Clutch master cylinder seal kit potential...

[biffa75]

Been using my spare time again during my night shifts and trying to find possible solutions to issues that I myself and possibly others face.

So.. clutch master cylinder,
I know there is the metal tazu master cylinder but reviews are mixed with no clear answer as to whether it's the way to go or not..

I understand the luk master cylinders can be hit and miss and the original AP type weep within weeks of fitting and usually fail within 12 months from my experiences.

Possibly a seal kit available

https://www.euspares.co.uk/parts/frenkit/7819781

From what I've found is people seem to believe it's the two small seals on the piston itself. Spending a few quid just to replace these two seals doesn't sound too bad to me

Does anyone have an original AP type master cylinder knocking about that they wouldn't mind stripping down and measuring the piston seal diameters and internal bore diameters?


---------
A part number I found that shows various BMW clutch master rebuild kits including the piston. * Not just a seal kit and are expensive.

Part number :- 21521158144
Merely placing this here for any future reference that may come in useful.. not ruling it out as a reliable possible option despite cost however.

Main focus of attention at the moment for me is just the rubber seals, this being the cheapest option.

[biffa75]

Original 75 clutch master cylinder stripped down.

Google search results of the part number. Very similar design piston, putting a little faith in the possibility that the pistons may be the same size etc.. afterall manufacturers of parts do sometimes use the same parts to save costs...just trying to locate the seals on their own to bring costs down.https://uploads.tapatalk-cdn.com/20221230/862614a2181e021ae21d2c5c10025147.jpghttps://uploads.tapatalk-cdn.com/20221230/d7cd2d1335c6d45cd105b40398424c56.jpg

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[biffa75]

A quick note *
Some of my replies within this thread are for me to refer to should I feel something may be of use or worthwhile etc.


Continued searching reveals that the grey seal as pictured is the cause of the fault.

Having spent a good number of hours searching online for any seal that looks even remotely similar has until this time has come to no avail.

I do have one or two spare old master cylinders and think I need to strip one down and see what's going on with my own eyes.

Has anyone else come across a seal similar to this grey seal?

Can't help but wonder if these seals are made from a material that is not brake fluid resilient like nitrile or something..

Is anyone aware of a general seal kit available? Like a hardware store sells large boxes of various size O rings for exame. This would at least allow to spend time test fitting different sizes and such..

Robhttps://uploads.tapatalk-cdn.com/20221231/02a908f728a36511dcd387aea65335c2.jpghttps://uploads.tapatalk-cdn.com/20221231/30c7e61dc4cec5be03d8395e531d490a.jpg

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[Ducati750cc]

Non of the ' seals ' in the master cylinder are ' o ' rings either of round section or square section, so finding any of the seals in a hardware mixed box will be impossible.


You would have to ensure that any you purchase other than in a kit are of exactly the same material compatible with brake fluid, exactly the same profile and dimensions and most important the exact shore hardness.


It would be a folly to change a single seal even if you could find one, they are all as old, all as worn as each other and removing and fitting the cylinder isn't the best task in the world.


The last one I changed was on my own Connie CDTI about a year or so ago, it had done 200,000 + miles.


I replaced it with a new original one, however the only one I could get was for a petrol ( different pipe ) no problem though, the pipe is held in the cylinder with a roll pin and when the cylinder is unbolted there is enough space to remove the roll pin and remove the pipe, having done this a few times over the years, there is non of the fun or for the extra time in routing a new pipe.


I fitted a full clutch kit several months previously, the old one was simply worn but the clutch action wasn't 100 %, hence the new slave.



I attached some pipe to the end of the clutch pipe and back flushed the pipework and the cylinder till clean whilst I was at it.


Removing the pipe from the new cylinder will lose brake fluid ( they are pre-filled ) but that's no problem, once the pipe and cylinder are fitted I simply fill and bleed from the slave cyl bleed nipple, when doing this I wedge the clutch pedal up to ensure that the piston is at its maximum rest position to ensure all air is expelled.


If it was me I would go with either a new cyl or a full kit sourced from a reputable company

[biffa75]

Thank you for your reply and advice is greatly appreciated ��

I understand your final comments of just replacing the whole unit however.... We have two 75 diesels of which, the tourer (my car) is actually now on its 3rd clutch master cylinder within 12 months of ownership or.. 10k miles. As my brother rightly pointed out, when we first got the car the one fitted (Luk branded) was leaking...

I'm getting absolutely fed up of spending £60+ on new master cylinders only for them to begin weeping within weeks of fitting them.

The tourer has had money, time and energy thrown at it by the bucket load.

