2000 Pontiac Grand Prix noise when braking and turning.

Tiny
COOLEYSNOW
  • MEMBER
  • 2000 PONTIAC GRAND PRIX
  • 3.8L
  • AUTOMATIC
  • 225,000 MILES
For the past few months I have been hearing popping noises coming from the front of my car whenever I brake or turn after driving for a while. Could it be a damaged motor mount or what else could it be. I know its not my bearings or my tie rod ends because they have been replaced within the last year
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Monday, February 3rd, 2014 AT 9:44 PM

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Tiny
CARADIODOC
  • EXPERT
Actually, GM has a lot of trouble with their front wheel bearings. They commonly cause trouble in as little as 15,000 miles, but not noises. The two most common causes of a popping noise are worn lower control arm bushings and binding upper strut mounts. Do you want to diagnose this yourself? If so, I'll describe how to inspect the suspension parts. Otherwise have the car inspected at a tire and alignment shop. They're good at finding the causes of noises, tire wear, and handling problems.
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Monday, February 3rd, 2014 AT 10:02 PM
Tiny
COOLEYSNOW
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Yes I would like to know how to diagnose it. Also, how much would it cost to get this fixed
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Tuesday, February 4th, 2014 AT 8:05 AM
Tiny
CARADIODOC
  • EXPERT
We don't get involved with costs here because there's way too many variables. We don't even know what's wrong yet.

The upper strut mounts are the easiest to diagnose. Reach over the top of a front tire and wrap your fingertips lightly around the coil spring. Have a helper slowly turn the steering wheel left and right. You should feel the spring rotate smoothly with the wheel. If the mount is binding, you'll feel the spring wind up and build tension, then suddenly pop free and turn. That usually doesn't happen when the car is moving because bumps in the road will let it unload and turn easier.

Control arm bushings help to hold the wheel in proper position. Any road forces that put pressure on the tire will cause a worn bushing to shift position, and if the rubber isolator is deteriorated enough, you'll hear a dull metal-on-metal thud. You need to see if you can make one of the bushings move by hand, so the car will need to be jacked up and supported with jack stands under the frame rail or cross member, not under the control arm. There can't be any pressure on the control arms because that would hold them solidly in place. Once the car is safely supported, use a pry bar between the arm and the frame where the arm attaches and try to pry the pivot point back and forth. Usually if the bushing is worn enough to make noise, it's worn enough to move easily by hand. Also look for chewed-up rubber, or a rust-colored powder around the pivot bolt.

A worn strut will cause a rapid, repeated dull rattle, mainly when driving straight ahead, and it will be easiest to hear at lower speeds. With the car resting on the tires, reach through the coil spring to raise the plastic or rubber boot, the rest your fingertip on top of the strut body with the tip of your finger touching the shaft. Push and pull on the top of the tire to move the strut back and forth. You're trying to feel if the shaft is moving sideways at all. That can be real hard at first to determine because if the car body moves up and down even a little, the shaft will move up and down in the strut body, and that can make it feel like it's moving sideways. There must be no sideways play between the strut body and shaft. When the strut is badly worn, that sideways play will be real obvious.

Worn tie rod ends don't usually cause a noise. Ball joints are checked in different ways depending on the style. Older Chrysler products used a wear-indicator grease fitting. If it was loose, the ball joint was ready to be replaced. On older GMs, the grease fitting was screwed into a round piece that stuck down below the bottom plate of the joint. If that round piece was recessed, the joint was worn. If you could catch your fingernail on that piece, the joint was okay. On the newer cars you have to go by visible movement between the ball and socket. The joint has to be "unloaded", meaning it has no pressure or tension on it. For strut suspension systems, that almost always means supporting the car the same way as when checking the control arm bushings. Try prying the control arm up and down next to where the spindle attaches. There should be no vertical movement between the two parts of the ball joint. Next, watch for sideways movement between the ball and socket while a helper tugs the tire left and right. The steering wheel should be locked to prevent the steering linkage from turning. The tire is just a big lever. It will push and pull the ball joint stud inside the socket to show if there's any sideways movement, which is unacceptable. It should be noted that while up and down movement between the ball and socket indicates wear, it is normal to find about 1/8" of movement in some brand new ball joints, and that is normal and acceptable. That mainly applies to Dodge Dakotas. That movement does not affect tire wear and does not cause a noise. You WILL find that vertical play when checking those lower ball joints.
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Tuesday, February 4th, 2014 AT 4:02 PM

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