Reverse Brake Bleed, Anyone, Anyone?

[DRACO A5OG]

OK guys, I was searching for videos of how to adjust valves and found a couple of videos with VAS tool which I have, pretty cool then I stumbled on to something very interesting and it could apply to our brakes but certainly the G50 with the brake fluid being shared by both the brake and clutch.

Has anyone tried the REVERSE Brake Bleed to get all the air out of their system?

I am tempted to try this. I recently rebuilt my calipers but I still have soft pedal and need to pump several times before it will bite at the upper pedal travel. When she is off, she bites at the upper pedal travel but once on she will get soft.

Here is the Video: ‪BMW, VW, Porsche Clutch Bleeding‬‏ - YouTube

It make total sense to me to chase the air up the line to the reservoir instead of pushing it down hill

Jim

[rusnak]

Once the pads make contact with the rotors, how does the pedal feel? Firm, or still spongy? One is the pistons needing to be pushed out more, and the other is brake bleeding. If you need to get more air out, then pedal bleeding will still be your best hope. I can tell you what works for me.

[DRACO A5OG]

When she is off, very firm and at almost top of the pedal travel however when I turn her on she drops but bites the rotor. After several pump she is firm again.

I plan on bleeding her tomorrow after I pick up some more fluid, drove her all day to try to move the air. It got a little better and she bites evenly and smoothly, just have to pump, even if I don't pump, around the end she will bite and stop firmly.

Jim

[rusnak]

I wonder if the brake pistons are just retracted too far? I'd try extending them by tapping the pedal without pads, then re-install pads and use a brake pad spreader. You have to re-install the calipers several times.

One word of caution: the little hard brake line is easy to bend. One small kink in that brake line will drastically reduce fluid flow. Someone should make an improved part for this.

[DRACO A5OG]

I don't think they are, I watch the travel of the pistons and after pressing the brake they retract about 0.5MM as designed I assume with those springs/clips attached. I will check again tomorrow and try your method of letting them out with piece of wood in between them to push out right before they pop out.

Yes, I went thru the ordeal with my front hard lines, one twisted off and the side snapped. I went to Napa and purchased a straight 8" M10-1.0 pitch bubble end hard line, a perfect fitment but a bit too long, so I went to Home Depot and purchased two 1" sliding door brass rollers.

I screwed the rollers on some wooden block and positioned them diagnoly. Basicaly made a mini pipe bending tool and made and "S" bend and to match the fitment postion perfectly. VOILA new copper with soft steel shroud covered in polymer, design to bend and flex with out compromising the tube's integrety. One of the Best $5.00 spent.

[schumicat]

I have seen people comment the reverse bleed is a bad idea because it can send any loose corrosion in the calipers up into the m/c, instead of being forced out with a regular bleed. I once had a problem with a hydraulic clutch (mk1 MR2) where it was impossible to get the air out with vacuum or 2 man bleeding method. I then used a pressure bleeder (pressuring the m/c) and the problem was instantly solved. I would try pressure bleed before the reverse bleeder. you can make one out of a yard sprayer.

[wildcat077]

+ 1 for the pressure bleeder as well,i wouldn't chance it any other way.When i did my brake upgrade i replaced the 4 calipers,installed a new 23 mm master,fabricated 4 new hard lines because the originals were too short,replaced the soft lines with stainless lines and flushed and bled the whole system including the clutch slave cylinder.

The Motive bleeder was a charm and i didn't need anybody pressing on the brake pedal as my 17 year old son would have whined and complained and it probably would have cost me a pizza ... lol
Got the Motive universal adaptor and flushed my F150 and my son's Honda Civic just as easily!

Cheers !
Phil

[dad911]

I've always had good results with pressure bleeding.

I wouldn't reverse bleed brakes, especially on a track car, or an older car with old fluid. I want to get the crappy fluid out of the caliper, not push it back into the system.

[DRACO A5OG]

Ah so desu ne >-), now that makes very good sense, I can totally see that.

