Clutch pedal - its happened again

[TBD 781]

This first happened to me in February this year. I got back to the car and the clutch pedal fell to the floor when I pushed it. It wouldn't come back on itself. After pulling it back by hand and giving it a few pumpings the pedal came back.

My dealer received a service bulletin on the issue. Apparently the hydraulic fluid ecame too hot and boiled, the resulting gas expanding and contracting depending on the temperature. The dealer bled the pipe and installed the heat shield proposed by Lotus in the SB.

All was well until today, when again the pedal fell to the floor. A few puming on the pedal brought it back, so now its "OK", but a bit soft. So, its back to the dealer and it seems the heat shield isn't sufficient.

[ramjet 1,086]

Surely that would have to constitute a recall if enough cars get the problem?

Though I must admit, I can't imagine hydraulic fluid getting hot enough to boil unless the pipe was wrapped around the exhaust.

Something else at play methinks.

[Bibs 11,165]

Car manufacturers deal with problems with service bulletins which can have several levels of severity. Some are recalls with various levels of severity, some are 'fix next time the car is in for work' and others are 'if it's got the problem, this is the fix'. Since this is the first we've heard of in on here with the amount of owners we have we can assume it's fairly rare, although it's happened an appreciable amount as there's an SB for it although I'd imagine it's the 3rd kind so not a recall.

I assume the pipe is already braided as this isn't similar to the 'red hose syndrome' in Esprits, perhaps there's a motorsport hydraulic pipe which is more adept at keeping heat away from the fluid which may benefit more or a re-routing of the pipe?

[TBD 781]

Bibs, there have been a numer of similar issues here on the forum and I'm pretty sure most of the so-called clutch issues are the same origin.

It is actually a fixed hydraulic pipe, no braid or thermal protection in the original. The SB basically covers the pipe with a thermal protection sleeve. Boiling point for brake fluids is between 200 and 250 °C according to Wikipedia

[Bibs 11,165]

There are motorsport fluids with much higher resistance to boiling too, AP do one which is good for 600^oF I recall?

[mdavies 74]

Can anyone say whereabouts this pipe runs and where the heat shield is added? And whether the problem only arises on the S ?

TBD, are you indicating that the problem happened after the engine was hot, you left it for while to heat soak, then returned before it had a chance to cool? Or a long time after? Was everything cold by the time you found the problem but the gas generated was still present?

The worst circumstances might be e.g. following fast running on a motorway, slowing normally for very slow traffic - no soak yet, slow queuing in that traffic whilst still moving but heat soak happening, then queue stops, brake ......oops!

Edited May 21, 2012 by mdavies

[TBD 781]

The car was cold when I got in this morning, so it would seem that the gas was still there. I didn't feel a difference when the car is hot - everything is normal. You can see the pipe on deroure.com.

Update: Lotus just told my dealer the main clutch pedal cylinder needs to be replaced. They said they have had a few cars in UK with the same problem, the cylinder drillings are skewed or blocked so the fluid doesn't refill properly. Seems to make sense.

Ah yes, the woes of exclusivity.

Edited May 21, 2012 by TBD

[Justin182 11]

I've managed to boil my fluid aswell before. No idea how but the brakes and clutch/gearbox became completely inoperable.

My pedal didnt fall to the floor though

[Bibs 11,165]

They're completely separate systems, weird for both to fail...

[mdavies 74]

I've managed to boil my fluid as well before. No idea how but the brakes and clutch/gearbox became completely inoperable.

My pedal didn't fall to the floor though

Knowing something about the circumstances would be more than a little interesting!

[Justin182 11]

They're completely separate systems, weird for both to fail...

Are you sure about that? I was under the impression they ran off the same system.

[Trevsked 769]

There are motorsport fluids with much higher resistance to boiling too, AP do one which is good for 600^oF I recall?

On reccomendation I tried the Halfords Racing Brake fluid in the VX220 as I was suffering with the fluid boiling on track. Changed and have done one track day at Bedford so far with no fade/boiling so it gets the thumbs up from me.

Trevor.

