I had a problem with the slave pulling in air. The fluid level was rising in the master. It got to the point where it was drawing air as fast as I could bleed it. So I pulled it all apart and took some pics and found a very cheap way to fix it.

Here are all the parts inside


With seal in place


Since the seal didn't seam to be working well or at all. But it wasn't realy leaking fluid out the slave. I got an O-Ring to fit on the front part of the old seal.


With the O-Ring in place


Alignment of parts


Where I put the O-Ring


After 150 mile test today it still works GREAT,.... so far
I gravity bleed the line then with the resivor cap off and the slave full of fluid I quickly hooked up the line.
And it cost me nothing$$ since I had some O-Rings around, sry I don't know what size I used either just what fit.

Well I hope this helps (and works for a long period) It seem like it will.


------------------
"DRIVE IT LIKE A FIERO"
'84 Fiero, engine to be determined
'87Blue GT 3.4L Swap Completed!!!!!!!!
http://www.lasvegasfieroclub.com/

[This message has been edited by sardonyx247 (edited 08-16-2006).]

Super wicked man - that's an excellent fix, assuming it holds together I might have to do that as soon as mine acts up again, which it will. grr.

As I posted in another thread, the reason that the slave seal gets destroyed is because of heat. Although it isn't pretty, I wrap mine in 3 layers of HD aluminum foil, shiny side out, to act as a heat shield. I have never had a problem with a slave that was in foil. I have had a slave die 3 times when it was unprotected.

Nice fix btw.

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More info at: https://www.fiero.nl/forum/Forum1/HTML/043357.html

Still holding strong, I wish I did this before. Such an easy fix for such a long PITA problem. Someone once said "If there was a second seal it wouldn't leak in air" So I decided to find a way to add the second seal. Sure enough I found one and sure enough it works.

------------------
"DRIVE IT LIKE A FIERO"
'84 Fiero, engine to be determined
'87Blue GT 3.4L Swap Completed!!!!!!!!
http://www.lasvegasfieroclub.com/

Thats odd that yours didnt have an o-ring to begin with. That looks like a stock Isuzu/Muncie type slave. I had the OEM one on my car and took it apart to find the umbrella seal AND an o-ring installed in a second groove on the piston. The aftermarket pistons always leave out the o-ring.. arg.

quote Originally posted by Steven Snyder: Thats odd that yours didnt have an o-ring to begin with. That looks like a stock Isuzu/Muncie type slave. I had the OEM one on my car and took it apart to find the umbrella seal AND an o-ring installed in a second groove on the piston. The aftermarket pistons always leave out the o-ring.. arg.

It is an Isuzu slave see https://www.fiero.nl/forum/Archives/Archive-000001/HTML/20060811-2-069597.html

What they are supposed to come with one.?.?.?.? I pulled apart two slaves and neither one had an O-Ring.

quote Originally posted by Bigfieroman: As I posted in another thread, the reason that the slave seal gets destroyed is because of heat. Although it isn't pretty, I wrap mine in 3 layers of HD aluminum foil, shiny side out, to act as a heat shield. I have never had a problem with a slave that was in foil. I have had a slave die 3 times when it was unprotected. Nice fix btw.

Or it could be you are just keeping the alien transmissions out of the slave :P
Do you have the heat sheild for the slave to start?

Figured I'd bump this as there are always slave problems

quote Originally posted by sardonyx247: Figured I'd bump this as there are always slave problems

I'm glad you did. I have the same issue due to a warped clutch... This fix may save me having to replace the slave when I replace the clutch. { : ]

Red 5spd Formula (foot massager)
Trot, the gray, fox...

Awesome!

I'm going to try this, soon...

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Patrick W. Heinske -- LZeitgeist@aol.com
1988 Red Fiero Formula Convertible
*Desktop Photo Here* (click either link for pics)

Does it matter what material the "O" ring is made of? I'm not knowledgeable on the subject, just asking if certain rubber, neoprene materials may be subject to deteriorating when exposed to brake fluid?

Wow, timing could not have been better.

I keep getting air in my clutch line, but I am not losing fluid. I have replaced the clutch master cylinder . No change. Now I have been reading about the slave cylinder sucking in air. I still can't figure how air can get in, but the fluid can not get out, but hey, I will try anything at this point.

I was trying to change out the slave cylinder with an aftermarket one when I ran up on this. I know what everyone has posted about aftermarket slaves, but that's all I could find locally. This fix may allow me to keep the stock slave cylinder.

When choosing a O-ring are we using it to as another seal between the piston and the cylinder wall or as a spacer of some sort?

haven't taken my 88 getrag slave apart yet. Can I add or replace an o-ring?

quote Originally posted by dratts: haven't taken my 88 getrag slave apart yet. Can I add or replace an o-ring?

Same here. I can't break my hydraulic line free from the slave cylinder. I will try to rebuild while on the vehicle rather than trashing the hydraulic line. Does anyone know where you can buy the rebuild kit for the factory slave cylinders?

[This message has been edited by sjmaye (edited 03-04-2007).]

