Clutch Questions
Thread Starter
Pro
Joined: Feb 2003
Posts: 715
Likes: 21
From: Ontario California
Clutch Questions
I have a few questions concerning the hydraulic clutch system on the C4's. I have a 94 coupe, with about 110,000 miles on it, and was wondering what is the average life of the master and slave cylinders, when can you expect some problems? Just wondered if it is wearing out, or slowly losing fluid, if it will show up in shifting problems.? 
Also..what's the deal on using hydraulic fluid? I have heard that once you open a bottle of hydraulic fluid, you should use it all, or throw it away, because if you keep it a long time, even though it is sealed, it will tend to get moisture in the fluid. Since this stuff for the clutch isn't cheap....at least not the GM stuff from the dealer, I would hate to throw it out, if its still good. Comments? suggestions? thanks
Also..what's the deal on using hydraulic fluid? I have heard that once you open a bottle of hydraulic fluid, you should use it all, or throw it away, because if you keep it a long time, even though it is sealed, it will tend to get moisture in the fluid. Since this stuff for the clutch isn't cheap....at least not the GM stuff from the dealer, I would hate to throw it out, if its still good. Comments? suggestions? thanks
Race Director
Joined: Dec 2006
Posts: 10,383
Likes: 4
I have a few questions concerning the hydraulic clutch system on the C4's. I have a 94 coupe, with about 110,000 miles on it, and was wondering what is the average life of the master and slave cylinders, when can you expect some problems? Just wondered if it is wearing out, or slowly losing fluid, if it will show up in shifting problems.?
Also..what's the deal on using hydraulic fluid? I have heard that once you open a bottle of hydraulic fluid, you should use it all, or throw it away, because if you keep it a long time, even though it is sealed, it will tend to get moisture in the fluid. Since this stuff for the clutch isn't cheap....at least not the GM stuff from the dealer, I would hate to throw it out, if its still good. Comments? suggestions? thanks
Also..what's the deal on using hydraulic fluid? I have heard that once you open a bottle of hydraulic fluid, you should use it all, or throw it away, because if you keep it a long time, even though it is sealed, it will tend to get moisture in the fluid. Since this stuff for the clutch isn't cheap....at least not the GM stuff from the dealer, I would hate to throw it out, if its still good. Comments? suggestions? thanks
The hydraulic fluid you should use is simple DOT 3 brake fluid. Yes DOT 4 has a higher boiling point but DOT 3 is less hygroscopic than DOT 4 and the clutch fluid should never get anywhere near hot enough for the boiling point to matter.
I use synthetic DOT 3-4 brake fluid for my brakes and use the exact same stuff in the clutch.
If you replace the master and slave and the hose between you could even go with DOT 5 in the clutch and never worry about water in the fluid. But what I saw on my car and I know it isn't a scientific survey but just what I sw on one car is that the rust from the outside took out the cylinder not water on the inside. I tried to be very careful with the brake fluid and keep it off the painted surface of the cylinders when I replaced them. I know that stuff can cause paint to fail and that leads to the rust and that leads to the dark side...Luke...
Safety Car
Joined: Jan 2006
Posts: 3,566
Likes: 4
From: Mt Laurel NJ
St. Jude Donor '06-'07
You should go here and read about the hydraulic systems on our cars:http://www.zfdoc.com
The least you want to do is change the fluid, but if it were my car, I'd change everything.
Take a look at the fluid in the master, it's under the computer. If the fluid is dark, it needs to be changed. I changed my fluid to the GM stuff two years ago when I replaced everything for the second time in two years, and it is still clear.
Randy
The least you want to do is change the fluid, but if it were my car, I'd change everything.
Take a look at the fluid in the master, it's under the computer. If the fluid is dark, it needs to be changed. I changed my fluid to the GM stuff two years ago when I replaced everything for the second time in two years, and it is still clear.
Randy
Drifting
Joined: Sep 2003
Posts: 1,363
Likes: 7
From: 1994 LT1 Coupe 6-speed with FX3 & 2000 LS1 Vert 6-Speed with F45 Hunterdon County, NJ
http://www.zfdoc.comOn there you will find lots of good info, including a 'test' to determine the health of the clutch hydraulics.
For example, roughly speaking, the life of the slave is 50k and master about 100k. Also, the rubber within the hose between also breaks-down -- but since it is stainless-steel wrapped, it doesn't expand, just adds contaminents to the fluid and worse-case might leak a bit (our 94 was NOT leaking when I replaced it at 95k about 5 yrs ago just because -- as I was doing slave and master and all clutch stuff anyway).
beware there is QA issues with slaves -- NAPA is a good alternative to GM OEM. ALso, DO NOT pressure bleed the slave unless it is fully installed (gravity bleed before install, install, THEN pedal bleed, otherwise damage and subsequent leakage and replacement WILL occur).
RE: the GM clutch-fluid -- in addition to it being a DOT-3, it also has additives to reduce the entrapment of air and reduces squeaking -- both of which are VERY important -- so stay with the GM product, you will not be sorry.
Lastly, since bad hydraulics can hurt the tranny (syncros), if not sure, and have the money, just do it.
ALso, don't forget to change the tranny fluid (roughly every 12k-15k) -- and consider using the BMW 10w60 oil (mentioned in sticky and on zfdoc.com).
Instructor
Joined: Aug 2005
Posts: 112
Likes: 0
From: Lone Tree CO
After a lot of reading of threads I went to the 10w60 BMW for the Trani fluid. I think the previous owner abused the trani and I get a whine in 1 & 2. Hopefuly this will delay the breakdown. I am going to change my clutch fluid to GM as I just checked mine which was normal dot 3 and it was black. I just replaced the master and slave last year and put a new SPEC clutch in last month.
Thread Starter
Pro
Joined: Feb 2003
Posts: 715
Likes: 21
From: Ontario California
Thanks for all the help and advice guys...I'm doing the research on this subject at the moment. The http://www.zfdoc.com site is very good, especially on explaing the clutch system. I'm pretty sure now, my shifting problems are being caused by the clutch hydraulic system's wear and degrading of the components.
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