Within the last twelve months of ownership/10k miles just in and around the clutch it's had:

Genuine BMW crank shaft oil seal
Clutch guide tube+ oil seal
Luk dmf
Luk pressure plate
Luk friction plate
Luk slave
Gearbox flush
Driveshaft oil seals
New AP master cylinder.

Within a couple of weeks of fitting the above we noticed the master cylinder was weeping... So kept topping it up every couple of weeks or so, got to the point where the internal seal was failing to even push enough fluid to the slave for it to be operated correctly

So... On with another new master again, AP... Which is now weeping again.

The wife's car has 150k miles on the clock on its original clutch and slave and master, the master was getting tired as the bite was near the carpet, a good second hand spare unit was fitted and hey.. nice light clutch and biting where it should, which has now failed (not actually too fussed about it failing in this instance as it was from a breaker as an emergency backup type option) both our cars are daily drivers.


Having a seal kit as an option to bring down the price by a fair amount is far more palatable than effectively the master cylinder becoming an annual service item.

It would seem somewhat silly to treat a clutch master cylinder as a serviceable item that is changed in its entirety when you change the oil and filters. It's just not reasonable.

It would seem the the Luk master cylinders arent any more reliable, nor are the tazu master cylinders from what I've read online.

If over 20 years ago the original ap master cylinders fitted when the cars were new lasted so long.. then why is it so difficult to replace it with the same brand component and finding such poor quality and them failing so rapidly. Surely it's just the best option to have the fault rectified with the originally designed and fitted part to regain that reliability the master cylinders once had all those years ago.

[biffa75]

another possibility...


https://www.rallydesign.co.uk/product_info.php?products_id=10438


Also

Tilton 74 series attachment for technical spechttps://uploads.tapatalk-cdn.com/20230103/b3c4923af9816b266298cf73c89a4748.jpg

[Ducati750cc]

another possibility...


https://www.rallydesign.co.uk/product_info.php?products_id=10438


Also

Tilton 74 series attachment for technical spechttps://uploads.tapatalk-cdn.com/20230103/b3c4923af9816b266298cf73c89a4748.jpg
It looks like they are both the same kit.


They look promising as long as the mounting holes line up, the bore, stroke, displacement and push-rod are the same, the mounting holes would have to line up exactly, though nothings impossible, there is no space to ' re-work ' any mounting holes.


One advantage with these kits is the ability to have a remote reservoir / filler in the engine bay, which could have been done from new and if I remember correctly someone on here has already done, something I think of occasionally myself.


However I'm very surprised at how many various new ones you've fitted in such a short time have failed, I could understand a bad batch of one brand, but not different brands !


As I've mentioned, I change them by disconnecting the pipe of the pre-filled unit and even though they are new I always flush / wash out the new master cylinder, in one instance with an original old stock item I found what looked like tiny glass spheres at the bottom of the reservoir, never seen before or since, which could, if not noticed wear both master and slave seals, possibly a one off ?


I took some photo's of them, if I can dig them out I'll post them, I never got to the bottom of where they came from though.

[biffa75]

Yes they appear to be the same kit but between the two I'd say the tilton might just have the edge.. simply because tilton supply lamborghini models so must be good for VAG to use them on such a brand.


I've measured the two mounting holes..
Original AP is 2cm's and this tilton 74 series is 3cm's however.. the mounting hole nearest the clutch pedal could have a metal bracket bolted in place using the original mounting location and the new tilton bolted to that using a nut and bolt arrangement.

I'm somewhat surprised at the failure rates myself, if I'm honest. The clutch isn't heavy by any means, doesn't slip and have no reason to doubt the rest of the hydraulic or clutch system. Having two diesel manuals I need a better solution than the current arrangement as two/three failures if you count the one the car came with inside twelve months, just on one car.. this becomes two cars with the wifes 75 that's an awful lot of money wasted on components you know are going to fail and quickly..

I've now got the removal and refitting of the master cylinder down to 40 minutes with basic tools. In fairness, I keep a spare used item in the boot with a small amount of brake fluid and basic tools to swap it over should it fail roadside.

Being able to use the original pipework and just tapping the split pin and roll pin out makes things quicker.
With this new possibility a braided line from Hel may have to be used similar to what some have done with the tazu units.

Having the remote reservoir up in the bulkhead next to the brake master as a possibility could be a good feature.

Glass spheres in the bottom? I wonder if someone may have put silica beads in the bottom to prevent moisture if you have split open one of those small packets of silica beads that come with trainers or shoes etc.. might be what it was?

Yes, if you can find those photos, would be worth a look, certainly strange.

