C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Flush Clutch Fluid in my 89?

Old 04-11-2019, 05:12 PM
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Default Flush Clutch Fluid in my 89?

Hey guys, so the only thing left on my Vette that has not been touched is my hydraulic Clutch fluid. My car has 31,500 miles on it and of course has the ZF 6-speed. Shifts and drives perfectly. I did open up the master cylinder reservoir and it is full. Fluid looks good. I stuck a Popsicle stick down into it and just got a little swirl of darker fluid on the bottom of the reservoir. The master cylinder itself is a little rusty looking. I am almost afraid to mess with it since everything is working fine. Do I want to flush the clutch fluid or leave it alone? If I do flush it should I just replace the master cylinder since it is 30yrs old? Any input would be appreciated.
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Old 04-11-2019, 06:08 PM
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Fresh fluids are always a good idea. I am surprised that your fluid looks as good as you describe, considering the age of the system. But then, how long have you owned the car? Do you have any documentation stating if/when the clutch hydraulic system was serviced? If your fluid is still clear or mostly clear, and you recently acquired the car, I would guess that the previous owner has serviced it.

I would suck all the fluid out with a turkey baster or other siphoning method, definitely avoiding any spills on the paint. Then take a clean rag and wipe the sediment from the bottom of the reservoir. Refill with clean fluid and bleed the system through a few times, keeping a very close eye on the reservoir and topping it off -- it is small and quickly goes empty. Most people use DOT 3/4 brake fluid in their clutches but I've heard of some using power steering fluid or transmission fluid as as substitute. I suggest DOT 3/4 brake fluid.
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Old 04-14-2019, 04:09 PM
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Originally Posted by DGXR View Post
Most people use DOT 3/4 brake fluid in their clutches but I've heard of some using power steering fluid or transmission fluid as as substitute. I suggest DOT 3/4 brake fluid.
Dot 5 silicon based brake fluid; it won't attack paint, it preserves seals and doesn't attract and absorb moisture. I use it in my system; I'd use it in the brake system too except that it's too viscous for an ABS system; I use it in all non ABS brake systems.
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Old 04-14-2019, 05:40 PM
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My '89's clutch calls for Dot 3 fluid right on the reservoir cap.
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