Just a note, the rebuild kit does not have an o-ring and for the Getrag slaves cannot even support an o-ring because the piston on fluid-side of the umbrella seal has no lip to secure it. I'm working on putting together a seal and piston kit that actually works (i.e. has a decent seal and o-ring).. but it'll be another month or so until I get some made.

This is what the aftermarket pistons (which are the same as what is in the rebuild kits as far as I know) look like:

Obviously you can't put an o-ring behind the seal there and expect it to stay..

I am still perplexed on how the air is getting by the umbrella seal. The only solution I can guess at is second umbrellla seal pointing in the other direction.

Here is my reasoning. The rubber boot around the slave cylinder body and the shaft coming out creates an almost perfect seal. You can feel the compression of the air in the boot when you manually push the shaft back in the cylinder body. When the clutch is depressed the hydraulic fluid in the line and slave cylinder body is compressed and forced against the umbrella seal. The pressure in this direction causes the seal to flare out and further enhance sealing.

When the clutch pedal is released the hydraulic force is gone, hence the push against the umbrella seal is gone. The pressure plate pushes the extended shaft back in to the slave cylinder body. This creates air pressure in the rubber boot sealing the shaft and the body. The pressure must escape so it follows the path of least resistance which is right by the umbrella seal in to the slave cylinder body,

I know. That is far fetched, but I am at a loss to find another reason.

Just my $0.02.


PS- The price of the rebuild kits seems sort of high. Why do they include the spring and piston when all you seem to need is the seal? If only we could find just the seals.

quote Originally posted by sjmaye: PS- The price of the rebuild kits seems sort of high. Why do they include the spring and piston when all you seem to need is the seal? If only we could find just the seals.

In my master cylinder, I found the spring in four pieces, so they sometimes can break. I must not be the only one, and that's probably why they include the spring in the kit.

Edit to add that I too filled the boot with grease and have had good success thus far. I also put a heat shield on the slave.

[This message has been edited by TG oreiF 8891 (edited 03-05-2007).]

i agree with your asumption sjmaye.i had the same problem and idea that the boot was pushing air past the seal.i just filled the boot with high temp grease and have had 10,000 trouble free miles so far.

quote Originally posted by brokeagain: i agree with your asumption sjmaye.i had the same problem and idea that the boot was pushing air past the seal.i just filled the boot with high temp grease and have had 10,000 trouble free miles so far.

Thanks Brokeagain.

I thought I was going crazy, but now at least there are two of us.

One question- If you fill the boot completely with grease, where does the grease go when the shaft/boot are compressed by the pressure plate?

Is it air getting into the system or is it the water that the old brake fluid has absorbed hitting it's boiling point and turning into steam thus creating a compressible gas from what used to be a noncompressible liquid? As far as the grease is concerned, I'd be wary of petroleum based grease as it may cause issues with the rubber seals. On the other hand, it's the clutch that'll go out and not your brakes, so I guess that's the worst that can happen.

by boot is good and tight, i also filled it with grease while it was compressed.

How are you getting the grease into the boot? I picked up a tub of grease and fought like mad to get the rubber boot backed off and now am wondering how to get the grease in there without making a huge mess... then the really hard part will be getting the boot back on..

quote Originally posted by brokeagain: i agree with your asumption sjmaye.i had the same problem and idea that the boot was pushing air past the seal.i just filled the boot with high temp grease and have had 10,000 trouble free miles so far.

I rebuilt the slave cylinder with parts from the Fiero Store and created tiny vent pin holes in the boot. The thing works like a champ. The best clutch pedal I ever had.

I guess I should have remembered the KISS principle. Considering my car has 120,000 miles on it and is 20 years old. Maybe it just worn out?

[This message has been edited by sjmaye (edited 03-20-2007).]

Cool I need to do this fix, my clutch is real weak

I just did this... I hope the o-ring wont disintegrate with the dot 3 fluid..

Greasing the slave cylinder bore is a good idea. There's a wide range of temperature experienced by the slave cylinder; as it heats and cools air is drawn in and expelled from the boot. The moisture in the air gradually corrodes the bore, leading to a pitted surface.

This is all happening on the "dry" side of the slave piston and doesn't cause any trouble at all - until clutch wear causes the piston to move out onto the pitted bore surface. Then it can't seal and you get leakage.

You don't need to fill the bore with grease - just give the walls a good coat so that they're protected from rusting. This'll make your slave last a long, long time.

quote Originally posted by Matthew_Fiero: Still holding up for you sardonyx247?

Yeah it is still holding up great, I don't even think I have bleed my system since this I did this.
(Thinking hard) no, I have not had to bleed it once.
I have noticed this does not work for all slaves, on some the o-ring just won't fit, I forget what year and model does not work.

------------------
"DRIVE IT LIKE A FIERO"
'84 Fiero, engine to be determined
'87Blue GT 3.4L Swap Completed!!!!!!!! Boosted!!!!!!!
Las Vegas Fiero Club
Fiero Road Club Of Northern Nevada