MFrunkerOG
Active Member
Yep have the MPP cylinder brace as well. Yes I went with UP braided lines.I've never seen that with a pressure system unless you were using too high of a psi when pumping it up. It happens to me every time because I prefer using a vacuum pump.
When doing mine the other day, I went through 2L, which is too much, but wanted to make sure that trash fluid was 100% gone.
Did you do braided lines, or just a fluid change? You may want to grab one of those master cylinder braces as well. It gets rid of that initial pedal slop and bites as soon as you touch it.
As for using too high pressure, I was using 15psi. But I have a feeling that the reason it only happens on the rears is because the pressure actually reduces in the lines due to line resistance.
It’s sort of like a beer line calculation (those who homebrew and keg know). A 1/4” steel beer line has an active line resistance of 1.2lbs per foot. That means if you apply 1.2psi at the inlet of a 1ft pipe of 1/4” diameter, the line resistance will cause 0psi at the outlet. Fluid will still flow, but at no pressure.
Now while replacing the car’s brake lines with the braided ones, I saw the feeder steel lines being much much smaller in diameter - almost 1/8”. I suspect the line length of the feeder lines at the farthest corner (rears) is probably a good 8 feet of line. The line resistance is also exponential with decreasing diameter - i suspect at least 3lbs per ft. So 24psi is the loss on the farthest corner. Neglect the 1psi of pressure added due to gravity for this explanation.
So essentially, bleeding at anything less than 24psi on the farthest corner from the reservoir means a Venturi effect is going to happen as there is no positive pressure left at the bleed valve.
I think this is why Tesla recommends 30spi on the bleeder pressure as you need to overcome that line resistance on the farthest corner, and still have a few psi at the bleeder valve.
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