Lifespan of a clutch master cylinder

JKIDD

True Classic
Yesterday I felt a drip on my left foot. Yup, the clutch master seems to be weeping out the end. We all know what a fun job this is & this will be my 3rd time in our relationship I've replaced it. I have done it in & out of the car. I did both the clutch & brake by removing the pedal box 5 years ago. I purchased them from Rock Auto. I should have know this may happen as the brake master was defective out of the box, so yes I had the pedal box out twice on this job. No matter what I did, it would not bleed. The warranty replacement had no issues. This time I ordered the MWB unit.
My question is, how long do these typically last? It was maybe 1000 miles ago.
 

kmead

Glutton for punishment
Yesterday I felt a drip on my left foot. Yup, the clutch master seems to be weeping out the end. We all know what a fun job this is & this will be my 3rd time in our relationship I've replaced it. I have done it in & out of the car. I did both the clutch & brake by removing the pedal box 5 years ago. I purchased them from Rock Auto. I should have know this may happen as the brake master was defective out of the box, so yes I had the pedal box out twice on this job. No matter what I did, it would not bleed. The warranty replacement had no issues. This time I ordered the MWB unit.
My question is, how long do these typically last? It was maybe 1000 miles ago.

I replaced mine on my 1985 in 1993 at @46k miles with a replacement from Art Bayless (I had replaced the seals on the slave a couple of months before). So far so good, it worked last week when I took it out of storage for a brief drive and again yesterday so hopefully I get another season out of it.

So on my car the OE one lasted 8 years, the replacement has lasted 29 and the car is around 65k I think but it might be less.

Modern ones are to a different design (or so it is said) and may not last as long.
 

Vagone

Daily Driver
Yesterday I felt a drip on my left foot. Yup, the clutch master seems to be weeping out the end. We all know what a fun job this is & this will be my 3rd time in our relationship I've replaced it. I have done it in & out of the car. I did both the clutch & brake by removing the pedal box 5 years ago. I purchased them from Rock Auto. I should have know this may happen as the brake master was defective out of the box, so yes I had the pedal box out twice on this job. No matter what I did, it would not bleed. The warranty replacement had no issues. This time I ordered the MWB unit.
My question is, how long do these typically last? It was maybe 1000 miles ago.
My experience with the same master in my Scorpion is.... not very long. Even buying them from our Fiat parts suppliers I have had the same issue. Granted it sits for long periods of time, but my lastest is only a few years old and it is dripping again when I depress it. This is the 3rd one in 12 years. I should just take it to a machine shop and have it sleeved with aluminum. It seems the cast iron housing corrodes internally quite quickly. I have cars with aluminum clutch and brake masters thet are 25 years + and they have never leaked. Considing the location in the X and Scorpion / Monte Carlo, it should be very reliable.
 

JKIDD

True Classic
I replaced mine on my 1985 in 1993 at @46k miles with a replacement from Art Bayless (I had replaced the seals on the slave a couple of months before). So far so good, it worked last week when I took it out of storage for a brief drive and again yesterday so hopefully I get another season out of it.

So on my car the OE one lasted 8 years, the replacement has lasted 29 and the car is around 65k I think but it might be less.

Modern ones are to a different design (or so it is said) and may not last as long.
I've had a similar experience. Replaced the OEM from my 86 around 1994 & in the 50k mile range. Used the MWB unit then & it made it to 2017, around 15k miles with a lengthy storage. Hopefully the new MWB unit will yield similar results.
 

JKIDD

True Classic
My experience with the same master in my Scorpion is.... not very long. Even buying them from our Fiat parts suppliers I have had the same issue. Granted it sits for long periods of time, but my lastest is only a few years old and it is dripping again when I depress it. This is the 3rd one in 12 years. I should just take it to a machine shop and have it sleeved with aluminum. It seems the cast iron housing corrodes internally quite quickly. I have cars with aluminum clutch and brake masters thet are 25 years + and they have never leaked. Considing the location in the X and Scorpion / Monte Carlo, it should be very reliable.
How long will it just occasionally drip? Any danger of it blowing out?
 

kmead

Glutton for punishment
Bernice has strongly suggested getting an OE one sleeved and using the OE internals. She has covered this along with the supplier she uses in her threads around making a reliable pedal box assembly.
 

