924Board.org

[positivesale]

What is it with these slave cylinders and masters blowing out prematurely on the 931? I hear 944 owners with the same problems. Same exact parts on the 944s - lots of people replace these things yearly. They SHOULD last longer..

They keep failing on my car. Drive the car for one year, rarely...not doing very big miles here. Just like 2000-5000 miles max a year. And it fails. OVER AND over and over again. Either the master, and/or the slave, both at the same tiem or near the same time. They fail, the brake fluid goes black...even after replacing parts in and out. The fluid is new, and changed so frequently I have brake fluid bottles everywhere in the garage. (No, it's not old fluid I'm using..I'm using new sealed container fluid).

I put in a NEW slave and it failed a few hundred miles down the road. Maybe a few thousand miles if lucky. It's not a rebuild but a new part. So I'm now at the stage of thinking the rebuilding is the better way to go along with some other solution like lining the bore? I use good brake fluid and replace often yet it still turns black and the slaves and masters keep draining my wallet. Is it the temperature under the hood or the hot turbo engine compartment that's helping these things fail, or what? I barely drive the car and they fail so often and I live in a cold climate, so it can't be the engine heat as the main cause.

What I noticed when I pulled my slave out .. is that the metal inside the bore has different colors on it. Like different minerals or whatever it is. So I rub it gently and try to smoothen it out. Works somewhat, but I'm SURE that this will just keep failing if I put a new seal in. Buy a new slave cylinder and the same problem. It fails early. Is FAG in this game to make money or what? I shouldn't' have to replace slave cylinders every year with driving the car rarely.
Anyway some the metal in the bore is black and rougher feeling if I run my nail on it. It's not rough rough, but I can feel a difference in texture compared to other parts of the bore. IS this crappy steel? I'm sure that this un-smooth deposit like stuff in there is causing the seal to fail..as a seal should be running up against even smooth metal, not metal with black un-smooth deposits embedded into it! So honing would help, you would think. But no, this stuff GROWS back. It's black and embedded into the metal..Crappy steel?
It's as if the metal in these cylinders by FAG are DESIGNED to go bad. I rub down the surface a bit.. till it's smooth. Then leave it overnight and it's rough again. They rust very easily, so any bit of water in the brake fluid must attack them too. But what I don't like is the fact that they are rough on certain parts. Even if you hone the metal down, after a few days the minerals or whatever it is in the metal just roughens up on certain spots. Then the seal blows because it's getting eaten away. What I've found, is that the brake fluid goes black. I thought it was the rubber that made the brake fluid black. It seems it's the cylinder wall of the slave and master..because when I rub the cylinder wall gently with my finger and a bit of baking soda it goes black. Is this crappy stainless steel? It's not very smooth metal..it's smooth for a few seconds but then after a few days or months the seal blows because the surfaced roughened up.

I purchased a new slave cylinder instead of rebuilding it...and it just blew a few months later. IT seems all these FAG or ATE slave cylinders are junk. What I don't understand is why other german cars with the same FAG part have less problems. Unless they have the same problems. I know mazda miatas have problems with salves. I don't know what the solution is, possibly to chrome or dip the cylinder some how and line it? I just can't stand having my slave cylinder leak or blow a seal after only a few thousand miles of driving. That and seeing the brake fluid go black with almost all new hydraulic parts. What next, my brakes fail on the highway? Why is it that these silly clutch cylinders blow out but not the brakes?

I guess what I need then is for someone to tell me if bores can be dipped, lined, or if there is some solution to this problem of the surface roughening up with deposits. Is there some additive that I can put in my brake fluid to make things wear slower? I've bought several new cylinders and replaced them, because I figured if the metal is bad I'll hit it with luck and get a good one. But they all fail on me..so I want to solve my problem with the spare cylinders I have lying around..which leads me to the question?? can I dip these things, get them bored and dip, get them lined, is this possible>? I'm sick of buying new slave cylinders only to find that they fail a few hundred miles down the road.

Imagine having to replace your engine every 1000 miles down the road because the bores kept getting rusty while you were parked. That's the way I feel with this slave cylinder.. it just keeps failing..it's either cheap seals they use, poor design, cheap crappy steel with mineral deposits embedded in it, or badly mixed steel possibly. This metal in these cylinders seems far to sensitive, and hence causes the seal to leak and fail prematurely. And rebuilds don't last because the surface seems to roughen up or the seal gets eaten by something else (my theory is surface roughening since every slave I pull out is rough, but was smooth when put in).
It cant' be water in my brake fluid, considering the amount of money I've wasted changing my brake fluid so often to try and lessen the problem!