Debris into the MC, OK, I rather have moisture then debris into the MC.

Luckily I made a pressure bleeder from HD with gauge about 2 years ago, tested fine but what I did notice was the compression of the air creates vapors i.e. moisture to be possibly introduced into the system. The filtered pressure bleeders are extremely expensive.

OK, will try it if one more 2 man bleed does not work.

But for my buddies G50 Trans, he may need to use the Reverse Bleed to get the air out of his clutch pedal.

Thanks fellas I love this Board!!! You guys Rock!

Jim

P.S. when I rebuilt my calipers, I found old fluid coming out of the piston receivers. :eek; I know this because it was blue, after 2 flush with gold.

[dad911]

Originally Posted by DRACO A5OG

.....
Luckily I made a pressure bleeder from HD with gauge about 2 years ago, tested fine but what I did notice was the compression of the air creates vapors i.e. moisture to be possibly introduced into the system. The filtered pressure bleeders are extremely expensive......

I use my compressor with a second regulator (under 10# pressure) and an air line filter/water separator) (had this for spraying paint)

Something like this, but cheaper from harbor freight: Amazon.com: DeVILBISS AIR LINE FILTER/Water/Oil Trap w/50 Foot HOSE: Home Improvement

But pumping up air with a yard sprayer/motive should not introduce much moisture, the pressure is much lower than an air compressor.

MC is open to air anyway through the vent.

[DRACO A5OG]

Ah ha! Thanks Dad

I am totally convinced, will do the pressure bleed today and report

Your other son from another Mom and Pop

Jim

[PabloX]

That sounds like it's purely a technique for diagnosing a leak and/or a technique for bleeding a hydraulic clutch only.

[DRACO A5OG]

Well, for a hydraulic clutch it would make sense because on the G50 even though it shares the brake fluid it is seperate from the brake line system.

But for brake pushing up debris from the calipers is not a wise idea.

Pressure bleed it is!

[rusnak]

Draco, I have had the Motive power bleeder for about 10 years. 50% of the time it works fine, but after a caliper rebuild, the thing just would not get all of the air out.

Here's what I did, and I'll get flamed for posting this but so what, I don't care.

Get some clear refrigerator hose that fits the bleeder. I think it's 1/4". Cut a few feet of hose, and put one end in some old fluid, and the other on the bleeder after fitting a 9mm box wrench on the bleeder. Have a helper pump the pedal until it's firm. Maybe 10 pumps, and hold it down hard. I mean stand on the pedal like a panic stop. Quickly, as fast as you can, open and shut the bleeder. All sorts of air filled fluid will shoot out. Instruct the helper to NOT LET THE PEDAL GO TO THE FLOOR, or you'll end up ruining the master cylinder seals. Repead several times until the pedal is noticably firmer. Repeat with each wheel. There will be no air in the brake fluid. The air bubbles will not stand a chance of staying in there.

[DRACO A5OG]

Well Doc R, You have not steered me wrong, bring on the FLAME, FLAME ON!

Hell, I just got a new can of fluid to do tonight, will update.

10 pumps, press like my life depended on it and quick release and close, not letting the pedal drop to the floor. COPY THAT!

[rnln]

Rusnak, that's called the old famous pedal pumping method . I always use that but Draco likes to try new way.

[DRACO A5OG]

Can I put a block of wood behind the pedal to insure my helper does not drop to the floor?

[DRACO A5OG]

JKD, I love you :

Originally Posted by rnln

Rusnak, that's called the old famous pedal pumping method . I always use that but Draco likes to try new way.

DIE YOU BA$TURD! DIE!!! I just threw out your caliper rebuild kit and pressure bleeder :mad

[rnln]

Then you'll see what I'll do to your 911 and your garage tonight.

Wood block: you have to. No one can stop their foot in the middle of the air with that speed.

[rusnak]

Oh yeah? They don't call him Little Dragon for nothing you know. If that doesn't work then I'll send you my Motive bleeder.