[macafee2]

I wonder if this company can help in any way?
this is a page from their web site
https://www.sealsupply.eu/hydraulic-seals/rod-seals

There are other companies about. If they have to make the seal as a special order it will be expensive.

macafee2

[bl52krz]

Your paragraph about why are they not the same. Possible that a different compound is being used to make the seals? Not being so particular on the quality of the machining ofthe bore? It can not be any thing else. Can it? Should keep my mouth shut, but mine is still going after 20 years and 111,000 miles. But I do bleed it and also renew the fluid about every 4 years.

[biffa75]

thank you both for your replies,

macafee2 - i've actually contacted ap racing who used to own ap lockheed and they have given me the contact details of the company who bought ap so i will contact them about the issues with the master cylinder and see what they have to say. whether they actually look into the issue or not, but i will remain optimistic.

bl52krz - it could well be the seals inside the original unit that are at fault, possible substandard materials being used to make the seals, possibly a change in the way the seal works, possibly a material design change to the actual plastic body or simply tired tooling. as I say above in my reply to macafee2 - im going to contact the company manufacturing the units.

hopefully the attached PDF is viewable to anyone reading this. a quick thanks to any members who have also looked into this very issue over the years and have supplied much valued photos and information.

if you are unable to open the PDF attachment, members of this very forum in the past have noted that the original "grey" seal is of a rubber centre with the outer visible part with the ribs is more of a nylon harder plastic type material. which from what other members have said is this potentially expands under pressure to help form the seal between it and the bore.

quoting roverbarmy from 2017 Yes. After looking at pic 2, I managed to pull the end from the piston (as you showed in the picture) and the
grey, plastic seal (which also has a rubber section within it) just slides off. ( I had thought that the grey seal
was bonded ) I shall look at and measure the internal diameter of the seal and the internal diameter of the
narrower end of the cylinder to see if there are any standard seals available

further quoting roverbarmy I did notice that the grey, plastic seal seemed sticky in the cylinder, which could, combined with the blocking of
the end valve, give the occasional heavy pedal feel

also i'd like to quote marinabrian The main issue with the original AP master cylinder appears to be the blocking of the orifice in the piston which
is the makeup valve to return displaced fluid back to the reservoir, upon release of the pedal.


to quote frenchmike hum ! interesting .
for info,just measured on mine the external grey seal diameter =16.08mm
internal=6.00 mm

now i've been looking into things further found this photo on google https://i282.photobucket.com/albums/kk245/mattyprice4004/master3_zpsdf6c37a9.jpg~original

shortly after realising that it was posted by mat from DMGRS with the for sale post. I have messaged mat on the off chance he can remember what he used. I have found some very similar seals however i aren't sure what else mat may have modified for example the metal component on the end that wasn't there on the original AP units.

[Ducati750cc]

thank you both for your replies,

macafee2 - i've actually contacted ap racing who used to own ap lockheed and they have given me the contact details of the company who bought ap so i will contact them about the issues with the master cylinder and see what they have to say. whether they actually look into the issue or not, but i will remain optimistic.

bl52krz - it could well be the seals inside the original unit that are at fault, possible substandard materials being used to make the seals, possibly a change in the way the seal works, possibly a material design change to the actual plastic body or simply tired tooling. as I say above in my reply to macafee2 - im going to contact the company manufacturing the units.

hopefully the attached PDF is viewable to anyone reading this. a quick thanks to any members who have also looked into this very issue over the years and have supplied much valued photos and information.

if you are unable to open the PDF attachment, members of this very forum in the past have noted that the original "grey" seal is of a rubber centre with the outer visible part with the ribs is more of a nylon harder plastic type material. which from what other members have said is this potentially expands under pressure to help form the seal between it and the bore.

quoting roverbarmy from 2017

further quoting roverbarmy

also i'd like to quote marinabrian

to quote frenchmike

now i've been looking into things further found this photo on google https://i282.photobucket.com/albums/kk245/mattyprice4004/master3_zpsdf6c37a9.jpg~original

shortly after realising that it was posted by mat from DMGRS with the for sale post. I have messaged mat on the off chance he can remember what he used. I have found some very similar seals however i aren't sure what else mat may have modified for example the metal component on the end that wasn't there on the original AP units.


The grey plastic fitting at the end of the piston isn't a seal, it performs two functions, 1) it retains the valve and spring seen in one of the photo's in your earlier post and 2) acts as a guide to help to keep the piston assembly square in the bore, it doesn't perform any function in compressing the fluid, that's the job of the rubber seals, the one at the end of the piston in particular.


What exactly happens ?


Does the clutch action progressively fall off with no external leaks, or with external leaks ?

[Devilish]

when my clutch was replaced not too long ago I pondered on a genuine NOS master that are good quality and reliable, but did I did not fancy re-fitting the 20 year old plastic pipe onto a genuine master that is god knows how old. So I just went for a metal LR one with a copper pipe I bent into place. I pre filled the master and slave = no bleeding.