[TBD 781]

If it was the same system, it would be an automotive first (an a bad idea!)

Actually, there is one point where they both do come together: they share the same brake fluid reservoir under the front hood. So if this runs dry you would have an impact on both.

[Bibs 11,165]

I stand (sit) corrected, never knew that but it makes sense. I assume there's no way boiled and air filled fluid from the braking circuit can make it into the clutch pipe?

[TBD 781]

I would hope not. Since the fluid is notcirculated through the system I would expect boiling to cease somewhere on the way between the hotspot and the reservoir. But a very low level could impact both brakes and clutch.

[Justin182 11]

Yeah thats right. I think the brake fluid had boiled, which somehow is linked hydraulically to the clutch, and they both stopped working.

The clutch went first

[Squidward 3]

Dot 4 brake fluid boils at 250-300 degrees celcius, so I'd say while it's not impossible, it's highly improbable.

[Justin182 11]

I'm only telling you what my dealer told me.

[mdavies 74]

Could there be some effect that after the fluid has "boiled" or whatever, highly expanded anyway, in the brake lines, on cooling it contracts and sucks back sufficient from the combined reservoir to affect the clutch? For that to happen the hot fluid would have to overflow from the reservoir I suppose - should be obvious.

It all sounds very mysterious to me, and I don't really see that as likely. More information needed! Justin, I can appreciate you might not want to give much detail about circumstances - but some?

If this is something that could possibly affect any of us - likely I guess in fairly "heavy use" - I, for one, would like to get to the bottom of it.

Edited May 24, 2012 by mdavies

[TBD 781]

OK; I finally had the main cylinder of the clutch pedal changes on Thursday. Hopefully it will stay fixed now, though the service specialist couldn't see anything in the cylinder that might be awry. Lotus had stated, that they had a few cars with a blocked bore into the cylinder, so that the fluid wouldn't flow back.

We'll see. Right now I've just got the problems with the shift cables again (but that is another thread).

[Justin182 11]

Could there be some effect that after the fluid has "boiled" or whatever, highly expanded anyway, in the brake lines, on cooling it contracts and sucks back sufficient from the combined reservoir to affect the clutch? For that to happen the hot fluid would have to overflow from the reservoir I suppose - should be obvious.

It all sounds very mysterious to me, and I don't really see that as likely. More information needed! Justin, I can appreciate you might not want to give much detail about circumstances - but some?

If this is something that could possibly affect any of us - likely I guess in fairly "heavy use" - I, for one, would like to get to the bottom of it.

What exactly do you want to know?

[mdavies 74]

Hi Justin, sorry about slow response but I’ve been off line.

Looking back over the thread, the issue seems a) potentially serious, b) still rather mysterious. It could be important to know how likely it is to happen in say “ordinary for a Lotus” road driving, as opposed to “X!X!X!” driving! In my experience, particularly on tracks, that is most different for the extra braking and the much longer periods of a really hot engine.

I’m wondering about the circumstances when you found your problem. Were brake and engine temperatures likely to be typical, or higher? For how long? Did your “brakes and clutch/gearbox became completely inoperable“ when you were actually driving, or afterwards. Things still hot or had they cooled down?

Quite apart from tracking, as probably one of the more “press on” drivers, I’m thinking of Alpine descents etc. (Might get to try one before long - not just curiosity!) Thanks.

[ramjet 1,086]

I would like to see this hydraulic circuit diagram. I doubt, under our regulations over here, that a manufacturer would be able to use the one reservoir for both systems. A clutch system failure could potentially leave you with no brakes to stop your car.

I may well be wrong, but I just can't see it. Does someone have a circuit diagram they can post up?

[TBD 781]

Its definitively one reservoir, but they have separate hoses from there. You would get a red light in the dash way before it gets critical. I haven't checked, but I believe its a common design.

[910Esprit 531]

Its not unusual for modern cars to share a reservoir. I was working on a Micra recently and it uses that arrangement. The actual clutch master cylinder is a nasty tiny plastic thing that simply twists into the bulkhead - give me 'classic' mechanicals anyday....