PS: I'm not making crap shots at the slave cylinder by calling it a FAG. Yes, it's actually designed by a company called FAG. Where'd they come up with that one? I'm beginning to think the company name they chose has something to do with their quality of steel they use. No insult intended to fags.

I used to get slave cylinders for $50 locally and now price has gone up to $180 . So I figure a rebuild kit, and a bore lining or some other fancy shitwork is needed. Someone help me with this neverending battle with the slave and master.
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82 931

[wdb]

I'm not an expert, but I think whatever it is thats building up on your slave, has probably completely covered the inside of your brake lines . and the lines might be the problem or the source of the contamination .ya never know what the previous owners did to your car .may be time for new lines ,and clean out the wheel cylinders . couldnt hurt .

as for the slave and other parts, any metal part can be crome plated , you wouldnt have to bore it out the plating is microns thick .and a small part like that shouldnt cost much . and you should buy a set of brake hones , using a drill to polish the bores of the slave and wheel cylinders to remove any imperfections . here's a link to some

http://www.autotoolexpress.com/braketools1.html

[924RACR]

That's really not right. I just replaced mine in my 81 931, new FAG master and slave (ooh, that sounds kinky! ) from Paragon. I think the slave was like $40. However, that sounds really odd. I'd have to agree, maybe you're getting contamination. Maybe the hose from the master to the slave? How abou the hose from the reservoir to the master? Have you replaced that? It could be letting the water in. Or you could be getting water from the reservoir itself, if it's not sealed well.

The metal coloration you refer to indicates wear through the bore - not right. Is your clutch perhaps sticking, problem with the release tube or throwout bearing? However, with all the discoloration and rusting you are referencing, I'd fix that problem first, including a flush of the entire brake system.

My 82 931, I have had for 2 years, clutch hydraulics were fine when I got it, no problems yet. (knock on wood)

Tell us more about your brake fluid? What kind/type?
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Roger]

You might want to go to http://forums.pelicanparts.com/forumdisplay.php?s=&forumid=10 and ask some people there. I have read post about the master and slave cylinders failing but yours is extreme.

What type of fluid is used in the clutch? I think the previous post are correct. You probably have some contamination in the system. Have you noticed any rust?
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1981 924 NA

Some people are like Slinkies. Not really good for anything, but you
still can't help but smile when you see one tumble down the stairs.

[Smoothie]

The hydraulic clutches on these cars probably fare better when they're used regularly. It popped to mind recently while working with the slave cyl that the normal resting (pedal up, not being used) position of the plunger inside the slave, is fully recessed. This leaves the inside walls of the slave not covered by fluid or protected behind the seal. There is that rubber bellows-type seal that's intended to protect from the outside elements, but they seem to fail easily. Every time I've removed the slave, that bellows seal has been split somewhere. It's entirely plausible that with the low down position of the slave combined with the common absence of the clutch inspection port cover, that the slaves are left open to corrosion damage.
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[wdb]

smoothie I think right .hmm . I was thinking maybe a gob of bearing greese would prevent the rusting , but the thin film of brake fluid would break down the greese over time , might extend the the time between rebuilds though .

[Ordrune]

The clue here is the colour of the metal in the cylinder bore......

blue/black/purple indicates annealed metal or hardened metal. In order to harden metal it has to be hot and then suddenly cooled. for this to happen I'd be willing to bet that snow or water has hit the slave cylinder after the engine had warmed it up (5 mins on a turbo) and gave the cylinder a nasty case of thermal-shock. As you said the multicoloured metal is rough and this will chew cylinder seals in no time. This also puts little black bits of rubber through the fluid turning it black much the same way sulpher turns diesel oil black. We had a similar problem on a transit van we used to take to the snow every year which we fixed by making a guard for the slave cylinder with enough room around it to let the air flow and keep it as cool as possible.

I usually change brake fluid every two years without problems(Ive seen cars go 20 years on the original fluid) so as you have stated the fluid is clean. The metal lines cost next to nothing, just measure how long you need them and cut one end of the metal line to get the thread, pipe & flare size. Take it down to any brake specialist and they will have a new one made in about five minutes for under $50.

Good luck
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'79 924 supercharged,intercooled

[Lizard]

try flushing the brake system and replace hose between the master and brake resevior, then warp the master slave, and brake line between the 2 in a protective waterproof material (Dynomat?) a couple of layers, that will prevent cold shock and help to hold the tempature steady
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3 928s,

[Paul]

My 80 931 has the original slave and master cylinders, had to replace both hoses a few years ago.

[numbbers]

My '80 has the originals also. The only problem I know of with the clutch on the 931 is that they are a bear to bleed.
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1980 924 Turbo