Solid clutch pedal

I posted this in my build log, but will repost to see if I get any responses

Finally got round to bleeding out the clutch line this week. Once we finished, the clutch pedal is solid.

To try and diagnose, I took the slave out and it appears to be moving fine. Pushed all the way in and then my friend pushed on the clutch and we have movement. So it appears that the problem may be down to inside the gearbox?

So I guess a few options and need some advice. I bought the slave, as it was the Audi cylinder that the new RF team used on their 01E boxes, as it has a push on adaptor that they sent to me. So the travel should be OK? Doing some very rough measurements the travel should be ok as I could feel the clutch fork and by finger measurement it should have enough travel.

As the car has been sitting there so long, could things be seized inside the box? If so, what is the best way to diagnose this and potentially resolve?
 

Ian Anderson

Lifetime Supporter
Hi Brett
On my car that was in build a number of years before I got it the clutch had welded itself to the flywheel so would not disengage, the other side against the clutch had broken free on pressing the clutch.

SimI would presume if both sided had rusted to the clutch plate you could get a solid pedal.

Probably be a box out job I'm afraid, certainly was with mine, parts prised apart with paint scrapers, light sand off and re assembly.

Ian
 

Mike Pass

Supporter
I would have thought it unlikely to be gearbox related. If the slave is moving OK then it seems that something is preventing the slave cylinder from pushing the release bearing in to actuate the clutch. The clutch fork may be stuck or jamming against something. Or the clutch assembly may be stuck together preventing the plates from separating. The plates may be stuck by rust. If there is a slight springiness when you press on the clutch I would suspect the stuck by rust as the spring fingers on the clutch cover are slightly bendy. If it is rock solid I would suspect something jamming the clutch fork or release bearing carrier. If the plates are so stuck by rust corrosion and it is so bad as to prevent movement then the usual trick of rocking the car in a high gear with the clutch pressed is not going to work. You can check the gearbox is OK by lifting the rear wheels off the ground and spinning the engine over on the starter in all the gears.mtake the plugs out to give the starter an easier time. If you engine will run the use that to check that the wheels spin OK in each gear. Make sure the car is securely held on axle stands if you do this check. If the box is OK then a strip down separating the engine and box to check what is going on with the clutch.
Cheers
Mike
 

Mike Pass

Supporter
I have just had a quick look at your build log at the part where you have your new driven plate and the assembly of the gearbox to the engine. On the pic of the clutch cover installed on the flywheel it looks to me that the metal boss at the centre of the driven plate is too big and you can see this just below the clutch fingers. If the clutch fingers are prevented from being pushed in by the driven plate boss then the clutch will not open and you will have a solid pedal as you are trying to compress the metal boss of the driven plate. I guess you are going to have to remove the box and strip the clutch and modify the driven plate boss to allow the clutch fingers to move and the clutch to operate normally. I am not sure which clutch bits you have whether Renault, Audi or a mixture. When I spoke to Helix about the Renault clutch I had on my car initially. They told me that the max torque the Renault clutch would take even with their upgraded parts was 280ft.lbs. which was why my clutch was always slipping once it was even slightly worn. I replaced it with one on Mick Sollis's AP Racing ones which are rated at 340 ft.lbs. and it has never slipped since even with regular abuse.
Cheers
Mike
 
Hi Brett,
Did you check that the piston in the slave cylinder is returning. I had an issue that the piston would come out, but not retract giving a solid pedal & no movement. I traced it to the non return valve the master cylinder sticking. After this was freed off the system was Ok
Rgds,
Andy
 
Mike, the drive plate should be the correct way round. I guess I will need to check. I will have another go at seeing if there is any spring in the pedal. I really don't want to have to take the gearbox off, as it will mean having to not doing anything on the car until spring, as I have to do that on the drive/garage door open. If I remember when I put it all together, there is enough room and the release bearing should also be able to slide over the drive plate boss.

Andy, the slave does not return, but I am not sure if it is designed this way or not with the Audi cylinder. It feels like there is a spring in it that pushes it out all the time, as if I push in and let go it comes out
 

Mike Pass

Supporter
It is hard to tell from the pic of the assembled clutch (re-attached) as it is quite low resolution so even when I zoom in there is not enough detail to see clearly. From what I can see it looks like there is not enough clearance for the fingers on the clutch cover around the boss of the driven plate. If you have a better resolution pic you may be able to see it better than I can. If these clutch fingers can not move past the driven plate boss they will lockup solid when you try to operate the clutch and give the symptoms you describe. If this is the case then you will have to remove the box and turn down the driven plate boss in a lathe to get the clearance needed. Maybe the supplier of the clutch bits can shed some light on how it is all supposed to work together. Do you have pics of the inside of the bellhousing and clutch release mechanism?
It is a bit of a pain taking the box out - I know as I have done it at least 6 times! You should be able to get it out in under 2 hours. I don't know what weight an Audi box is but I can wrestle the Renault one in and out OK by myself but it is much easier with a beefy helper.
Cheers
Mike
Klaatu barada nikto
 

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Are there any openings large enough to get a small TV camera probe/flexi into the area for a look see [ only needs a 20mm hole], I had a quick look at your clutch plates and the pic mike has posted last night and there is a possibility the situation he describes exists.
 
