Brake fluid went "dry" when bleeding brakes on G8

[xBa380]

Hey everyone,

I am doing brake work on my brothers G8 GT replacing rotors/pads/fluid. I was working on the rear passenger side brake and was bleeding the fluid. I generally am very good at making sure the fluid is topped as I bleed the brakes, but at one point it my helper noted the brake pedal felt off. I discovered the fluid reservoir was likely dry and induced air into the master cylinder.

I topped the reservoir off (and made sure to top more frequently so it would not happen again) and eventually the air bubbles start coming thru the lines. I kept bleeding until the fluid no longer had bubbles (probably much more than I needed, but I wanted to be sure). Once I was sure I got it all out, I went over and did the drivers rear side. Halfway thru my bleed I saw a very small amount of bubbles but it went away very quickly and the fluid change went fine.

I am going to complete the fronts today and bleed those... The pedal feel appears to be normal at this point, firm after a small amount of travel and does not drop at all. Feels perfectly fine. I have yet to drive the car yet, as I still need to complete the fronts today.

Is there any worry about the reservoir going dry with the MC? Or should it be fine seeing as I basically did a full bleed of the system afterward?

I just want to make sure there will be no issues. I don't expect there to be, but I figure there are more knowledgeable here. Was a silly mistake on my behalf!

 

[Trav]

No problem. Just don't let the pedal go all the way down to the floor when bleeding as it can possibly damage the piston seal.
Just put an approx 3/4- 1" thick block block of wood under the pedal to prevent full travel.

 

[xBa380]

Thanks! I always had my helper give me a heads up when it was close to the bottom, so it was never completely bottomed out from what I know! That way I could close the bleeder screw before end of travel to make sure no air was sucked into the line.

 

[Gokhan]

If the reservoir gets dry, you must bleed the master cylinder. Bleeding the wheels won't help.

Make sure to get a brake-line wrench. Some (especially Japanese) are better than others. Never use a regular wrench because it will strip the line nuts and then you will have to replace the lines.

This is the procedure:

(a) Disconnect the brake tubes from the master cylinder.

(b) Depress the brake pedal and hold it.

(c) Block off the outlet plug with your finger, and release the pedal.

(d) Repeat (b) and (c) three or four times.

(Note that if the master cylinder was removed, it could also be filled with brake fluid and bench-bled before installation. No further bleeding of the master cylinder will be necessary in that case.)

After bleeding the master cylinder, bleed the four wheels again, starting with the longest line and then the second longest etc.

 

[xBa380]

That is why I had asked... I have been reading conflicting stuff on what you should do if it happens. I don't think it went bone dry or anything, but enough that air was in the fluid as I bled.

I read to do the above if the pedal feels squishy or anything like that. But other things have mentioned actuating the pedal quickly to pulse bubbles out of the MC with the reservoir cap open.

I guess I will see how the brakes feel when the job is all done. As of now, it appears the pedal is very firm and working as it should with no ill-effects.

 

[Gokhan]

Bleeding the master cylinder isn't really difficult if you have a good brake-line wrench. You should get one and do it. Don't overtighten the nuts though. I had bench-bled mine when I rebuilt it.

 

[The Critic]

If bench bleeding is needed, the pedal won't feel normal.

If the pedal feels fine, you're good to go.

 

[Gokhan]

These seem to be good brake-line wrenches, metric and SAE:

http://www.autozone.com/autozone/accesso...ier=914124_0_0_

http://www.autozone.com/autozone/accesso...ier=914129_0_0_

You don't need to bench-bleed of course. You can bleed on-vehicle by just disconnecting the tubes.

 

[oldhp]

Put a pointed plastic tip cap on a Qt of brake fluid. Cut open the tip and slide a 5/16" hose on the tip. Right off the tip I installed a cheap 5/16" plastic open/close valve. Use good old duct tape to make a hook/hanger on the bottom of brake fluid Qt. Hang the bottle over the MC. Cut another piece of 5/16" hose so it goes into the top opening of MC. Open valve, you now have a extra Qt to bleed brakes. Old trick my Dad showed me to bleed brakes by yourself without worrying about running MC dry. The brake fluid will not run out the top of the MC.

 

[Trav]

Originally Posted By: The Critic
If bench bleeding is needed, the pedal won't feel normal.

If the pedal feels fine, you're good to go.


Yep. If there was air in the MC you would know it. Don't create more work than necessary.
If it doesn't drop or feel spongy after sitting, its fine.

 

[artificialist]

I sure hope your ABS module hasn't been affected. Sometimes when that happens, you have to use a special scan tool to properly bleed the brakes.

 

[yonyon]

Air really shouldn't have gotten into any of the ABS bits unless someone did something odd while there was air in the lines, but one good ABS stop without a low pedal feel afterwards would be enough to be sure.

 

[Gokhan]

Pedal feel is not that it's either hard or soft. There is a range of feel. If you have a bubble or two, it may feel hard enough, but that doesn't mean it won't get harder if you remove them. It all depends on how much air is in the system and you can't judge for sure if you have completely removed all air just by the pedal feel. That's why I would bleed the system if I am in doubt. It makes a big difference in brake performance even if you remove a single bubble.