I think it is too late for most cars re: rust in/on the hydraulic lines.
Best bet is to replace all lines using your old ones as templates. I put
all new brakes all the way around only to have to replace them several
years later because of rust and such. I used silicone and bled them
every 2 years.
It was the RUST in the lines that killed them not BEAUTY!!!!!
Consequently I bent all new lines and no problems since.
-----Original Message-----
From: John F Sandhoff [mailto:sandhoff@compctr.ccs.csus.edu]
Sent: Wednesday, March 08, 2000 10:00 AM
To: datsun-roadsters@autox.team.net
Subject: Brake bleeding lesson (LOOONG)
Okay, since brakes are once again the topic, let me toss out a couple
comments for those relatively new to the list (you old timers can skip
this message, you've heard me say it before):
Brakes: The parts are expensive and they corrode from disuse.
So at LEAST every two years, and preferably every year, FLUSH
the system. Suck out the old fluid from the master and refill it, then
pump enough fluid thru the system (one wheel at a time, starting with
the wheel furthest from the master - as measured by how the tubing
runs). Keep the master topped up and get all the old fluid out of there.
Many of us use Castrol GT/LMA, it's DOT4, high boiling point, not
expensive. Silicone (DOT 5) presents a whole new set of problems.
Works best if the system is really tight and you pressure bleed
(http://www.motiveproducts.com; they claim they'll have an adapter
for our 'pop-on' caps soon).
Once the caliper bodies pit, you'll have a problem. You can buy
new ones, about $65 per unit (4 needed), have yours resleeved
(expensive but they shouldn't corrode again), or buy new stainless
steel units (http://www.hyedracyl.com). May want to use some
speed bleeders, too (http://www.speedbleeder.com).
As far as rebuilding the master cylinders: The bodies are aluminum
and easily corrode. Chances are very good (very bad?) that the
bores cannot be cleaned up without removing excessive metal.
The steel outlets 'weld' themselves to the aluminum after 30 years
are often can't be removed. All in all, chances of rebuilding a gunked
up master is poor. New masters are around $150 (youch!).
And the reason I started writing this in the first place: bleeding your
brakes, or replacing the pads, may cause problems :-(. This does
not mean you shouldn't service your brakes! It just means be aware
of what may go wrong a week after that brake job! Imagine that master
cylinder full of gunk. There's no gunk in the small area the piston
sweeps
during normal use, but a caked-on pile lies just beyond. Now you bleed
the system: open a valve, press the brake pedal to the floor. Oops! You
just dragged the rubber seal over that pile of gunk! Do that a few times
and you end up with a nicked seal that starts to leak! Pretty soon
you're
pumping brake fluid onto your carpet!
Same thing with the front calipers: When you replace the pads, you push
the pistons back into an area that's probably full of gunk and pits. The
fluid leaks around the seal thru the pits and viola: your new pads are
soaked. Grrr.
How do you minimize this agony? Bleed those brakes often! Don't let
the fluid get contaminated, and you won't rot out the insides of your
brake system!
-- John
John F Sandhoff sandhoff@csus.edu Sacramento, CA
|