ChrisL
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| posted on 16/11/12 at 06:35 PM |
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MX 5 Clutch hydraulics
Ok so not a kit problem but one that's vexing me at the moment.
Driving home a couple of day ago went to change gear and the clutch pedal is immediately soft. So either the master or slave seals have gone. Opened
the bleed valve (with pipe etc) and pumped the pedal, almost no fluid come out, so I figure it must be the master that has failed an order a new seal
kit. Replaced the seals and yes the old one was shot, great I think problem sorted, however on trying to bleed I once again get almost no fluid out.
Even pumping vigorously (the clutch pedal!) serves only to move an air bubble along the bleed pipe, a bit!
My thinking that no fluid when bleeding means a problem with the master cylinder as if there was a leak or the slave was shot would mean a drop in the
reservoir level, but it stays the same. The master is back together properly so I'm at a loss as to what the hell is going on, at this rate
I'm going to end up paying someone to fix it :-0
Any ideas???
TIA
Chris
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theconrodkid
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| posted on 16/11/12 at 07:00 PM |
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it,s normally the slave that gives up,if that looks ok,try to borrow a pressure bleeder or slacken the pipe just a gnats at the master and get someone
to pump the pedal
who cares who wins
pass the pork pies
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avagolen
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| posted on 16/11/12 at 07:18 PM |
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I had a similar problem years ago on a hyd clutch - Chrysler 2.0 - similar to the old Avenger.
Bleed it, one application later, air in the system. Bit the bullet and changed the slave cylinder
and fixed it. ( bit costly then )
There were no signs of oil leaking, but it was sucking air. Took a lot of fluid before I fianlly worked it out...
The Answer for everything, but never the last word....
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BigLee
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| posted on 16/11/12 at 07:25 PM |
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Like conrod said, it's normally the slave that goes, not the master. Although the distance from pedal to clutch is short, there is a reasonable
length of pipe as the pipe coils round a few times before the slave. Could be a few air pockets within that. The only other thing I've
experienced, is if the master doesn't fully come back to rest it doesn't refill from the reservoir, so if you do it quickly, it's
just moving the same column of fluid within the system if that makes sense. Pressure bleeding is the easier way. I did mine with an oil can and a
length of silicone. Both slave and master are cheap enough if it goes totally wrong.
Lee
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ChrisL
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| posted on 16/11/12 at 07:26 PM |
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Cheers guys, I guess £50 for a slave it'll be worth trying, just don't know why I'm not getting any fluid. Oh well will report
progress!
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theconrodkid
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| posted on 16/11/12 at 08:00 PM |
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£50 
http://www.ebay.co.uk/sch/i.html?_trksid=p5197.m570.l1313&_nkw=+mx5+slave+cylinder&_sacat=0&_from=R40
who cares who wins
pass the pork pies
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rusty nuts
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| posted on 16/11/12 at 08:03 PM |
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Did you "prime" the master cylinder before refitting it by putting fluid into the inlet and operating the pushrod while holding a finger
over the outlet and releasing the pushrod until you have fluid coming out of the outlet? Another way to bleed it is to apply a vacuum to the bleed
nipple
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ChrisL
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| posted on 17/11/12 at 07:13 AM |
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Unfortunately needs must, have to get the car working for monday, so £50 it is!
Didn't realise I had to prime it, will try that before getting the slave
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skov
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| posted on 17/11/12 at 08:12 AM |
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You don't have to prime it, but it does help.
Bleeding brakes/clutches from empty can be a total b!tch, and often requires several hours of perseverence before you reach that magical moment when
the pedal firms up and starts pumping fluid properly!
Strangely getting p!ssed off and leaving in it overnight seems to work wonders.
Many times I've spent hours and got nowhere, then tried again the next day and it's taken minutes!
My current favourite method is to back-bleed with a syringe.
Basically you fill a big syringe with fluid and connect it to the slave nipple with a short length of hose.
Open the nipple slightly, then force fluid (and any trapped air) backwards through the system with the syringe.
repeat a couple of times till the master resovoir is full, then bleed using the normal method to get out any remaining air.
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adithorp
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| posted on 17/11/12 at 08:41 AM |
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As said by others it's probably a slave fault but if it is that would usually leak fluid at the slave cylinder.
quote:
Originally posted by ChrisL
...Opened the bleed valve (with pipe etc) and pumped the pedal, almost no fluid come out, ...
Any ideas???
Chris
That's not the best method and clutch hydralics in particular won't respond to it.
You need two people; Open the bleed nipple, push the pedal down, close the bleeder (pedal still depressed), release the pedal, open bleed... repeat
untill no bubbles. It helps if you manually (either with the push rod or a thin screw driver) push the slave cylinder piston fully in when doing
this.
If that doesn't work try pumping the pedal fast then holding down and open the bleeder (beware of the squirt) and repeat. Also you can try
opening the bleeder and manually pushing the slave piston fully in, then close the bleeder.
Purging the master cylinder before fitting is the correct way but I suspect few of us do as it's so messy. Leaving the nipple open untill fluid
gravity feeds through can help. Pressure and vacuum bleeding are usefull but don't always work.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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jabs
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| posted on 17/11/12 at 09:16 AM |
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£50 ??
Normally £25 from decent motor factors
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rdodger
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| posted on 17/11/12 at 10:24 AM |
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£15.40
http://www.mx5parts.co.uk/clutch-slave-cylinder-aftermarket-mk1225-p-252.html
Their stuff normally arrives next day.
[Edited on 17/11/12 by rdodger]
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ChrisL
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| posted on 17/11/12 at 11:12 AM |
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Cheers for all the advice, so points go to everyone that said "It's the slave cylinder" you are correct!
I guess I had a damaged seal in the master but it wasn't making any difference, well at least that's changed two.
One of the downsides about having kids is the wife is no longer available to 'push the pedal... hold it...let go...etc' So had to
improvise with a big bit of wood. Hard work though, up down every couple of min's.
Next job replace two brake lines, what a fun weekend, hopefully get it done today and go for a blat tomorrow, in the kit.
Thanks again, as always spot on!
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