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Loss of clutch (R400D) -- second opinion, please - FIXED!

John Vine

By John Vine
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John Vine

John Vine

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Suffered a 95% loss of clutch action today.

Symptoms:

  • Light, spongy pedal
  • Impossible to select any gear at rest
  • Very limited clutch action -- if I press the clutch with the engine under load, the revs rise slightly (equivalent to a slipping clutch, for example)
  • Clutchless changes de rigueur once on the move
  • If I have to stop (at, say, traffic lights), the only way to proceed is to switch off, select first, then hit the big red button, whereupon the car lurches forward and takes off (not wonderful for the starter motor, I imagine)

Observations:

  • Clutch m/c fluid level is normal
  • A few streaks of fluid spattered on the scuttle shelf, suggesting some had been ejected
  • M/c fluid level does not change when the clutch pedal is pressed
  • Clutch operating mechanism in pedal box is OK
  • The piston rod entering the m/c has a black "rubbery" coating (odd, this?) -- but not wet or covered in clutch fluid. (Rubbed off the boot?)
  • There's no fluid or apparent leak underneath the m/c rubber boot

My initial diagnosis is that the m/c seals are leaking.  If I'm correct, what are my options?  Can I get a seal refurb kit, or is it better to stump up for a new m/c?

As the car and I are both currently in SW France (en route to the Pau GP Historique), it would be good to know what car the m/c comes from.  But if it's something our gallic friends won't recognize, I'll need to ask Tony in Parts to send out the necessary bits for me to fit.

JV

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Pendennis

Pendennis

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Could be one of many reasons John, a failed clutch cover would give you these symptoms but I would start with bleeding the system first. Doesn't sound like you have a leak of any sort due to lack of evidence. Oh btw I be surprised if you would notice any level drop in the fluid reservoir when pushing the pedal sorry

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John Vine

John Vine

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Thanks for that, Pendennis. 

So, my first job tomorrow will be to bleed the clutch.  Out of interest, if there's air in there, where would it have come from?  And does the fact that the m/c fluid level stays the same suggest leaking m/c seals?

JV

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Pendennis

Pendennis

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Doubt you have air, maybe moisture contamination which happens over time.

No John, bear in mind it would be very difficult to notice the reservoir fluid level drop on a perfectly operating master cylinder. I am not saying your seals are not the problem but you would not see the level drop whether they have failed or not. I hope it's not a broken clutch cover finger but reading your initial post that's what I put my money on, hope I am wrong though. All the best.

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John Vine

John Vine

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An update...

While my wife operated the clutch, I listened to the master cylinder.  I could hear what sounded like a spring compressing or scraping.  After a few pedal strokes, my wife reported that the pedal had become firmer under her foot. But after a while, this seemed to dissipate.  

I then tried to bleed the clutch, but with mixed success as I didn't have a suitable length of clear plastic hose.  I may have got a little air out (the fluid level in the reservoir dropped by about 1cm, but may simply have been dribbling out of the bleed nipple).  I'll have another go once I get some decent hose and a bottle of DOT 4.

A question about diaphragm fingers....

How many of these would have break before the clutch action was seriously impaired? One, two, lots? 

JV

 

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Pendennis

Pendennis

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Only one John, but flush the fluid through is first step, If it bleeds okay that suggests the master cylinder is okay. However, if your wife is correct and the pedal goes firmer, it could be air, lots of moisture or faulty cylinder. Hope it works out okay for you.

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John Vine

John Vine

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Only one

Uh oh, I hadn't realized that.  But I'm puzzled how just the one could have such an effect, given that my clutch cover has 15.  What exactly happens, then, when a finger fractures?  I can imagine something jamming the mechanism, or even rattling about, but I can't see (at the moment) how it would prevent the CRB operating on the remaining 14?  (You can see I'm clutching at straws here!)

Had another peek at the m/c cylinder today.  The fluid is a dirty black colour (as opposed to a golden honey hue when new), and there are tiny black bits mixed in.  Is this normal, or is it evidence of a seal problem?  The car is now seven years old and has done 35K miles, so the fluid should have been changed at least three times by now (it's been regularly serviced by either Millwood or CC). Also, there is a small weep of fluid under the rubber boot (not visible with the boot in place) and this seems to have caused the boot rubber to degrade and leave a black smear on the piston rod.

Another thought occurs to me... could the slave cylinder be at fault?  Is this a troublesome part or is it bullet-proof?

And another thought.... can the m/c seals be damaged if the length of pedal travel is too great?  I've got a pedal stop fitted, but I'm wondering if it might be set up incorrectly.

