clutch pedal soft when engine is started

Elan Discussions
1

Hi all, I’ve fitted a new clutch plate and slave cylinder with a Speed bleeder on my +2 and can select all gears (4 speed) when in neutral with the engine off. When the engine is started the clutch pedal goes soft as if it needs bleeding and its impossible to get any gears
This has baffled me, I’ve been trying the push rod adjustment but no luck
Has anybody else had this problem? Thank you in advance John

2

Air in clutch slave cylinder needs bleeding.
Alan

3

Hi Alan, I’ve had the pedal wedged down overnight and it’s nice and firm, bled it a couple of times with a clear tube on the speed bleeder, no bubbles there. started the engine but still unable to select a gear.
John

4

Hi John, with the engine off, and a firm pedal, have you actually observed that the adjustment rod/release arm are moving back and forth when you press the pedal?

Mike

5

Yes Mike that’s working as it should, but the cylinder has free horizontal play in the bell housing although the circlip is in place.
John

6

You need to push the slave cyinder fully forward so it is hard against the retaining circlip when adjusting the lever arm free play to the Lotus recommended 2 mm value. If the arm is moving around 10 to 15 mm but the clutch still not disengaging then something internally is wrong with the clutch or throw out bearing assembly

cheers
Rohan

7

thanks for the replies.
The pedals gone spongey and now have bubbles in the master cylinder fluid, I have a repair kit so another nasty job with the pedal box.

                                    John
8

The clutch changes in feel depending on whether the engine is running or not? Are you sure? Never heard of that before and can’t think of a scenario of how it could happen.

9

No, the problem is I can select any gear but not when the engine is running, I have another job now changing the seals on the clutch master cylinder,

                                      John
10

That simply says the clutch is not disengaging

11

Set the clutch arm to the factory setting. With the engine off get someone to pump the pedal whilst you observe what is going on at the slave cylinder. Then check the same with the engine running, use a ruler or measure of some kind to make sure the push rod is travelling the same amount in both cases. Next observe what is happening in the master cylinder, does the fluid level change in both scenarios, and are there any bubbles being produced in the fluid in either situation.

If all these check out then it looks like an internal problem with the arm or the throw out bearing. Did you just fit a new clutch disc or did you change the the whole assembly, pressure plate, disc and throw out bearing?
Tony

12

Hi Tony, I just replaced the clutch disc, the slave is new and overhauled the MC, but I think the clutch pedal pressure is not very heavy. I’ve bled the slave with the speed bleeder several times with no sign of any bubbles, but
I still think there should’nt be any free play on the slave, surely this must affect the clutch adjustment, perhaps I could add an extra circlip?

Thanks John

13

There is always some free play in the slave mounting in the bell housingof a few mm, some slave cylinders have two grooves so use the grove closest to the bell housing just make sure the slave is pushed full forward when adjusting the lever clearance.

The clutch system is difficult to bleed due to orientation of the bleeder and can need multiple attemps. and is a two person operation unless you fit a speed bleeder to the slave as others have said after getting most of the air out wedging the pedal down with a piece of 2x4 against the seat and leaving it. However you need to be able to get some pressure in the system for this to work.

cheers
Rohan

14

Is the clutch lever pivot pin correctly installed?

15

Is the new slave the same bore size?

16

More trouble now, pumping the pedal there was no pressure because the MC is leaking fluid down into the footwell.
Why has that suddenly happened, the new rebuild kit was fine earlier today.
I hope that I can just only remove the MC, I have a access hole in the peddle box top

                                  Thanks for all your suggestions            John
17

The weeks go by and I still can only select the gears when the engine is not running.
Just to recap: new master and slave cylinders and speedbleeder, the pedal has acceptable pressure but if I pump away at least 20 odd times it will become firmer… I’ve wedged it down overnight several times but no difference, the cylinders are the correct bore size
I fitted a new clutch plate but the rest of the mechanism is original, so it’s back to the same old question ’ why does starting the engine affect the hydrauilics’

I’m afraid now at my age depression is starting to set in regards John

18

Is the action of the engine vacuum acting on the servo a possibility, Try bleeding the system from the servo outlet port or remove it and check it is not full of brake fluid.

19

The first thing that comes to my mind is that the transmission input shaft is not able to spin freely, specfically it is binding at the crankshaft end, which would prevent gear selection with the engine running regardless of whether the clutch was disengaged.

But the whole soft pedal thing is odd. Crankshaft thrust washers having excessive play? It’s baffling.

20

It is not the engine affecting the hydraulics it is the clutch not disengaging at any time. With the engine stopped you can select gears with the clutch not disengaging but with it running you cant that is normal. The question is why is the clutch not disengaging and from your descriptions it appears an issue with fully bleeding the system or adjusting the lever arm or some issue with the setup and reinstallaton of various clutch components when the work was done.

The starting point is how much iss the lever arm moving when the clutch pedal is depressed ?

regards
Rohan

PS Your steadfast refusal to obtain a camera and post photos makes all of this diagnosis much much harder with your various problems