white film appeared to have formed at the bottom. The car is 20 months old with about 8000 miles on the clock.

Removing the cap & black rubber diaphragm revealed a layer of white semicrystalline sediment. The attached photo isn't the best - it's taken looking down through the fluid - but it illustrates the problem. I've left in in hi-res so you can see the detail - just click to enlarge.

For now, I've vacuumed out the sediment & replaced the fluid in the reservoir, but obviously this is going to need a complete flush. Annoyingly it looks like it's going to be necessary to remove the battery & battery tray to get access to the bleed screw on the slave cylinder.

I'd like to think this is a one-off. I'd be grateful if those of you who know what to look for would have a look at their clutch master & report back. Please only remove the cap & diaphragm if you're sure what you're doing.

Many thanks
John

Looks like the fluid is shot to me

Andy Monty said:

Looks like the fluid is shot to me

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That's a given. What I'm trying to find out now is how widespread the problem is.

Hmmm mine is the same. I would say mine is worse.

Car is 2 years 5 months old with 30k miles on the clock

Probably just debris / contamination from the system, if the clutch works I wouldn't stress about it

RobW said:

Probably just debris / contamination from the system, if the clutch works I wouldn't stress about it

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I'm not too bothered.

I think I might get it flushed and new fluid through it at the next service though.

jrkitching said:

That's a given. What I'm trying to find out now is how widespread the problem is.

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sorry should have made that a bit clearer i ment that the fluid is shot rather than it been something like a deteriorating seal leaving the film behind

Update:

The Panda is similarly afflicted (parts are identical) . 14 months/14k miles .

More photos attached.

On removing the reservoir cap and examining the diaphragm, there are droplets of what appear to be a combination of condensed water & brake fluid, and a small puddle at its base. Removing the diaphragm shows a similar type and level of contamination to my 500.

If you have the right kind of camera, you can take a shot of the underneath of the reservoir, which may show the sediment. Unfortunately one of the A/C pipes runs directly below it & partially blocks the view.

What I suspect is happening is that moist air is entering the reservoir through the breather hole in its cap (it's unusually large for a breather) and condensing out on the inner surface of the diaphragm. The diaphragm has a large surface area & if the clutch fluid is very cold (which it will be after the car has been left overnight in the winter), then any water vapour in the air above it will quickly condense out as liquid. This condensate is then mixing with the fluid, causing it to fail. If you look carefully at the tracks in the photos, it appears this sediment has already been drawn into the master cylinder & is likely now dispersed through the clutch hydraulic system.

Hopefully if the weather is fine tomorrow I'll be able to flush some fluid through the lines & see what, if any, contamination is actually present in the master & slave cylinders.

306maxi said:

Hmmm mine is the same. I would say mine is worse.

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Many thanks for checking that out Maxi . If anyone else can post a picture, I'd really appreciate it.

Andy Monty said:

sorry should have made that a bit clearer i ment that the fluid is shot rather than it been something like a deteriorating seal leaving the film behind

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Thanks for clarifying that. I'd agree completely - there's no sign in the sediment of any kind of seal failure or internal corrosion & I'm hopeful that I'll find the same to be true when I flush the lines.

RobW said:

Probably just debris / contamination from the system, if the clutch works I wouldn't stress about it

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If you're the first owner & you're planning on chopping the car in before the end of its warranty, then I'd agree about not stressing unduly. LHD owners can similarly relax - their cars have a cable operated clutch & can't be affected by this. It's never going to be a safety issue, but I'd like to reserve judgment on the longer term implications until I've seen what comes through the lines when I flush it - from what I've seen so far on my cars, and Maxi's picture, I think it's too early to trivialise this as insignificant.

You do now realise im going to have to go and take a look at my sisters 500 in the cold :bang:


(least on the GP its clutch is off the brake fluid bottle which i hope is better sealed)

I bring better news today .

I've flushed the clutch hydraulic system on both cars & there's no sign whatsoever of any further sediment or contamination in the removed fluid.

Even better, it's possible to do the job without removing the battery .

On the 500, it helps considerably to unbolt the airbox & move it aside - but be careful not to damage the rather fragile breather pipe attachment moulded into the rear (no need to remove the pipe). This isn't really necessary on the Panda as there's a bit more clearance between the airbox & front grille.

Getting a small camera in the space below the battery tray helped me work out what to do. The nipple is separate from the bleed screw and does not rotate with it - you'll need a 4mm allen key to loosen the screw. It's necessary to work blind, but if you first study the photos I've attached (just click to enlarge) & then put your hand in there going underneath the top hose, you should be able to feel what I mean.

I did both cars easily with half a litre of fluid, including washing out the reservoirs thoroughly, so a 250ml bottle is sufficient if you're just doing one.

On the basis of what I've found today, I'd say this:

306maxi said:

I'm not too bothered.

I think I might get it flushed and new fluid through it at the next service though.

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is an entirely appropriate and measured response.

My current recommendation is to ensure that the clutch fluid is replaced at the same time as the routine brake fluid changes; ie every 2 years.