MMI

So I proceeded to bleed my own brakes using the basic 2 person method. I followed the sequence of rear right, rear left, front right then front left. The rears went fine but on the front right was seeing a lot of very small air bubbles like the size of fine sand. Didnt see this on the rears. They kept coming steady so I kept on pumping the brake pedal. Then I accidentally let the level drop too low in the reservoir and I heard it suck air! So now what. I know it's best to start over if that happens but I didnt have enough fluid left to do that so I kept going with the front right, got rid of large air bubbles but the small barely visible ones never stopped. So moved on to front left and same small bubbles were present and also couldn't bleed them all out. In all I used up 3 bottles! On test drive the brakes felt good even at repeated high speed hard braking. So i need advice, are the small air bubbles normal? Do I need to redo the whole process because I allowed air in while bleeding the 3rd caliper? Thanks in advance!

M4rk

Q: Are the small air bubbles normal?
A: Absolutely not. Unless the hose you attached wasn't sealed on the bleeder nipple well, causing air to suck in. In any case, introducing any air to the master cylinder requires a different procedure for a complete bleed. I haven't studied it, but suspect it may require TechStream to engage the ABS pump.

lobuxracer

iTrader: (2)

It's called cavitation from not opening the bleed screw far enough. AMHIK. You should open at least a half turn, preferably a full turn after putting some (not a lot of) pressure on the brake pedal. Cavitation creates bubbles like you describe in any liquid passing through a restriction. The valves in your heart will typically cavitate your blood at 235 bpm and kill you. I only know this because I have an unusually high maximum pulse rate (stress tested to 206 at 37 years old). Hyraulic systems are carefully designed to avoid cavitation as it takes quite a while to get the air out of hydraulic fluid.

MMI

What you're saying makes sense. I did find that the front bleeder screws were looser than the rears and tended to want to close back up because of the twist in the bleeder hose. I had to reopen them a few times. What a PITA. so yeah they were probably barely open most of the time. Having said that, if the small bubbles were being introduced at the bleeder screws then I would think that they would have been expelled into the bleeder hose and not getting sucked back up the line. I did make sure the pedal was kept down on the last pump as I closed the valve. So I guess that should be ok? I'm just still concerned if I caused any harm by letting a bit of air suck in through the reservoir or am I good.

M4rk

Learned something new today. But I am not sure if it is safe to assume this is the root cause when OP states he let the MC run dry.

MMI

Just to clarify, I was seeing the small bubbles many pumps before the MC reservoir sucked air. So that leads me to believe the air sucking in from the MC was not the cause of the small bubbles. However after air got in through the MC there were a lot of large bubbles that I managed to bleed out, but the small ones stayed constant. So that seems to support lobuxracer's opinion.

lobuxracer

iTrader: (2)

Not an opinion. My experience on many cars and motorcycles. This is why I use Earl's Solobleeders. Never have cavitation (which actually isn't a problem to worry about, because it happens as the fluid crosses the seal for the bleeder), and I can do the job all by myself.

Also from a long time ago: https://www.clublexus.com/forums/is-...l#post10537248

MMI

Thanks for the free education..always appreciated.