Strange Clutch Problems

[dazzvazz]

Hi All

I was driving home one day and whilst pushing in the clutch the pedal seemed to suddenly lose pressure, then when changing out I was stuck in neutral. I pulled over and after a little while it started working again. My friend thought it must have been an air bubble and I let it be for now.

Literally the next day it happened again. This time it didn't fix itself. The fluid was low, so I topped it up and bleed the system (we were on a very quiet and flat street). After all our attempts we couldn't get any pressure in the clutch. I know when these cars get to this age the master or the slave tend to go, so I started it in gear and drove it home. I ordered a new non genuine master cylinder, non genuine slave cylinder, and a stainless steel braided clutch line which goes direct from master to slave (all parts are from MX-5 Plus so they are good quality parts).

Just today I installed all of the parts, and with my friend we started to bleed the system. It was going well. I was feeling the pressure build in the clutch (amongst a feeling of relief), but then when I was halfway slowly pushing the clutch in it tighten slightly and made a mechanical clunking sound while giving way completely to the floor. From here on now we having had any success in getting the pressure back despite brake fluid bleeding successfully from the nipple.

We suspect it's the clutch fork. One thing I notice when fitting the slave I could move the clutch lever (what the slave piston moves) with my finger.

The question is... Is this something other than the hydraulics (like the clutch fork)?

Thanks!

Dale

[dazzvazz]

From here on now we having had any success in getting the pressure back despite brake fluid bleeding successfully from the nipple.

Haven't***

A few things I forgot to mention... We visually confirmed the slave piston moving the back and forth.

[dazzvazz]

Anyone?

[93_Clubman]

We visually confirmed the slave piston moving the back and forth.

Well if throw of the slave piston is within specified range, & the clutch hydraulic system is holding pressure when it encounters resistence, then this suggests the issue is forward of the slave piston in the bellhousing. However, also worth confirming that your clutch pedal is correctly setup & adjusted as per specs in the workshop manual.

[dazzvazz]

[/youtu]Here is a video of the slave operation. Note that the last time I was incrementally pushing the clutch and managed six increments which the slave responded to each increment.

[wozzah1975]

If all the hyd side of things is working, then I would suggest the problem is further it. Gearbox out for clutch inspection......

Cheers
Woz

[dazzvazz]

Cheers!

As I feared, dropping the box isn't something I want to do...

Anything else I can do while dropping the box? Other consumables that are worth changing while it's dropped?

[Skyntara]

HD Clutch, Lightened Flywheel and all oil seals for engine and gearbox...

At least it'll be worth your while

[Mr Morlock]

I would not be considering a lightened flywheel- some people would avoid buying a car with a lightened flywheel. You did not mention any other info about the car- like model KM's etc. If it is just used as an ordinary sports car then a clutch kit - use the OEM brand Exedy and a standard clutch will do the trick for many further km's. I would guess the pressure plate fingers have collapsed. Standard practise is to reface the flyweel.

[dazzvazz]

One of the springs broke free from the clutch plate and jammed the pressure plate. Luckily I had a spare Exedy Stage 1 clutch kit. It has now been fitted, flywheel has been machined, and the spigot bearing has been changed. I didn't get anything else done as they had it together by the time I contacted them...

Unfortunately, they didn't adjust the clutch pedal. The friction point was like a few mm from the pedals default position.

I just did it myself, but I am not sure if it's 100% correct. While the engine is running and the clutch pedal is fully depressed the engine revs don't change (which is good). I am not sure how to tell if the clutch is fully engaged.

Can anyone confirm if this theory is correct? As you increase the free-play the friction point moves closer to the floor, as you decrease the free-play the friction point moves away from the floor.

Is there any problems with having the friction point too close to the floor other than the clutch not disengaging?

I would do the adjustment to standard specifications, but they don't seem to apply to a clutch that isn't similar to standard. The friction point was way too far out within the standard tolerances.

Thank you for your responses.

[Mr Morlock]

clutch free play on the pedal ie under dash is probably the same adj regardless of clutch set up. The way to check engagement is merely select a gear - put the hand brake on and then lift the clutch and you will see when it takes up. Why not just return the car to the fitter and ask them to do it for you- that is part of the job. Probably take them 5 mins. PS repair manual should have spec. PS as a logic if there is no free play the clutch will start to disengage immediately you apply pressure.

[dazzvazz]

I really should take it back. At high revs while the clutch is disengaged it makes a rather ominous noise and vibration. I noticed it first when changing gears at 5,000RPM or higher. When I climb the revs then disengage the clutch to change gears it makes the noise. Then I pulled over and tried it in neutral, climbed the revs and engaged/disengaged the clutch. Whenever the clutch is disengaged it makes the noise (sounds like a real strong vibration).

I will call them up and see what they say...