Bleeding brakes

[btfarm]

proper procedure is to bleed the shortest line first.LF,RF,LR, RR.And repeat if needed.

I've always done the longest to shortest. Done it that way for 45+ years.

A bleed kit works good too. A slightly higher tech solution to the hose in a jar trick. You still have to finish up with the 2 person power bleed to make sure though.

 

[Anubis]

I use a hand vac pump ....... haven't had any problems with soft pedal.

How long has the Master cylinder been in there?

 

[bison]

well,i guess there seem many ways to skin a cat. as long as one get the brakes bled and work, do what ever blows your hair back to get it done.

 

[ak diesel driver]

Master cyl is orig. Today while driving back and forth to church I had excellent brakes just feels diff.

 

[Detroit Dan]

Nothing wrong with getting all that old fluid outta there either

 

[Tookie]

GM says you bleed them as if the ABS isn't there, and you ONLY need to activate the ABS to bleed them IF you replaced one of the ABS solenoids.

If air gets into the ABS unit, you will have activate it to get the air out.
In my case, I changed both wheel cylinders, and both calipers, took everything
off at once so I didn't have to make a return trip to the parts house for the
core, and the lines drained out. Had I swaped them one at a time, I probably could
have avoided getting air into the ABS

 

[nobby]

As already stated caliper change should not require ABS bleeding as you are not introducing air higher up in the system as long as you do not run the MC dry whilst bleeding that is (especially if you used brake hose clamps). Also rears should not need bleeding either as they are a separate system although it does no harm and helps flush out old fluid to bleed the rears also. Although I also believe that running the MC dry will not put air into the ABS as it will be in the unactivated state a closed system and hence air should not get in. IIRC the manual says that only work specifically on the ABS components requires an ABS bleed.

Calipers have a habit of air bubbles sticking to the piston face and the bigger the bore of caliper the more the issue this is. Tapping the caliper with a hammer inbetween bleeds aids this as it helps shake of the tiny bubbles.

I have sometimes found with calipers coming back a few days later helps get the remaining air out of calipers.

If you still wish to bleed the ABS and no scan tool with the command ABS feature all you need to do is find a gravel track and brake hard to activate the ABS and then bleed again, all the scan tool does is command the ABS to cycle on whilst stationary.

I have recently put a large effort into achieving a firmer pedal with many new components and have bled and flushed enough that I am confident that there is no more air and that's just the way it is. Internet searches have found much concensus that GM brakes can be shy in the firmness department. Also conceptually beware the fact that the brakes were possibly somewhat soft before and that in doing brakes you are hyper aware for a firm pedal that may never really existed prior. It pays to before doing brakes if possible try to fix in your head just how firm your brakes were before the job. Of course this is relative as you may be replacing faulty components that are in fact giving a poorer pedal. At least you fix a reference point to see if it gets better/worse or stays the same after the job. This is an interesting read re GM brakes from a trade perspective:

read gb1098
http://www.mightyautoparts.com/pdf/articles/gb1098.pdf

read tt125
http://www.mightyautoparts.com/pdf/articles/tt125.pdf

Also do not forget to check rear drum adjustment, out of adjustment rears will take away apparent firmness as travel is slightly increased.

cheers
Nobby

 

[guybb3]

Speed Bleeders are worth their weight in gold. I would never be without them on the Sub.

 

[Tookie]

I also believe that running the MC dry will not put air into the ABS as it will be in the unactivated state a closed system and hence air should not get in.
Nobby

Everybody is entitled to their opinion, wrong or right. :smile5:
Where exactly do you think the air is going if the MC goes dry?
You are correct about changing a caliper not putting air in it, IF you swap
hoses quickly, or use line clamps (I never liked the idea of crushing
the reinforced rubber hose down enough to cut off flow, stresses it
more than I feel comfortable doing on a line that may see 2000 PSI)
Regardless of HOW the air gets in, if it does, the dealer(s) I talked to
said it had to be activated to get the air out of the passages.
As you said, if you find a large gravel or dirt road, you could activate it
by slamming on the brakes.