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!

Reply to
HyperCube33 (Life2Death)
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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

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) 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...

Reply to
Oppie

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.

Reply to
Jim Newsgroups

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!

Reply to
HyperCube33 (Life2Death)

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...

Reply to
Oppie

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

Reply to
HyperCube33 (Life2Death)

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.
Reply to
Oppie

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.

Reply to
sowhatofit

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