Dr.Jeff

True Classic
It's not only miles of use, but just time. Especially sitting without being exercised the seal goes bad and leaks. What will happen if you ignore it? Your clutch will rapidly quit working and your shoes will get ruined. I'm with the others, it seems the current offerings of replacement cylinders (globally) is not very good and don't last long. It is costly to have a new one resleeved as suggested but that might help. I also wonder how much of the problem is the quality of the seal itself? You can buy rebuild kits (with the seal) from aftermarket makers that might be higher quality than the ones that come in the new cylinders. I wonder if it would help to install a better seal into a new cylinder initially?
 

carl

True Classic
If the MC was easily accessible, like the one in my Miata then this would be a mere annoyance but swap out done in an hour, including bleeding. Having to do this on an X puts most of us into episodes of depression. Maybe it's time to come up with a cable conversion...like for a 128.

I agree, non-use is probably the main culprit.
 

Ics19

belle macchine!
It seems the cast iron housing corrodes internally quite quickly.
I wonder how much the age of the fluid contributes to failures, given that it's hydroscopic - even the newest FIAT service book says "Replace brake fluid every 2 years regardless of the distance travelled." - probably more of an easy earner for the service shop than strictly necessary, and likely playing on the wise side for brakes from a safety critical point of view 😬
 

TonyK

True Classic
Contaminated fluid is the reason for the internal corrosion of the cylinder.
Right on. And what caused the contamination...moisture. Humid air that contaminates the fluid because Dot 3 and 4 will adsorb moisture. What I do is use silicone Dot 5 brake fluid. It does not absorb moisture and I have had brake and clutch masters and slaves last 25 years. You could bleed out the fluid every year which could prevent this, but I would rather use Dot 5 Silicone fluid and not bother bleeding every years.

TonyK at Bob Martins in Radcliff Kentucky.
 

Cratecruncher

True Classic
I still give myself a kick in the backside every time this topic comes up. I had the entire brake and clutch system apart for a rebuild a few years ago and didn't convert to DOT 5. Doh!
 

Bjorn Nilson

True Classic
I still give myself a kick in the backside every time this topic comes up. I had the entire brake and clutch system apart for a rebuild a few years ago and didn't convert to DOT 5. Doh!
I am going to bleed my brakes and clutch as I probably cooked the break fluid last time at the track. Is DOT 5 better than DOT 3 or 4? What kind of conversion is needed to run DOT 5 and is it worth the effort?
 

ng_randolph

Bjorn H
It is a bit like asking what motor oil to use; lots of strong opinions. Some people swear by DOT 5 (silicone based), which is not compatible with other types. I would look at DOT 5.1 instead. This is conventional glycol-ether based brake fluid just like DOT 3 and DOT 4, but with a higher temperature rating. DOT 5.1 is compatible with DOT 4 and DOT 3, so no elaborate change-over procedure needed.
 

Cratecruncher

True Classic
Bjorn, my understanding is that DOT 5 has a lower boiling point than DOT 3 so if you aggressively track the car you'd probably be better off staying with what you currently have and focus on better heat rejection, The advantage of DOT 5 is it's silicone and will not absorb moisture over time making it ideal for lightly used cars that sit up for extended periods. Since the two are so different cross contamination is also an issue to be avoided when converting. Ideally you would switch after a full rebuild but a thorough flush might be sufficient.
 

Dr.Jeff

True Classic
I agree with the points made; each has it advantages and disadvantages (as has been noted). So like they said, it likely comes down to your intended use of the car. Track use may benefit from the higher boiling point of DOT 5. Extended storage intervals may also benefit from DOT 5 (*see note below). However DOT 3/4 is easier to live with, mostly due to its general compatibility. And it is much less expensive if you go through a lot of fluid (frequent bleeding and/or flushing). Plus it works fine for normal road use.

