Steering wheel shaking during braking

Just to double check before I tear the front end of my car apart - I've had
rotors replaced a year ago along with pads. Car was recently aligned.
Checked at Saturn dealer. mentioned car was in previous accident, thus why
the sunroof was stuck closed (duh?.) Saw no other problems. was too foolish
to ask about brakes - was more focused on the secondary engine oxygen sensor
after the cat, but I'll have that problem taken care of (just need to weld
in a new pipe.)

So anyway, at highway to stop, it goes like this. the harder I brake, the
more the steering wheel shakes and shutters like I'm driving over someone's
stairway. (Shakes back and forth.) Peddle has some shake, but I don't pay
attention to that as my hands are shaking all over. As the car slows down to
about 20mph, you can feel a steady "grip and slip" in the brakes, esp. if I
back off to a light brake. the car jerks as if its braking, then coasts,
then feels like they grip again.

Also, if it is my rotors as I suspect, any tips to get the caliper bolts out
without breaking them again?
(I don't have a cutting torch so don't suggest that?)

I have new pads and rotors in my trunk!

 

Sounds like the rotors again. They probably warped from overheating due to a
dragging brake pad.

If they are only a year old, they might have enough meat to have them
re-cut. Personally, I'd get new rotors. Make sure that the calipers move
smoothly and are not bound and the pistons move easily. Are you fairly
certain that it is the front brakes and not the rears? Some cars have the
handbrake act on the rear service brakes (not so with my L series that has
disc service brakes on the rear along with drum park brake - fairly common
for ABS / traction control systems). If the handbrake acts on the rear disc,
pull it gently while moving to see if it has a similar pulsation. Worst come
to worst, remove the wheels and check for runout as the rotor is turned.
Doesn't take much to create the pulsation especially if it is a thickness
variation rather than a wave warp.

I had a stuck pad on my LW300. When I replaced the rear rotors, found the
pad solidly jammed into the calliper. Took it all apart and cleaned out any
rust in the guide channels so that the new pad would slide smoothly. Then
applied silicone brake grease to all sliding surfaces and re-assemble. Works
**much** better now. This especially since the unbalanced braking force on
the rotor caused stress cracks (radially out from rotor hub)!

Stuck bolts - a good penetrating fluid (I use Kroil from www.kanolabs.com )
and an impact wrench. A good impact wrench is worth the purchse. I had a $40
1/2" drive model that was better than nothing. Got a $180 thundergun and the
difference was night and day on the same compressor and tools. If you don't
have access to an impact wrench, get one of the hammer driven manual impact
tools. Again, it is better than nothing but swinging a 2-5# hammer in tight
quarters can be pretty hard. The idea is to break loose the rust which is
brittle. Also there is often blue thread-lock compound on the calliper
bolts. I have sometimes had to heat the assemblies to about 300F in order to
soften the thread lock - but you said you don't have a torch...

 

If you have rear drum brakes you will want to check the brake cylinders. I
had the same type of problem and found that the brake cylinders were leaking
making the front brakes work harder to stop the vehicle. Front pads were
unevenly worn.

 

Well, I did a ton of reading. And I'm certain its the rotors...Also they
mention that you should adjust them so the pads hit the rotors right (??)
not sure how to do this and what equipment I'd need. I'm curious if I could
toss them on and have Midas bleed and adjust them before I brake the pads in
too much? I also need them to weld on a joint in my exhaust so perhaps
that'll work. Hmm. Something about "runout?"

Perhaps my dad will let me bleed the brakes in the garage, we'll see.
Haven't talked to him yet. Though after conquering the hub bearing on my
own, I think this should be trivial (I may be able to get him to buy a
torch. any suggestions?)

Oh, and my car doesn't have rear disk brakes, it has drums!

 

The brake fluid should be almost clear. When you do a brake job, always
bleed the cylinders. If it is dark, keep bleeding (and adding the correct
fluid to the reservoir) until the purged fluid runs clear.

Runout is wobble in the rotor. The wobble comes from either the wheel
spindle or mis-seating the rotor on the spindle face. The pros will usually
sand off any rust on the spindle face that the rotor seats against to ensure
a flat mating. Runout is measured with a gauge anchored to the caliper
usually. The gauge should be perpendicular to the rotor surface and as the
rotor is turned by hand, the height variation can be read on the gauge. I've
done this so long that I just rest my thumb against the caliper bracket and
lightly drag my thumbnail against the rotor surface while spinning it with
the other hand. Works well down to about .010". If you need better than
that, break out the gauges and magnetic base...

 

Is it necessary to check? In other words- Do I need to go rent a gauge?

As for getting the caliper bolts unstuck - which should I purchase:
Mapp Gas/Oxygen Torch ($50, but may serve more than this use)
Propane Torch
Mapp (only) Torch

 

Unless you are a purist or can't fix a pulsation problem any other way,
don't bother with a gauge. When you put a drum or disc rotor onto the hub,
make sure that there is no rust or dirt build-up that would keep it from
seating flat to the hub.

With the wheels off the ground and enine off, pump the brake pedal a few
times and then try to rotate the wheel by hand to find any binding spots. If
you have removed the wheel and are turning the rotor or hub, make sure that
you use at least 3 lug nuts to keep the rotor flat against the hub.

I've used a turbo torch with mapp /air. works pretty well but the flame is
large. There are times when you would like a spot heating which you get
better with the mapp/ oxygen. Both options are much hotter than propane
alone. You can also use propane/ oxygen but it is not as hot as mapp/oxy.

When using any torch, be aware that you want to heat the area around the
bolt and not the bolt itself (usually at least). Heating too much will
destroy the temper of a bolt and it will have to be replaced (not a bad idea
to replace cirtical bolts anyway*). You also don't want to burn seals or
boil the brake fluid. If you don't have a decent impact wrench, it is a good
tool to have on hand.

* Many bolts are specified for a single tightening. These are 'stretch
bolts' that keep tension. Mostly used on cylinder heads where you torque to
a spec and then continue so many degrees further. Steering knuckle to ball
joint lock bolts used on many cars are specified to be replaced every time
that they are removed. Most everybody re-uses the old bolts and the spec is
more to keep the lawyers happy since it is a critical joint.

 

Just get some PB Catalyst at the autoparts store or walmart, spray it
on, tap the thing pretty hard with a hammer, wait and repeat.
Shouldn't be that stuck. They might be in pretty well, but I'm sure
you can get them loose.