Non returning clutch pedal on track?

I had this at Spa, when i got home i pulled the gearbox out and the clutch was almost shot, so replaced the clutch and the clutch pipe, replaced the clutch pipe with a straight pipe without the diaphragm thing in it.

Not had the problem since

 

yes mine was fine after it cooled down, but happened again when on track, changed the clutch and have done 8 trackdays at least and have not had the problem again.

 

I had this at Combe earlier in the year in my R26, when everything cooled down it was okay. The next time out at Abingdon the brake pedal did the same. I've replaced the fluid (Motul 660) and it was okay until yesterday at Pembray when the clutch pedal went again. Going back to the pits it popped back into position again. All three times it was hot conditions. So I know its not vapour lock and I suspect Ian is right and the clutch is on its way out and/or I'm riding the clutch pedal a bit without realising.

 

Hi Rich
I did start to have a problem at Snetterton last Tuesday, one slower lap and it was all good again, my clutch was changed over the winter so not had that many track days on it.
Must be getting really hot in there, it was 24 degrees at 08.30 the first time i have had any problem since fitting the new clutch.

 

When we do a brake fluid change we bleed the brakes and then bleed the clutch last, therefore hopefully getting rid of all the old fluid

 

No i doesn't automatically change the fluid in the clutch parts, i have RBF660 fluid in mine, so when the clutch was changed the clutch was then filled with the 660, i did 2 Nurbergring trackdays and not a problem but it was hot at Snetterton

 

There's an old thread about this problem (https://rsmegane.com/threads/brake-clutch-bleeding-guide.12079/) where its caused by air/contamination. I think the my problem (and possibly Ian's) is different because the fluid in the clutch lines has been replaced and bled.
Also if it was an air problem wouldn't the pedal gradually come back up as it cooled, whereas my pedal litually popped back up.
I'm thinking maybe the Master Cylinder is getting sticky with the heat, but I've also read that there's some sort of 'in line' valve between the Master and Slave. If this valve is fitted on the R26 and 265's it would be interesting if someone knows how it works and if it could cause this problem?

 

there isn't a damper in the pipe on the R26, it's only on the MK3's, i have already replaced mine, did this over the winter.
Interesting about the master cylinder, it isn't that far away from the turbo so wonder if that is the problem.
My gearbox is being replaced tomorrow, while its out i will drain the fluid from the slave to see what it's like.

My peddle does or did come back on a cool down lap

 

Might be an idea to try a temp heat shield around the Master Cylinder then?

 

I have some fire proof cloth, might shove some of that in the area to see if it makes any difference, doing Bedford on Saturday so will give it a go there.

 

Will do, just had my gearbox replaced today, so need to give it a really good test before the warranty runs out

 

Hope the Gearbox is okay on Saturday Ian and it'll be interesting to see what happens with the Master Cylinder.

 

Drove it very briefly today, all feels good

 

had the same problem with my 250 at Brands after 4 or 5 laps. pedel and bite point just gets lower and lower until its almost impossible to select a gear ! I have flushed the fluid through which was clean. think it could be a failing slave cylinder. am at Bedford with Ian tomorrow so will see how it goes. don't want to be putting a clutch and slave in it as the clutch feels fine otherwise

 

well the clutch seemed to be ok but I didn't get to many laps in as my 250 engine decided to shit itself and blow a hole in the block

 

Never had a single problem with my peddle today, it was cooler today so i think that may be the issue.

 

no was running a hybrid etc. but not excessive power.

 

Just been through all my camera footage and i never really had a full clear lap but most laps were under 2 minutes and had a couple at 1.55 and the best was 1.53.
Was on the SEN circuit that's 2.3 miles long.

 

I had this happen last year at Spa after a few laps, totally ruined the session. Clutch stayed pinned to the floor and then slowly released as the fluid cooled.

Replaced the line with one without the damper (I know this wasn't the issue but their a known weak point) and then had the fluid replaced with Castrol SRF Racing.

Did a full day at Spa a few weeks ago. Similar ambient temperatures (hot). No issues what so ever. That's where i'd start.

 

Can only really do it when the clutch is changed

 

My mate did it without removing the clutch. Worked a treat.