[Prev][Next][Index][Thread]

Re: brake fluid bleeding/changing

- -------------------------------------------------------------------
Excellent FAQ on bleeding brakes from the now famous Don Eilenberger/BOHICA
pair -- just hope his wife isn't on the list :-).

Just a couple of things I'd like to add.

> 10. YELL to wife... "press down on the brake, and HOLD IT DOWN"
> 11. Open bleeder - hopefully you'll see lots of gooky brake fluid coming out.
> 12. Wait for wife to say "It went to the floor"..
> 13. Attempt to close bleeder BEFORE wife lets pedal up.
> 14. After bleeder is closed, yell to wife "OK - let the pedal up"
> 15. She will yell "I already did"
> 16. Curse and explain the process to her again. "Hold the pedal down until I
> say let it up.."

Letting the brake go to the floor is not a good idea -- especially if you have an
ageing car. The water in the hygroscopic/hydrophillic brake fluid causes corrosion
to develop on the inside of the master cylinder beyond where it normally rubs against
the master cylinder. So, pushing the pedal to the floor (which is not usually how far
the pedal travels) will cause the piston to break into this corroded area and get
damaged.

So, open the bleed valve only a little (1/2 turn) so the pedal moves down slowly and
close it when the pedal reaches half-way to the floor. This will cause the process to
take much longer == many more roses/stressed marriage/no wife + no mail. But would
you rather risk having to replace your master cylinder????

Also, instead of 10-16, I'd suggest 10a- and 10b which seem to be what Bentley says,
and which worked for me. The difference between ABS and non-ABS is the number of
times you need to pump the brakes before holding them down -- 12 for ABS and 4
(I think) for non-ABS.

10a. Yell to wife... "pump brakes 12 times". Wife... "1,2,10,12" (at which time you
     promise her a caribbean cruise) and bg her to count properly.
11a. Now, ask her to hold the pedal down. Open the bleed valve and tell her to yell
     when the pedal falls half-way. Close the bleed valve when she yells.

Remember 1. the bleed valve should be open only when the pedal is being steadily
pressed down, and 2. the pedal should never travel more than 1/2 way to the floor
- -- even while pumping.

12a. Repeat 10a-11a till fresh fluid starts coming out of the valve -- you'll know
     because the old fluid is usually darker.

1/4" clear tubing from a plumbing supply store works well. It fits really tight over
the bleed valve (good). After you do one, and before you do the next one, snip off
the expanded section of tubing, so it will fit nicely on the next one too.

Also: Top off the fluid reservoir every time you bleed about 100-150cc.

A tiny 8mm (either that or 7mm) closed/open end wrench is required. A socket
wrench will not do.

Clean around the top of the brake fluid reservoir before you open it and also
around the bleed valves - and I mean really clean. Keep the reservoir lid and
brake fluid bottles closed except when you are pouring fluid.

Also, while this process can be done without taking the wheels off, don't torture
yourself. Take them off one at a time as you bleed the corresponding brake.

Bentleys suggests other (perhaps less wife-intensive) means of bleeding the brakes
if they are non-ABS, but suggest you use the above method for ABS.

Hope this helps.

Ahsun
- -------------------------------------------------------------------
Ahsun H. Murad (murad@domain.elided)