Wisconsin Joe

I've been planning on flushing my brake fluid. I've got most of it figured out, and the stuff I need lined up.

I'm planning on following Dwayne's writeup on it here:

http://dwaynesgarage.norcal928.org/BrakeFluidFlush.htm

BUT...

Dwayne doesn't mention anything about the clutch.

I think I should do the clutch at the same time. It's the same fluid reservoir, right?

I searched around a bit for anything on flushing the clutch, but all I can find is about bleeding it. I just want to push the old fluid out with new, just like the brakes.

Can I use the power bleeder on the clutch, just like on the brakes?
Anything special I need to know?
Any pitfalls to watch out for?
How much extra fluid, over and above what I'll need for the brakes, should I plan on needing?

Thanks in advance.

syoo8

I just did this. Yes, it is exactly the same as the brakes, shares the same fluid. I used a Motive Power Bleeder, and didn't mess with pumping the clutch. (When I messed with the clutch, the clutch messed with me.)

Anything special to know: if you over pressurize the bleeder when doing the clutch, the blue hose can come undone, and you will be in for a big mess. Keep the Power Bleeder under 10 psi for the clutch.

These are some good threads:

S4 Clutch Just Bleeds Air

Clutch Hydraulic System Bleed: Method #2

Awesome Clutch System Bleeding, Etc., for Dummies

Hope this helps.

Hilton

When you pressurise the reservoir, you're already pressurising the clutch blue hose. So if you pump it up to 25psi for the brakes, you're still running the risk of popping off the blue hose.

I stick some hose clamps on the blue hose when I replace it.. just for peace of mine

dr bob

With patience, the pressure needed for flushing is not that great. 10 PSI is more than plenty. The Motiv bleeder's big duty is keeping the reservoir full. After that, put a section of clear vinyl hose (Home Depot) from the bleeder into a bottle that has enough fluid in it to block air going back, and hang the bottle so it's higher than the caliper. Think plastic pop bottle, with a coat-hanger wire or similar through a couple holes in the neck, so you can dangle the bottle from a spring -WITH NO RISK OF ACCIDENTALLY SPILLING BRAKE FLUID -. Put a smear of silicone grease on each bleeder screw's threads so it doesn't leak fluid out or air in around the threads. Then a little pressure on the reservoir with the power bleeder will slowly push new fluid in to replace the old.

I have a "turkey baster" dedicated to garage duty, and I use it to pull as much old fluid out of the reservoir as possible. Then fill the reservoir with new fluid, then connect the power bleeder cap, then add a little pressure. That means less old fluid to push out, and less mixed fluid to push out too.

A plastic garden trash bag, opened up to a flat sheet, taped with painter's masking tape, covering the whole front fender and tucked in around the MC area, an old bath towel stuffed under the MC area, and a plastic dishpan under each wheel area as you work, maybe with plastic drop cloth to be sure. Brake fluid will damage paint in a short while, so a little precautionary work can save you some tears if there's even a small spill. Brake fluid stains my industrial-strength epoxy workbay floor, in spite of what the manufacturer said about that; "impervious'" means different things to different people I guess.

A couple liters of fluid should be enough.

jon928se

If it's a flush to do a thorough clean of the internals, consider buying 2 litres of cheap DoT 3 fluid to use as a Cleaner, then bleed through with high quality ATE or similar.

dr bob

The only ATE we are 'allowed' to buy in the US these days is the gold, which looks amazingly like tired/wet/rusty standard fluid. In the US, synthetic Valvoline-branded DOT-4 is only a couple dollars/liter more than generic DOT-3 anyway, so pushing a couple liters of that through the whole system is less than $20. Hard to justify using generic/cheap DOT-3 even for just an intermediate flush step, in my opinion anyway.