Traditionally I've used DOT 4 in my vehicles. But they are not track cars and they get serviced (kind of) regularly. However given the Fiat's propensity for hydraulic issues, for me the decision may come down to which fluid might help prevent failures. Has anyone found any distinct advantage or disadvantage for DOT 5 vs DOT 3/4 with the Fiat seals? I'm not referring to cylinder corrosion from moisture contamination, but actual rubber seal life. Is there any difference? I've read that some vehicles come with seals specifically made for use with DOT 5 and using DOT 3/4 will cause problems with those seals. I've also read that DOT 5 actually has less lubrication property than DOT 3/4, which might cause accelerated seal wear. Furthermore I'm told one maker of hydraulic seals will not honor the warranty if DOT 5 has been used. So could the Fiat's seals (made for DOT 3) have issues with DOT 5? Not sure.

Another consideration for DOT 5 in a Fiat is it's tendency to trap air within it (more so than DOT 3/4). This can make bleeding the system more difficult with DOT 5. And given the X can already be difficult to bleed this might make things worse.

* Regarding DOT 5 and water absorption. I've heard arguments saying the lack of moisture absorption (i.e. DOT 5) could be a bad thing. For the typical vehicle that gets very little moisture into the hydraulic system, having a fluid that absorbs it (i.e. DOT 3/4) will keep the water from damaging metal parts....provided the fluid isn't left in there forever. While DOT 5 will allow that water to pool in places and cause more damage. Honestly I'm not certain which is better.
 

Cratecruncher

True Classic
My understanding is that DOT 5 silicone has a slightly LOWER boiling point than DOT 3/4 so racers tend to avoid it. Some manufacturers say not to use DOT 5 in ABS equipped cars, which basically means everything built after 1995! My personal experience is that I have to flush black goo out of my C5 (with ABS) every 3 to 5 years but have let cars and bikes sit up in long term storage with DOT 5 for twenty years and the brake and clutch works perfect and the fluid looks brand new.
 

myronx19

True Classic
bah - this is frustrating. I put in a new set about 25 years ago (from Art Bayless) - and it leaked the very next year. Now, I've been too lazy to change it so it's still been working (and leaking!) for 25 years! Finally my slave has started to leak, and that's because I haven't changed the fluid - probably in 25 years. :(

Has anyone tried the LPR brand brake and clutch master/slave? They are made in Italy. Any issues? No stock for the brake master - that's the only issue :(

I have a set of Brake master and Clutch master/slave from MWB that I bought a few years back - either I use those, or spend a LOT more and get a spare set of Fiat OE parts sleeved in stainless and hope it never leaks again. Sleeving is not cheap! But I don't want this to leak again.

Hopefully I remember to change the brake fluid every few years after I change these!
 

Dr.Jeff

True Classic
bah - this is frustrating. I put in a new set about 25 years ago (from Art Bayless) - and it leaked the very next year. Now, I've been too lazy to change it so it's still been working (and leaking!) for 25 years! Finally my slave has started to leak, and that's because I haven't changed the fluid - probably in 25 years. :(

Has anyone tried the LPR brand brake and clutch master/slave? They are made in Italy. Any issues? No stock for the brake master - that's the only issue :(

I have a set of Brake master and Clutch master/slave from MWB that I bought a few years back - either I use those, or spend a LOT more and get a spare set of Fiat OE parts sleeved in stainless and hope it never leaks again. Sleeving is not cheap! But I don't want this to leak again.

Hopefully I remember to change the brake fluid every few years after I change these!
I hate to say it but those new cylinders from MWB a few years back are likely no good now. The seals tend to go bad even when sitting unused.

And that is one reason I'd be reluctant to spend the money on resleeving. That still won't cure any seal issues.
 
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