Stock brake system capacity Options

[-JR-]

Anyone have any clue, idea, guestimate of how much fluid a stock 914/4 brake system holds?

I'm putting in DOT5 fluid on my next brake flush this week and want to make sure I have enough. It's pretty pricey stuff, so I don't want to go overboard.

I've got 700mL now... Hoping that's enough.

Thanks!

[Dave_Darling]

For a complete flush, I use a 1-liter bottle. Sometimes a bit more, just to make sure the old stuff is out.

--DD

[Cap'n Krusty]

"DOT 5"? If it's the "real" DOT5, I suggest you do some SERIOUS rethinking. First off, replace EVERY bit of rubber in the system and flush the system until there's absolutely NO remaining conventional fluid. Next, be prepared to spend HOURS bleeding the system. Or maybe days. Then sit back and relax, secure in the knowledge that returning the system to conventional fluid will be even more difficult and expensive.

The Cap'n

[Eric_Shea]

(IMG:style_emoticons/default/agree.gif) do NOT use DOT 5.0. I've seen issues that I call "caliper worms" when the fluids mix and I've heard good arguments that our seals are not meant for it.

Yes, someone will chime in that they put it in their pickemup truck and they get a better pedal. They now use it in all their cars and they've had no problems and we're all insane but, as the Cap'n suggests, DO NOT mix the fluids.

These worms are hardened fluid that gels in the lines when mixed and, through the force of the master cylinder, this "paste" gets pushed into the caliper bores. 914 rear calipers have very intricate mechanisms inside the pistons and these caliper worms can gum up the mix.

Use 4.0 or 5.1 fluids. ATE or Castrol are some of the best.

[-JR-]

Well took 3 hours and 1.5 liters of alcohol to flush and another hour of bleeding, but it's all done now.

My best guess on the amount of fluid a stock 914 brake system can hold is 500mL. So if you are using brake fluid to flush out old brake fluid, you will certainly want at least a liter. Maybe more if you are flushing a system that hasn't been done in a while.

I used all 700mL of brake fluid because I ran extra fluid out to search for more air bubbles in the lines.

I've run DOT5 in other cars that were even older and never had an issue. The only thing I will say is that DOT5 seems to be a little softer pedal, on the whole, than DOT3 or 4. I suspect it's because of the silicon based formula lubricating the surfaces better, but I've never done any in depth research.

[Cap'n Krusty]

Well took 3 hours and 1.5 liters of alcohol to flush and another hour of bleeding, but it's all done now.

My best guess on the amount of fluid a stock 914 brake system can hold is 500mL. So if you are using brake fluid to flush out old brake fluid, you will certainly want at least a liter. Maybe more if you are flushing a system that hasn't been done in a while.

I used all 700mL of brake fluid because I ran extra fluid out to search for more air bubbles in the lines.

I've run DOT5 in other cars that were even older and never had an issue. The only thing I will say is that DOT5 seems to be a little softer pedal, on the whole, than DOT3 or 4. I suspect it's because of the silicon based formula lubricating the surfaces better, but I've never done any in depth research.

It's because it retains air in suspension, not because it's "lubricating the surfaces better". One of the downsides.

The Cap'n