Clutch Master Cylinder Fluid Replacement

[Silverfox1]

I just got thru replacing the fluid on my '96 LT4 using a turkey baster to suck out all the old stuff & refilled with Prestone Dot 4. It has 17,000mi & was dark brown.
My question: same method for the ZR-1? I don't want to get this started & find out there's a ZR-1 specific wrinkle which I can't handle. I have 23k on it & everything works & sounds fine in that dept. The service records do not indicate the fluid was ever replaced.

The brake fluid is pretty dirty, but I think a proper bleed is the best solution. Have never done one, so think best to take it in.

I also suspect the pads are original & I did have to hit brakes hard once & was not impressed, so thinking about replacing anyway. I've seen so much about pad brands, it makes my head spin. I may at some point take it on a track day, but otherwise, it's really just city/highway miles.

Thx for the help!

[Paul Workman]

I believe the brake slave/master are the same on a ZR-1 as your 96. But, in any case there is a bleeder valve on the slave cylinder.

One method of changing the fluid is to -

1. replace the fluid in the reservoir with new fluid,
2. and then pump the clutch about 50 times
3. and then again replace the fluid in the reservoir.
4. repeat steps 1 thru 3 until the fluid in the reservoir remain relatively clear after the 50 cycles.

Another (I prefer) method requires jacking up the front of the car to access the slave cylinder and use the slave as a "pump" to pull fresh fluid into it from the reservoir. (I usually try to combine tasks e.g., changing trans fluid, etc to reduce the jacking up the car/jack stands process as much as possible.)

In short, I start by replacing the fluid in the reservoir (and if you have a method of keeping the reservoir full of fresh fluid - such as an attachable Mitivac bleeder kit, or an assistant to keep the reservoir filled, the process will go very quickly w/o you having to climb out from under the car to keep filling the reservoir...just sayin!)

I remove the slave from the housing
loosen the bleeder valve (and I attach a clear plastic tube to the bleeder so the dirty fluid runs into an oil catch can)
force the clutch actuator rod back into the slave cylinder and HOLD it while you close the bleeder valve.
Then release the actuator rod and let spring tension force the (internal) piston outward - drawing fresh fluid from the master reservoir into the slave cylinder.
Then, loosen the bleeder valve again and repeat the process a few more times until the expelled fluid is clear (mine usually takes no more than 3 cycles to flush the entire system before the fluid 'runs clear'). The whole pumping process only takes a couple minutes, and ALL the old fluid and air is removed - is why I prefer this method.

If you don't have a tool (like the Mitivac) to automatically keep the fresh fluid filling the master reservoir, then a trusted assistant needs to be ready with more fluid to keep from pulling air into the system - very much like the process for bleeding brakes, doanchaknow... OR, be ready to scoot out from under the car to fill the reservoir yourself, and then get back under the car to "assume the position" for another cycling of the slave cylinder. Prolly not a big deal if you're skinny and spry like Marc Haibeck, but old FAT guys (like "SOME" of us...) might rather to not have to get up and down and up and down so much. (Just sayin...)

AS FOR BRAKE PADS:

For me, ±98% of my driving driving is normal street/highway, with occasional sprints through some twisty mountain curves or zips down the 1/4 mile track. For that I find the Hawk HPS pads to require less pedal force overall than stock pads or some others, and I like 'um very much. Even for a limited amount of track/autobahn type running around, the Hawk HPS pads work quite well, I find.

That said, serious autobahn track drivers often opt to use dedicated (racing) pads for the track, and then change back to "street pads" for the drive home. (the C4 Corvette calipers are quite well designed to enable quick pad change out, I find.)

Note: I don't "HPDE" competition race (yet), so suggestions for true racing pads will have to come from someone that does - like Mark Horner (for one).

[garyhugo]

Whats with the black rubber cup in the resevoir?

[BigJohn]

Originally Posted by garyhugo

Whats with the black rubber cup in the resevoir?

That's funny!!!

[Silverfox1]

hey Paul,
Thhatnls for the response. I like alt #1 on the clutch fluid. Worked fine on the '96. I'll check out the Hawks, have seen word on them before as well. Rob

[alwayscode390]

Originally Posted by garyhugo

Whats with the black rubber cup in the resevoir?

Im not going to lie, I've wondered that myself HAHAH.

I tried searching but only came up with this thread.

I have fell victim to filling up the resevoir to full, and pushing the black rubber boot back into it while 1/2 the fluid comes out LOL. That boot goes almost to the bottom of the resevoir cup.

Are you just supposed to fill it slightly, and push the boot in ... then see if it hits the full mark?

Thanks ---

[garyhugo]

I saw a post on CF from many years ago and they were confused as well. It seems that putting just enough fluid in to raise the level to full when the cup is installed is the proper way.

[alwayscode390]

Originally Posted by garyhugo

I saw a post on CF from many years ago and they were confused as well. It seems that putting just enough fluid in to raise the level to full when the cup is installed is the proper way.

OK, thanks Gary, thats what I ended up doing the other day ... luckily I had a siphon and could take fluid out as needed to get it full to the top without it spilling out HAHAH ---

[Roadster]

Originally Posted by garyhugo

Whats with the black rubber cup in the resevoir?

As I understand it, the black rubber cup is a vapor barrier. Its purpose is to keep air and moisture from entering or collecting in the reservoir.

[BigJohn]

Originally Posted by garyhugo

Whats with the black rubber cup in the resevoir?

Is this what you are talking about?