Flushing Dot 5 silicone from brake system

[eaton]

The prior owner of my car worried more about paint than pedal feel. So he used DOT 5 silicone fluid. I'm thinking I'll flush and replace with ATE. Any tips on how to completely flush the system? Can I gravity bleed all the silicone stuff out, or is there more that needs to be done?

I've heard the pedal feel improve. Since it's my first Porsche, I have nothing to compare the current pedal to. It actually feels pretty good to be, although I've been in shakedown mode, so I haven't done any hard driving.

Thanks for any tips, Joe

[RSTarga]

That stuff is really bad. It will probably take a few flushes. Use a power bleeder to completely flush, then drive it awhile and do it again. The pedal should feel rock hard when done properly.
I used it in a rarely driven car once. Silicone fluid does not absorb condensation so it formed pockets in parts of the system and rusted some of the components. I had to completely dismantle and rebuild with new seals.

[Jetjok]

I'm wondering if you can really get all the silicone out of the brake system, regardless of the number of times you flush and fill with regular fluid? Thoughts?

[jpnovak]

Completely drain the system by opening the lowest connection on each corner. Blow through with compressed air. Rinse through with isopropyl alcohol (IPA). Blow through with air. Let dry completely. Then refill with new fluid.

btw, I would also recommend pulling the calipers, removing the pistons and flushing them with IPA to get rid of the silicone fluid. The two types are not really compatible.

Yes, its a lot of work but certainly not difficult.

[eaton]

Thanks for the tips. Sounds like quite a job.

[csbush]

It's not that bad, and you get to really go through your brake system and calipers. Make sure your pistons are not rusty, put in some new seals, clips, and pads if needed. Check your flexible brake lines, etc. All good maintenance and a good idea if the car is new to you. Could easily do it in a weekend unless you ran into problems. Will give you peace of mind that your brakes are in good shape.

[66S]

I mixed the two fluids in my old VW bus, with front discs, with no bad effects. Not recommended though. Silicone fluid has more viscosity and air bubbles are harder to get rid of. Tapping the parts during bleeding helps. It is most suited for drum brakes. Not bad just not ideal for discs. If the calipers were recently rebuilt your soft pedal could be from new seals.

[eaton]

That's the thing -- the pedal isn't what I'd call soft. Still should probably make the switch. Probably a good time to convert to a dual circuit master cylinder while I'm at it. Never ends, right?

[csbush]

The fact that it never ends is part of the fun

[Tom F.]

I had to take apart my brakes, completely, put in a new master cylinder and replace the pistons in my S calipers to cure my car of silicone fluid.