Marc,
Does this happen on every stop, or just when you have been driving and not
using the brakes for a few minutes? A warped rotor can cause one of
the pads to be pushed back a bit farther than the other pads, causing
that pad to apply slightly later than the others. With the rain that we
have had lately it is possible that one front brake has been getting
wetter than the other, lubricating the brake pad/rotor, allowing less
braking action than the other one.
First check the thickness of the front pads, all 4 should be about the
same thickness. If one pad is much thinner or thicker than the others it
may indicate a problem with that piston or rotor. (If one pad is thick,
the piston may be sticking and not applying pressure to the rotor. If one
pad is thinner than the rest it could mean the piston is sticking and not
retracting as it should, or it may be that the rotor is warped and causing
more contact between the lining and the rotor, causing it to wear more.)
Next, remove the calipers and pull back the edge of each of the piston
dust covers and see if there is any brake fluid behind them. If there is
fluid, you should rebuild or replace the calipers. They aren't difficult
to rebuild if they aren't pitted. If any of them are pitted, they will
need to be replaced or resleeved.
While you are at it check the condition of the brake hoses, most of our
cars still have the original hoses on them and should have been replaced
years ago! I prefer the braided stainless steel lines from Pegasus Racing.
They require adapters, but Pegasus sells them also. Don't forget the hose
that runs from the body to the rear axle.
Your wheel bearings could be loose or defective causing the rotor to
wobble. Check them and, if you have a dial indicator, check toe run out of
the rotors. Also, check the thickness of the rotors, you may ned to
replace them if they are too thin.
Your rear wheel cylinders probably won't cause pulling as much as the
front brakes, but it is possible. Check the condition of the brake shoes.
The front shoe will have less wear than the rear one, so you can't compare
the wear of the lining to determine if one half of the rear cylinder, but
you can compare shoes side to side.
Check to see if there is any brake fluid leaking past the pistom cups by
checking inside the dust boots. Also check to see if there is any leaking
of the axle seals, allowing differential fluid to leak onto the brake
shoes. (Since you already have the brakes this far apart, it wouldn't hurt
to pull the axle and repack the rear wheel bearings and replace the inner
seal that allows differential fluid to wash the grease out of the
bearings).
Check the steel break lines to see if any of them are covered with a
plastic sheath. If you find any, cut the sheath off. The sheath allows
water to collect and rusts out the brake lines. Check for pitting and
replace any damaged lines.
Check under the dash, inside the boot on the brake master cylinder to see
if there is any fluid. If there is any, the master cylinder needs to be
rebuilt or replaced. If there is any pitting or scoring or pitting in the
bores it needs to be replaced because it can't be honed to take the damage
out. Don't hone the bores if there are no pits or scratches because
honing it will cut through the anodising in the bores, just clean it out
with solvent and replace the rubber parts. Bleed the master cylinder
before you connect the brake lines to it so you won't be pushing as much
air into the brake lines, it makes it much easier to bleed the system!
Blow out the brake lines with low pressure air to get rid of all the old
fluid.
I prefer to rebuild everything when any work is needed, other than just
replacing the pads. Since the braking system is the biggest potential
safety problem on the car (in my opinion), it deserves considerable
attention.
Yearly replacement of the brake fluid keeps the system in better shape.
Brake fluid absorbs water which can cause rust and pits in the cylinders
that causes expensive repairs to replace if not taken care of.
If you find that the brake (and clutch fluid, for that matter) is dark, it
means that some rubber is being worn or oxidized off and is contaminating
the fluid. It is usually the brake hoses, but can be the cups.
I know this sounds like a lot of things to check, but, hey, your life is
worth it!
Peace,
Pat
- Support
Habitat for Humanity, A "hand up", not a "hand out" -
Pat Horne, Network Manager, Shop Supervisor, Future planner
CS Dept, University of Texas, Austin, Tx. 78712 USA
voice (512)471-9730, fax (512)471-8885, horne@cs.utexas.edu
On Sun, 2 Dec 2001, snyler wrote:
> List,
> Looks like I need to start working on the brakes, I noticed a pull
> to the left, not radical but noticeable. Any thoughts or advice on the
> job ahead of me? What to look for? (70 1600 BTW)
>
> -Marc T.
>
> ==========================================================================
> Marc Tyler TDROC Sisterdale TX
> 1970 1600 #SPL311-31016
> 1965 L-320 #L320 013642
> http://datsun_marc.tripod.com/cgi-bin/datsun_homepage.html
>
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