Leaking Slave Cylinder [Archive] - Corvette Forum : DigitalCorvettes.com Corvette Forums

: Leaking Slave Cylinder


Kubs
12-17-2007, 03:07 PM
My car (1990 Z51) seems to have a leaking slave cylinder. I looked at several part stores and they are all at $130.00 and upwards. Is there a rebuild kit that replaces the seals and o-rings etc. or anything inside that would make it leak?? If so, what is involved in replacing them?

Thanks

-=Jeff=-
12-17-2007, 07:29 PM
My car (1990 Z51) seems to have a leaking slave cylinder. I looked at several part stores and they are all at $130.00 and upwards. Is there a rebuild kit that replaces the seals and o-rings etc. or anything inside that would make it leak?? If so, what is involved in replacing them?

Thanks

There was a rebuild kit at one point, not sure if it is stil around or not.

As ofr a replacement, buy the 91-96 and the 91-96 line, the bleeder is in a better spot to get at on the 91-96. the down side is it is harder to bleed.

Kubs
12-17-2007, 08:02 PM
Why do I need the line too? What is different about it? How is it harder to bleed? (Sorry for all the questions)

-=Jeff=-
12-17-2007, 08:43 PM
Why do I need the line too? What is different about it? How is it harder to bleed? (Sorry for all the questions)

when you replace anything on the clutch you should replace all 3 piece actually., Mster Slave and Line.

Although your 90 line is rubber, newer is braided, I have alsobeen told the 90 style line will not work with the 91 slave

check out www.zfdoc.com

Also best way to bleed the clutch hydraulics is bottom up ( reverse bled) not gravity

olddog
12-17-2007, 08:51 PM
I seem to remember Bill telling me that he gets his slave cylinders elsewhere because most of the GM ones are now junk . . call him, he is a straight shooter.

I agree the later model slave/line makes things a lot easier.

Kubs
12-18-2007, 09:18 AM
Also best way to bleed the clutch hydraulics is bottom up ( reverse bled) not gravity

How do you do this? Sorry for all the questions I am new to a lot of the Corvette way of things. The last time I bled a clutch was the T-5 I put in my '76 Vega.

-=Jeff=-
12-18-2007, 09:40 AM
How do you do this? Sorry for all the questions I am new to a lot of the Corvette way of things. The last time I bled a clutch was the T-5 I put in my '76 Vega.

Taken from www.zfdoc.com:

Bleeding the Clutch Hydraulic System:
There are two versions ('89-'90, '91-'96) of clutch hydraulic Actuators (slave cylinder) for the C4 Corvette. The '89-'90 Clutch Hydraulic System actuator has the feed tube located at 12 o'clock and bleed tube at 10 o'clock. The '91 - '96 Clutch Hydraulic System Actuator has the feed tube located at 12 o'clock and bleed tube at 6 o'clock. This redesign makes the bleed fitting more accessible. Unfortunately, the bleeder horn repositioned to the 6 o'clock position complicates the bleed process due to the fact that air bubbles rise therefore rendering the reverse bleed method as being most effective approach to bleeding the system. Reverse bleeding is the process of forcing fluid into the system at the lowest point forcing the fluid back and upwards to the master cylinder fluid reservoir. This method will only be successful if no air is allowed to enter into the system during bleeding. WARNING: When pressure bleeding any hydraulic system it is necessary to provide the best seal possible around the bleeder fitting threads so as not to inadvertently draw in air as fluid is being pumped into the system. To achieve this affect, remove, clean and carefully apply 3 to 4 wraps of Teflon tape to the thread area only of the bleeder screw. Failure to follow this procedure will result in an improperly bled hydraulic system due to air ingestion during the bleeding process. NOTE: The best method that I have found so far in reverse bleeding these types of systems is to bleed the system until the fluid is clean and void of air bubbles, tighten bleeder screw, cycle the clutch pedal 50 times at varying rates and stroke depths, then perform one additional bleed before securing the tightening the bleeder screw to 18 Nm (13 lbs. ft.). Although bleeding can be done more simply by opening the Actuator bleeder and letting gravity draw fluid through the system, the following bleeding method will provide a more thorough evacuation of old fluid and particle accumulations.

'89-'90 Clutch Hydraulic System: The vehicle must be level front-to-back and left-to-right can be from level on up to 2 feet higher than the right side. The bleeding process is most effectively done by conventional method where one person actuates the clutch pedal while another opens and closes the bleeder after the pedal is depressed to the floor and before the pedal is let back up. After the bleeding process is complete, fill the reservoir to 1/16" below the "Low" mark so that when the "clean and dry" moisture barrier is re-inserted and lid screwed on, the fluid level remains between the LOW and HI mark. This set up method provides the best level of atmospheric pressure isolation with in the hydraulic system.

