Brake Bleeding Blues

[Robert Coats]

No Porsche content, so Off Topic, but still automotive.

2017 Acura RDX (5-seat version of the larger MDX)...time for front brakes and rotors after 48k miles. Done this job many times on other vehicles, and the RDX's calipers, rotors, anti-squeal springs/shims, etc. all quite straightforward. No drama fitting new OEM parts.

In the past, my little slice of lasagna was always able to pump the pedal on other cars while I turned the bleed screws, but decided to get a fancy air-powered vac system:



It worked great sucking the master cylinder empty, and with a fresh fill, I attached the fitting to left side front brake bleed screw. Started the vac, opened the screw, and voila! Great gobs of brownish fluid and bubbles. Watched the master cylinder level, topped off a few times, and after nearly 10 minutes, got clear fluid flowing, but LOTS of bubbles still in the line?!?!?

Tried 'barely' opening the bleed screw, but did not see any change except slower flow. I could simply not seem to clear all the air out of the line, and suspect it might have been drawn in from the bleed screw threads?

Got Mrs. Robert out there for the old reliable pedal pump & hold drill, and no more bubbles. Brakes road tested great.

What did I do wrong? Wondering if there is a slightly different procedure to properly bleed air from the system; it does have ABS...

I will reach out to the MityVac support, but thought I'd ask here as well. Thanks in advance for any tips.

[David Inc.]

I've used a mityvac for years, and that was most likely air leakage around the bleed screw threads. I always use that first then do final bleed with an assistant at the pedal.

It feels like it really only works well for getting the majority of the fluid out--I've never been able to get a fully firm pedal without doing final bleeding from the brake pedal pedal.

[LEAKYSEALS951]

I had the same problem with the HF version of the same system.

Assuming it was air getting sucked in though the sides/threads of the bleed screws, I placed the suction tube going straight up from the bleed screws (for example, threading the bleed tube through the front coil spring to hold it vertically above the bleed screw without me having to hold it), turned off suction, and let the fluid fill the tube above the bleed screw. The bubbles stopped, and the vertical clear tube filled with pure brake fluid (similar to watching a carbonated beverage 'settle' when you pour it too fast into a cup). Tightened the bleed screw, and success.

EDIT- as long as the master cylinder reservoir stays pretty full, no air should have gotten into the ABS system, so don't worry about that quite yet.

Good luck

[SCadaddle]

In the past I've used the 2 person "talk to me" pedal bleeding system, then the mighty vac, then the Motive power bleeder, and finally this last time when putting new kits in the calipers of my SC I went simply with gravity bleeding followed by quickly swapping out the original bleed screws with speed bleeders and using my foot on the pedal. The speed bleeders are the ticket. And yes the speed bleeders do use a dried thread sealant to make a seal when loosened in the caliper.

[cockerpunk]

i never use the vacuum bleeding.

just use a water bottle and tube. tube in the bottle, brake fluid above the tube line, tube up to the nipple, open the nipple and pump the petal 10ish times.

real easy. one person.

[BK911]

Not a fan of vac bleeding for the reason you described.
You can try to put grease on the fittings, which should help a little.
Pressure bleeding is the shizzle.
I made a fitting for under $5 and used on MANY vehicles.

[nota]

did you actually dry the master at first ?

sometimes that needs a bench bleed of the master to get the air out

I once got a car very cheap because the brakes would not bleed and stayed soft
as nobody bench bleed the master first just tryed the normal wheel and even air vac was tryed

if the air is up hi in the master it never will all get out without the hi volume short run of bench bleeding [ie short loop master in to the res direct pump til no bubbles]

[mattdavis11]

I'm going to try a new to me method today. I need to bleed the clutch master & slave on the 944. I'm going to use my compressor, flush bottle (canister with straw) with air gun, and a rubber hose attached to the slave bleed nipple and push the fluid up to the reservoir.

[John Rogers]

Hummmm, any type of bleeding I ever did when I had my vintage race car, my daughter's 914 2L and my wife's 1987 930 were performed with a pressure bleeder. I used about 5# of pressure and switched between clear fluid and blue fluid (don't remember the brand) but I still have a couple bottles of the blue stuff as I bought a whole case of it, 24 quarts I think and they have lasted about 22 or 23 years. I used a tall hard plastic drink glass from Disney Land to catch the fluid from the bleed screws.
John

[dw1]

After many issue with vacuum bleeding brakes I switched to pressure bleeding using the kit from Motive Products (widely available, including by Pelican) and have been extremely satisfied.

[Bill Douglas]

Speed bleeders.

[Alan A]

Some ABS systems need to be switched into a special mode through the ECU to bleed them fully.

We removed the system on my Triumph (long story - mixed GM setup) because it was almost impossible to get it to cycle correctly. Check this isn’t the same.

[Robert Coats]

I'm quite sure now the air issue was due to the bleed screws, and it makes more sense to pressure bleed vs. vacuum bleed.

Many thanks again to the Pelican Brain Trust for their rapid and informative help!

[drkshdw]

Originally Posted by cockerpunk

i never use the vacuum bleeding.

just use a water bottle and tube. tube in the bottle, brake fluid above the tube line, tube up to the nipple, open the nipple and pump the petal 10ish times.

real easy. one person.

After trying Motive, DIY garden sprayer and speed bleeders, this ^^^ is how I do it now. It is so simple and works every time. No need to inconvenience anyone but myself and it takes 10 minutes to do all 4 corners. It's never failed me.

[rusnak]

The Motive bleeder will get you there, but not past the 928 style brake proportioning valve if you're bleeding a G-series 911. Depending on how "dry" the system got, you may still need a 2-person bleed, only to open up the proportioning valve with leg pressure.

I never understood how to bench bleed a master cylinder the right way. The damn fluid always leaks out on me, and then I make a mess and wonder why I even did that. And on the Cayman with all of the brake servo lines, I'm hesitant to even try to change out the MC for a larger one. All of those dang little lines look like too much work to bleed.

[GH85Carrera]

The only brakes I have ever bled were my 74 914, the 85 911 and my El Camino.

I sold the 914 26 years ago so it is not fresh in memory, but it was easy, 100% manual system. My 911 gets a brake fluid change every single spring, no exceptions. The mater cylinder has never been replaced or had any issues.

I have a vacuum bleeder, a hand operated small one that needs frequent dumping of the little catch can. I bought a much bigger vacuum pump and it holds over a gallon, so no issues of it filling up.

I always see bubbles, and I always assumed it was from the bleed screw to the vacuum hose connection. I always get a nice firm pedal, so the bubbles don't ever bother me. My El Camino power brake and master cylinder developed an air leak about a year ago, so the original was only good for 35 years, and 370,00 miles. I change the brake fluid on the Elky every third year.

Bleeding the brake drums in the rear is a rear pain in the butt, as the bleed screw is almost hidden up inside the drum housing. That is a big reason I am less proactive about the bleeding. No way to get the vacuum hose or any hose on it, so it just makes a mess on the floor, that I have to clean up. I use a metal catch pan and a oil drain pan that gets most of it, the metal drip pan gets the rest. It is still a mess.

I would suggest you just ignore the bubbles, and go by pedal feel as to getting the air out of the system.

[svandamme]

just a tube that fits snug over the nipple.
route it upwards so the air bubbels go away from the nipple.

open the nipple
go pump the pedal till you get a foot worth of fluid above the nipple
close the niple
DONE

There is no easier way
There is no cheaper way