I have a 80k miles 2000 1.8 mk2 my first mx5 with a clutch problem, after about 15-20 mins driving (normal roads) or 10-15min in stop-start traffic, the 1st 1/2 of the clutch pedal travel goes really slack, theres no resistance at all, it still rises back up but the biting point is nearly on the floor and to change gear i have to push it all the way to the floor, i took it to a garage who told me the master and slave cylinders were fine (at least not leaking) and suggested replacing the clutch fluid (which i discovered was a hydrolic clutch, thats how much i know about mx5s!), which he did and later said it was absolutely shocking. Probably not changed since new, he said if it continues i might need a new clutch, now im not really mechanical so i dont have a clue about anything but the simplest workings of a car and im not to keen on having to fork out for a new clutch if it could be something else but i always thought that if the clutch was gone or the clutch plate was wearing i either couldnt change gear or stuggle to change gear (which i still can fine) or the biting point would rise up if worn (its on the floor!). can anyone offer any advice? im in the Bolton area.
looking through some older posts trying to find a similar problem someone mentioned a low biting point on the mx5 was normal but im sure this isnt normal it cant because all i can say is it feels wrong and no pedal should suddenly go so slack for any travel movement on any pedal. i’ve driven a few cars and no cars clutch pedal has ever felt like this.
Just signed in for the first of many visits? I’m sure that you will pop your location in your profile, and the year and model of your MX5 in your sig. This helps enormously when we try to answer questions…
Find Mazda Mender here on the forum, he lives in Wigan and he can really help you. Despite what your garage says the symptoms are classic slave cylinder failure.
If I might be so bold as to correct Geoff’s typo this is classic master cylinder failure.
If the slave fails it can only do so by letting fluid escape past its seals and you will soon run out of clutch fluid; it goes into the boot, then onto your drive. Always worth peeling back the boot if it looks a bit suspect when you’re under there to check for signs of early failure.
If a master fails the fluid can escape past its seals and stay in the reservoir so there’s no external leak and I guess that’s what your guy missed. They can be erratic, possibly the cylinder is scored or corroded and/or the seal soft and swollen due to old or contaminated fluid from what he said. Times past we rebuilt these using a seal kit but now you buy a replacement complete cylinder. There are kits with piston available but the bore is often worn. That may be why it still works just at the bottom of the travel where the bore is better.
I’ve seen a number of '5s with a duff slave with no sign of fluid around the slave boot. I would change it first before embarking on the much more expensive job of changing the master cynlinder.
The one’s I’ve seen, the rubber boot was full of fluid, which hadn’t escaped out to air. If you think about it, it’s not the fluid loss that causes the problem, it’s the piston/seal wear that fails to contain the pressure in the system.
It’s precisely the fluid loss (either externally via the slave or internally back into the reservoir) that causes the problem. Without the fluid there can be no pressure transmitted. If failure is due to the slave it is only after it has leaked so much fluid that the master no longer has enough to pump.
What you describe is the early stage of slave seal failure as I explained in my first post. Fluid starts leaking past the seal and shows in the boot.
At that stage 1) you are lucky so far, change the slave cylinder 2) the slave will still work correctly and there will be no failure of clutch operation until the fluid level drops so far that the master runs out of fluid to pump.
Study this clutch hydraulic system - it is the simpest you’ll find - and you’ll see that for a slave to cause loss of clutch operation there has to be fluid lost past its seals to such an extent that the master no longer has enough to pump. That is then obvious by the low level in the reservoir and dripping from the slave.
This was my day job working for a Lockheed Girling agent many moons ago, selling the parts and fitting them for some customers. The classic mistake was for the piston seal to be put on the wrong way round (think about an old style bike pump with leather washer). I rebuilt most of the units including servo boosters which had a nasty failure mode which allowed them to drain all the fluid into the vacuum side of the system and leave no trace of a leak outside. We sold all parts including truck air and spring brakes.
I hate to disagree with a pro, but the last slave I changed on an MX was on my car, very soft pedal, low bite, no fluid loss underneath or from the master cylinder. New slave fixed it. I’ve seen it on landrovers as well
Hey guys, i checked and theres deffo no leakage anywhere plus it has had the fluid change not 4 days ago and the resevoir is still full. Can slave be knackered in any other way than a leak? and how much roughly for a master change? and just on a side note if anyone knows, is the radio aerial supposed to go all the way into the body? mines still sticks up by about 8" lol just wonderin’.
Yes, so long as they bleed it correctly, and if air is the problem, you have good chance of success. The slave itself won’t make a difference if you’ve not been losing fluid from it. Good luck and let us know
this is classic master cylinder failure.