'91-'96 Clutch Hydraulic System: The vehicle must be in a level position both front-to-back and left-to-right when bleeding. The bleeding process is best done with a pressure bleeding system such as a "Phoenix Injector" or "Mighty-Vac". Bleeding of the system is best done by reverse flowing clean/new fluid, feeding the Actuator bleed horn located at the 6 o'clock position. Reverse pressure bleeding pushes the used fluid back upwards from the Actuator bleeder through the system on up to the reservoir. After the bleeding process is complete, fill the reservoir to 1/16" below the "Low" mark so that when the "clean and dry" moisture barrier is re-inserted and lid screwed on, the fluid level remains between the LOW and HI mark. This set up method provides the best atmospheric pressure isolation of the hydraulic system. WARNING: When pressure bleeding any hydraulic system it is necessary to provide the best seal possible around the bleeder fitting threads so as not to inadvertently draw in air as fluid is being pumped into the system. To achieve this affect, remove, clean and carefully apply 3 to 4 wraps of Teflon tape to the thread area only of the bleeder screw. Failure to follow this procedure will result in an improperly bled hydraulic system due to air ingestion during the bleeding process. NOTE: The best method that I have found so far in reverse bleeding these types of systems is to bleed the system until the fluid is clean and void of air bubbles, tighten bleeder screw, cycle the clutch pedal 50 times at varying rates and stroke depths, then perform one additional bleed before securing the tightening the bleeder screw to 18 Nm (13 lbs. ft.). Although bleeding can be done more simply by opening the Actuator bleeder and letting gravity draw fluid through the system, the following bleeding method will provide a more thorough evacuation of old fluid and particle accumulations.

olddog
12-18-2007, 09:43 AM
Just remember most of the GM slaves have degraded O rings - - try NAPA etc.

-=Jeff=-
12-18-2007, 09:46 AM
Just remember most of the GM slaves have degraded O rings - - try NAPA etc.


actually I believe all the DOM slaves are from the same MFG.

I had three, one each from, Carquest, Corvette America and GM. ALL had the backwards seal, but this was just over 18month ago.. might be fixed now

olddog
12-18-2007, 09:59 AM
Jeff,

Interesting - - if anyone knows it would be Bill Boudreau.

Kubs
12-18-2007, 10:01 AM
Well I made a couple calls and it seems the better way would be to go with the new one. Thanks for all your help and info. One more question, the only place I could find the braided hose was from a dealer for $140!! Is there a cheaper place to get that hose from?

Kubs
12-18-2007, 10:27 AM
Better yet does anyone know what size fittings go on the master ans slave cylinder? I might make my own stainless line.

-=Jeff=-
12-18-2007, 10:35 AM
Jeff,

Interesting - - if anyone knows it would be Bill Boudreau.

Yeah I helped Bill with the slave issue by taking the 3 I had apart

Kubs
12-19-2007, 09:38 PM
What is different about the two lines that would make the one I have not work with the newer model?

96CERon
01-01-2008, 01:18 AM
My slave cylinder failed and I could not find one right away nor could I find a lip seal. So down the oring house I went and found an oring (nitrile) that fit reasonably well. It was a little harder to assemble and a little harder to bleed. It has been working for 18 months in daily driving.

-=Jeff=-
01-01-2008, 07:16 AM
What is different about the two lines that would make the one I have not work with the newer model?

well I have heard that is should, but I have also heard that guy have had issues.

it is best to swap the line anyway.. just read the info on Bill's website www.zfdoc.com

pacat
04-06-2008, 07:13 PM
My slave cylinder failed and I could not find one right away nor could I find a lip seal. So down the oring house I went and found an oring (nitrile) that fit reasonably well. It was a little harder to assemble and a little harder to bleed. It has been working for 18 months in daily driving.

Do you still have the part numbers and brand name of the o-rings you purchase for your slave cylinder? Also the store/company you purchase them from? I need to rebuild or buy a new slave. I haven't been able to find any rebuild kits for the slave or master cylinder. thanks

96CERon
04-07-2008, 11:29 AM
I went to a place here in Phoneix called Martin Fluid Power and got my oring there. I will check when I go home tonight to see if I still have the number. It was a Buna N or Nitrile which everyone says is not compatible. I have had this oring running for more than a year and I put one in a jar of brake fluid--it still has not changed size or degraded.

pacat
04-07-2008, 07:24 PM
Here is a letter I wrote to ZFDOC asking for info on rebuild kits (o-rings) for the ZF clutch system. Looks like no rebuild kits.


I have a 1993 Corvette with the ZF 6 speed. I need to rebuild or replace the clutch master cylinder and also the slave cylinder. I can not seem to find a rebuild kit for ether part.

Do you know of any rebuild kits available or do you know of aftermarket o-rings that can be used? Thanks any help would be appreciated.


Reply:
There are basically only two manufacturers of the C4 6-speed Clutch Hydraulic System (CHS) and they are TRW and Wagner.

The TRW design is the OEM source and is of a Drawn Over Mandrel (DOM) steel design.

The Wagner aftermarket source (1/2 the price) is constructed from cast iron.

With the exception of the GM (TRW) CHS cylinders having a more advanced design Actuator cylinder seal, all of the seals, between the two manufacturers, are the same.

With the exception of NAPA selling rebuild kits up until about three years ago, over the last four years, we have not been able to find a single source for these seals.



Regards,

Bill Boudreau

96CERon
04-08-2008, 11:39 AM
I spent a day talking with all manufactueres of seals to find a lip seal to replace the one in the slave cylinder with no luck and therfore went to the the oring. It is a tight fit and stiff at first and hard to bleed but it is working well. I did make sure I can get a good volume in the reservoir bymaking sure that the filler seal under the lid is folded back and up in the lid--like a normal master cylinder unit. Hiope that makes sense.