Noise from Clutch master cylinder

Technical Area Engine & Transmission
#1
  1. My model of MX-5 is: MK2
  2. I’m based near: Wimborne
  3. I’m looking for technical help or recommendations on: _clutch master cylinder/clutch pedal assy.

having checked out the various topics on this subject I am seeking further information on what I believe to be perhaps a dry seal within the master clutch cylinder. This dry, low pitched squeak noise shows itself when the car interior is warm and pressure is on the clutch pedal approx. half way down the stroke. Lifting slightly and pressing again on the clutch pedal makes it more noticeable. Its an annoying noise when in reality there should be none.
I have replaced the main bolt bushes along with the bush in the push-rod fork to clutch master cylinder. All parts have been lubed with white lithium grease liberally. Pressing the clutch pedal by hand the sound was just audible as I watched the plunger pushing on the sliding part within the bore of the master clutch cylinder about half way down, and could be made constant by taking off and applying pressure.
Anyone else experienced this and if so what was done to remove it? My thoughts are turning to replacing the seals within the master clutch cylinder. Over to you guys

#2

I’ve had this on a couple of cars in the past…

Best solution I’ve ever found: spray everything you can see in WD40.

Sounds crude, works a treat… In all cases I’ve had of this, it was nothing more than a dry pivot joint or bit of squeaky rubber, WD40 does a far better job of getting into the nooks and crannies than manually applying lithium grease ever would.

Also, the internals of the cylinders are actually soaked/immersed in brake fluid, therefore there’s nothing internally that can go dry really, if the seals need replacing it’s because they’ve failed and it’s either leaking or you’ll lose your clutch completely…

Give it a good dousing of WD40 or similar and see how you get on, it won’t harm anything so don’t be afraid to go mad, but don’t for example squirt it with the precion tube directly into the master cylinder assembly :+1:

1 Like
#3

Clutch slave cylinder do have a tendency to squeak, the pivot point to the lever dries out over time.

#4

Hi ChrisMK3 and MickAP
many thanks for your replies.
There are no leaks to be seen nor loss of fluid and the clutch operates in the correct sense with a good gear selection.

I sprayed the lithium grease via the small red tube such that it got to the pivot points and the fork pivot mounts hoping for a quiet return to a silenced master cylinder, no go. Hence my request for advise and I thank you both for that.

I am a great believer with the WD 40, but have to admit, even though it is in my shed I by passed it for the sprayed white lithium. I understand that the seals within the cylinder are lubed with clutch fluid, but the noise just appears to be rubber against a dry spot within the bore. Can the push rod become offset on depressing the pedal such that, its angled slightly offering a weighted spot to the piston within the bore, therby causing the seal to be compressed more on one side?
Tomorrow I shall liberally spray WD40 and perhaps induce some clutch fluid into the bore with the clutch pedal depressed and see what gives.
Meantime many thanks for taking the time to reply and I’ll let you know my results later.

#5

I wouldn’t use wd40 as it will damage the m/c piston seal over time.
Use a silicone spray or one that’s safe for rubber components.
I’m not sure if there’s a cdv in the system somewhere, if there is it could be the culprit.

1 Like
#6

Hi overdrive
had me wondering just what a cdv was, had to google it. Based on what it says there is not one in the MX 5 system. Apparently this valve was used by BMW to prevent stalling of the engine such was the fierceness of the clutch. This put some buyers off buying BMW’s apparently because they kept stalling, hence the fitting of the valve dampened the action of engine engagement.
Many thanks for taking the time to reply.

#7

They’re used in many other cars as well, to compensate for poor driving technique :rofl:

#8

My update on what I found was the squeak from the clutch master cyl. After taking out the bushings on the clutch pedal assy. and re greasing new ones for the second time and still having the squeak afterwards I looked at what else? I could have kicked myself with what I noticed, and wondered just why on earth I did not do this first off, perhaps I did but it did not register. Removing the cap from the clutch fluid reservoir I noticed black deposits floating within and a lot of black debris settled at the bottom, seal deterioration! Why oh why did I not notice this before I ended up as a contortionist along with a back ache! Cutting a long story short a quick order to “Autolinkuk” and I had the new replacement seals the following morning, excellent service from these guys. Removing the master cylinder was relatively easy as was replacing the seals, though the cir-clip was a p-g to snap in. On inspection of the removed seals the problem was noticeable, worn with a noticeable lack of rigidity about them. With the bore cleaned and inspected, no flat spots or ridges or scratches seen the new seals where coated with fluid and fitted. Installed in the car with clutch bled, lo and behold noise gone. Out for a spin, clutch noticeably positive and more to the point, no noise. Thank G-D for that.
Thank you all for taking the time to suggest remedial actions all.
Mike

4 Likes
#9

So pleased you got to the bottom of it, there’s a lot to be said for the simpler cars .