Sadly the photos were taken with an older camera that was low res, so below is the best I can do. Regarding the whole setup, it was mismash of bits together in the days before suppliers started offering 01e/01x adaptor plates and setups. It is a Kennedy adaptor for a 016 and then a Helix plate made afterwards based on the larger input shaft and relation of the splines. KNowing me I've probably done something wrong :huh:

DSC02087 by Brett-GT40, on Flickr

and a picture of the inside with the fork and original release bearing

DSC01516 by Brett-GT40, on Flickr
 
If your still using that release brg & fork there is a possibility that the fork hits the clutch cover before the bearing gets a chance to release the clutch, still a possibility of the clutch fingers hitting the plate hub before release also.
 

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Mike Pass

Supporter
It may be significant when you say that Helix made up the driven plate for the larger input shaft. If the shaft and hence the boss are larger then the hole at the centre of the clutch cover fingers may be too small for the new larger boss. As you have a reasonable thickness of metal on the driven plate boss the maybe a better course of action may be to trim the length of the fingers rather than turning down the boss. This would need to be done accurately to ensure that the new lengths are equal on all fingers.
Setting the throw of the release bearing to match the movement needed by the clutch cover can take a bit of careful measurement and calculation and selection of the master and slave cylinder ratio. I had to use a sleeved down slave cylinder to get the best ratio with minimum pedal push.
Cheers
Mike
 
I'm thinking Jac is right, the clutch fork looks like it would hit the pressure plate and stop. Maybe you need a new carrier for the thrust bearing so it can reach deeper into the pressure plate, Didnt Jim C glue a spacer or similar onto his 01E set up to get reach?.
Easy test to confirm--Get you mate to push on clutch pedal while you try to turn motor, the motor will be locked or make a scraping noise, will scratch the paint off the pressure plate if touching. Then shine a light in the bell and see if you can see a mark on the pressure plate.
 
Last edited:
Hi Brett, check the length of the splined section in the disc, I got bit big time on a stage 4 pressure plate and disc from Kennedy eng, I ended up removing almost 1/4 inch off the length of the back side of the splined section on the clutch disc . Turns out the trans [016 Audi] was trying to push the disc thru the flywheel! trans in and out 7 times!!!!1 and I am a mechanic by trade!! Check also that the audi slave hasn't bottomed on the circlip at the end of the slave at the beginning of the stroke, let me know if this helps.
 
So I took the back off the car last night and to me it looks like the fingers should have enough room around the plate boss

20141211_213644 by Brett-GT40, on Flickr

I haven't had a chance yet to look at the release bearing and measure to see if it is hitting on the inner sleeve as I have put my verniers down in a 'safe place'.

I think I'll give Jim C a PM to see what he did on is release bearing.
 
Brett:
What Neville said happened to me...wrong pushrod on the slave to fork...2 pumps and a solid pedal....the piston hit the internal snap ring in the slave.
There should only be approx. 3/4" (19mm) travel on the release bearing so it is very easy to mis-measure....sorry you had to break the gearbox from the motor...I feel your pain! Not my favorite thing either.
I also have seen some very hard pedals with the wrong master cylinders...but I am assuming you have all that sorted by now.
Cheers and good luck
Phil
 
You need to check the stroke in the slave.
If the fork is to far in the slave will be further out and it has a curclip in the end to stop the piston coming out,when the piston hits this it will go solid.
Putting a longer push rod is not the best option, I used the spacer because it puts the fork back in the correct position as well as the correct shape for the pressure plate used, also the fork needs travel through the correct ark.

Brett in my build thread RF105 post 72 is a pic of the spacer if it is answer to your problem
I machined it out of 4130 ,no heat treating.

Jim
Jim
 

flatchat(Chris)

Supporter
The measurement from the bell bolt up face (of the gearbox) to the thro out bearing when fully home is ~90 mm
The measurement from the clutch(assembled) fingers to the engine block (or where the g'box bolts up to) should be ~85 mm
A 5mm gap is good
If the gap is more than 10mm --a spacer for the TOB is needed or you may try a spacer under the fixed pivot point (where it pivots off the G'box) of the fork.
Lets know what ya find?
 
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