We hosted a clinic day a few years ago, and one of the guests brought half a dozen 12oz bottles of "DOT-3/4" fluid from a local discount place. I had grabbed a case of good DOT-4 liters in anticipation. Still have the little bottles in the drawer, mostly because I can't see using it in anything I drive these days. Maybe I'm too picky, since the other cars generally need just DOT-3 anyway, and this stuff is functionally free at this point. K has her Toyota 4Runner serviced at the local dealer religiously, and they sort of laughed when I suggested that the brake fluid should be flushed regularly. Secretly, the trans, transfer case and differential oils get swapped regulary, along with coolant and power steering fluid. The service tech finally asked one day why the blue Toyota power steering fluid had turned pink. Only took him a few years of looking through the reservoir to notice. So maybe the 4Runner will get the generic DOT-3 next time.

linderpat

great info here. Keeper.

z driver 88t

+1 on the Valvoline DOT 4 synthetic. Was adequate for mild track days and autocrossing. Cool advice on the silicone grease at the bleeder threads. I always wondered how to keep air from blowing past those threads.

antsmands

I used my Motive at 15psi and bled brakes and clutch at the same time with DOT 4. Took a little more work to get all of the air out of the clutch line as I had remove the clutch master cylinder but worked fine.

Wisconsin Joe

Thanks to everyone who offered suggestions and advice.

I did it today, and it went very well.

It worked out somewhat differently than I had planned.

The "Power Bleeder" that I borrowed was NOT a Motive style pressure bleeder. It was a Mac VP5000K, which is basically a Mighty-Vac with a few extra attachments. It included a catch bottle just ahead of the pump, hose to go to the caliper/slave cylinder and a rubber boot sort of thing that went over the bleeder. It also had an adapter for the brake fluid bottle that allowed me to put the bottle into the reservoir and it would maintain the level without spilling. It's a nifty little "doodad."
Instead of pushing the fluid through the reservoir and master and out the bleeders, I pulled it out the bleeders. It made any concerns about overpressure blowing off the blue hose disappear.

I broke the bleeders loose, then coated them with silicone brake grease. I put the boot on and built up a vacuum. Once I loosened the bleeder and got the fluid flowing, I pushed the boot all the way down onto the bleeder to the base. Being all the way down, the brake grease gave a really good seal and all the bubbles stopped.
I pulled a good bit of fluid through the first one. The color didn't change much, it turned out I was probably using the same stuff that was already in there. But I could see enough of a difference that I was pretty sure I had all the old stuff out of the reservoir. I did both sides in back, then the clutch.
I deliberately pulled extra through the clutch, making sure I flushed the master out well.
Both fronts went fast, I now knew what I was looking for with the subtle color change, and it really didn't take much. Both fronts together was less than the first back.

It took a full quart, plus a little less than half of the second one. I probably could have used less, but I used Valvoline synthetic 3/4, and at $8 a quart, I cared more about getting it flushed thoroughly than how much fluid I used (It's cheaper than the oil ).

So all in all, a good afternoon spent. We got about 6" of snow today, and being able to get something done on the car made having to endure another snowstorm a little bit easier.

Thanks again for all the knowledge that you guys are willing to share.

gcthree

I used the Motive power unit because my systems were completely empty after a system rebuild. HOWEVER, I do have a unit I bought at Harbor Freight that uses compressed air to create a vacuum and sucks the fluid through the system without the need to pressurizes the master cylinder.

I replaced the rubber hose on our RX8 with a steel braided unit, and the only way I could get a pedal was by using the HF unit. I intend to use it going forward on the 928.

Bob

dr bob

Bob,

When I replaced the hoses on my car, I used a combination of a vacuum bleeder and my home-built pressure bleeder. It was the only way to get ALL the air out of all the high spots.

Can you post info on the vacuum bleeder you used? I cobbled mine together with shop scraps, including a venturi pump I had from a long-ago project.

gcthree

Sure, Bob.

This unit is $26 at Harbor Freight and includes a vacuum unit with trigger to control the suction and a fill-bottle with a group of adaptors that allows the reservoir to auto-fill as you bleed. I tried every method to bleed that RX8 clutch line with zero success. The vacuum bleeder worked perfectly, and I continued onto the brake circuits with equal success.

Best part is that you are not pressurizing any of the components in the system, especially important for us 928'ers as we side-step the potential blow-off of the blue feed hose when we pressurize the master cylinder. It also provides a constant source of high vacuum as opposed to what you get with the MightyVac, for example (which has never worked for me...).

Again, with a completely empty brake and clutch circuit after my rebuild, I felt that I needed the pressure system to fill the circuits, but now filled, I'll use the vacuum bleeder for flushing.

Here's the link and a photo.

http://www.harborfreight.com/brake-f...der-92924.html