Anyway, I've taken a punt on the m/c being at fault and ordered a new one from the UK on the basis that that is at least a repair I can do here in situ.  I've now got some DOT 4 and PVC tubing, so can do a proper bleeding job.   If that doesn't fix it, then I plan to get in touch with Marcassus Sport near Toulouse (about 50 miles from here).  Fortunately, I have alternative transport as my wife drove down separately in our tintop.

Thanks for all your help and advice to date.

JV

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colindavies56

colindavies56

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The fluid your describing should be binned,lost its viscocity.

And yes,if the peddle travels too far,the piston seals will pop out of the m/c.

But that should have happened before 35k.

You could pull the cover boot back while wife presses peddle and see if you could see part if the seals.

And no,slaves are not bullet proof.

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Pendennis

Pendennis

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I had one finger break and lost any clutch actuation, admittedly sometimes it grabbed. But I suspect the slave must travel off centre further and become inoperative. Also if the slave fails they generally leak so if there's no fluid coming from the bell housing/engine joint I suspect your okay. It does sound like your fluid is in a bad way, also seems like your m/c isn't in good shape either, fingers crossed that's the problem 

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John Vine

John Vine

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An update....

I'm delighted to report that my initial diagnosis has proved correct and that a new m/c has restored the clutch to normal.

However, this wasn't quite the smooth ride I was hoping for.  I'd ordered a m/c from Merlin Motorsport, plus a seal refurb kit.  (Although CC stock the m/c, they don't do the seal kit.)

Tracking my order, it appeared that the Merlin parcel was stuck in customs at Charles de Gaulle (Roissy) airport.  Following some expert web browsing by my wife, I ordered a second m/c from Oreca Stores in Provence.  This arrived at my local parcel collection point this morning.

I fitted this new m/c this afternoon (along with crisp, clean DOT 4 fluid), but was mightily alarmed that I still couldn't select gears on tickover when I dipped the clutch. At first, I feared that maybe the problem was nothing to do with the m/c, but rather the slave or the clutch cover.  I bled the m/c twice more to be sure there was no air in there, but to no avail.  However, by adjusting the m/c piston rod (extending it by about 1.5cm), I was able to produce normal clutch action.  There's now minimal rod thread within the pedal clevis, so a longer term solution might be either to get a longer rod or to move the whole pedal assembly to the rearmost position.  

The puzzling thing is this.  I ordered what seemed like a bog-standard Girling 5/8"-bore clutch m/c from both suppliers.  The external dimensions were identical to the original, and the piston rod was the same length.  Yet the Oreca item required an extra 1.5cm between pedal clevis and m/c body to work properly.

Are there, in fact, differences between seemingly identical Girling m/cs?  For example, do they have different piston designs?  (I couldn't match up part numbers so couldn't be sure I was truly buying like for like.) 

JV

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  • 2 weeks later...
DJ.

DJ.

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I'm in the process of replacing the master cylinder on my Sigma car and the one that came off was 0.7  inch bore. 5/8 is 0.625, so that would need greater travel to displace the same fluid as the 0.7 one.

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John Vine

John Vine

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Yes, that makes sense.  I replaced my m/c like for like.  Tony in Parts confirmed it should be 5/8" bore and that was certainly what was fitted originally.

Could it be just that the Sigma cars are different?  What year is your car?

Can someone with a new-ish R400D (say 2012 on) tell me what clutch m/c bore size they have?

JV

 

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John Vine

John Vine

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Another update....

I've just refurbed the old m/c.  Both seals were intact but the piston seal had seen better days -- the edges were all rounded and by no means smooth.

Any news from R400D owners re their clutch m/c bore size? 

JV

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  • 3 weeks later...
Alan Reeves

Alan Reeves

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john are you back in the Uk and what was the update. i have just ordered a new repair  kit as I am going to Italy and been watching your saga...I think the CSR is different though?

 

When I built the 175 Dura there was a clutch issue and I had to take it all out as fluid was being emptied into the bell housing...ijn fact i drilled a hole in the bottom of the bell housing for future issue...and put a little plastic bung in

alan

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John Vine

John Vine

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Hi Alan,

Yes, I'm still in France (SM25T's link gives the current situation).  The car is due to arrive at Marcassus Sport near Toulouse this morning.  I've been in touch with Marcassus and they think they'll be able to do something for me.  Engine out job, anyway.  I'll be going over there later to discuss options etc.  Fortunately, our tintop is here so at least I have back-up wheels.  See my later thread for developments.

Pau was as brilliant as ever, although the older classic event was less well supported this year.  And the R300 Challenge was moved to the Grand Prix Moderne (the previous w/e).  Enjoy Italy.  Hope the CSR proves reliable!

JV

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