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Tech Feature: Nissan Undercar Noise and Vibration Repairs

When it comes to Nissan undercar work, Import Specialist Bob Dowie discusses the first challenge you face and that is selling the work. While he uses the word “selling,” what you are actually doing is making the customer aware of issues that need to be addressed to maintain the reliability and, more importantly, the safety of their vehicle.

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This month, we’re going to be looking at the Nissan line of cars and trucks with an eye toward common problems we’ll see with the brake and suspension system. For the experienced tech, neither of these systems should present a problem, but there are some common issues that can save you some time if you keep them in mind.

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When it comes to undercar work, we’re going to talk about the first challenge we face and that is selling the work. While I use the word “selling,” what we are actually doing is making the customer aware of issues that need to be addressed to maintain the reliability and, more importantly, the safety of the vehicle.  

We’ve always been aware of the benefits of preventive maintenance, and many of us depend heavily on that work to remain profitable. This makes it even more important that we let every customer know we are more than able to handle all of their vehicle service needs, but it’s critically important that you don’t oversell. The customer expects and appreciates that you’re looking at the car with their best interests in mind, but it won’t take long for the word to get out if you’re overselling.

CHASSIS CHECKS
The most frequent suspension and steering system-related problems are noise-related, with knocking and squeaking at the top of the list. Other complaints include poor handling, tire wear, drifting or pulling, and vibration issues.

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We’ll look at a 2001 Sentra with 120,000 miles that was brought in with a customer complaining of squeaking and knocking noises. We were lucky with this one: A push and lift on the left front wheel well revealed the distinctive up and down “bed spring” squeak. And a quick drive on a road in poor conditions revealed the knock. Our experience told us that this type of squeak is often the result of a ball joint or tie rod end that has a damaged boot, which allows the lubricant to escape, and dirt and moisture to get in. The resulting rust tightens up the joint and produces the noise.

The knocking noise sounded like the familiar problem of loose sway bar links or bushings that mount the sway bar to the chassis. This problem is often misdiagnosed; it takes only the slightest amount of play in these components to result in big noises.

If you don’t have a drive-on lift, you’ll be forced to the creeper to confirm the diagnosis. Using a mechanic’s stethoscope, have an assistant push on the fender as you confirm the source of the noise. If you suspect the tie rod end, a twist of the rod should result in the same noise. This is where our good luck vanished; although we could duplicate the noise, we couldn’t really pinpoint the source.

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The knocking noise also presented challenges. After hearing it on the road test, I was surprised we couldn’t duplicate this noise using the same push-and-lift technique that revealed the squeak. We looked closely for any free movement in the suspension, paying particular attention to the sway bar mounts and the links. We didn’t see any, so our search for the knock continued back on the frame contact lift. Using pry bars, we again tried to move the sway bar and its links, as well as the lower control arm bushings, but still couldn’t find any movement.

We looked at the bolts that mount the subframe to the unibody, keeping an eye out for rust around the bolts since it’s a dead giveaway that movement is taking place. But we didn’t find anything there either.

At this point, we replaced the suspected lower ball joint, planning to confirm the problem as the job progressed. With the joint separated from the knuckle, it moved freely and quietly. But any movement of the control arm confirmed the noise was coming from the bushing. Side movement on the now-unloaded arm revealed a small amount of play at the outside of the same bushing, which caused the knocking noise. As the arm was removed, the problem was obvious. The bushing had separated and was moving in the bracket. While this is not a common Nissan problem, you can be sure we’ll look more closely at the bushings in the future.

TIRE AND VIBRATION PROBLEMS
Tire problems will often produce handling problems. If you’re faced with a drifting or pulling complaint, look to the tires first for the cause. It doesn’t take much stagger (difference in circumference) to cause a pull. We use a narrow 10-foot tape that conforms nicely around the tire. In minutes, all four properly inflated tires can be measured, letting you make an educated decision on where to mount them on the car.

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The same goes for vibration complaints. The most important thing we need to establish is when the ­vibration occurs, and whether it’s a noise or something that the customer is feeling. We’ve had many customers complain of a vibration when they’re actually talking about an exhaust shield rattle or the growling noise caused by a bad wheel bearing or cupped tire. Like any other repair, if there is any doubt about the complaint, a road-test with the customer is the best way to ensure the right problem is addressed.

We’re all experienced with tracking down steering vibrations and should have no trouble with Nissans. Tire condition has to be considered, especially if rotation service has been ignored; it’s not unusual for cupping to take place on the rear tires. Such uneven wear will often mimic a bad bearing, and will certainly cause a noticeable vibration through the seat. This cupping is often thought to be the result of weak rear struts, but I would hesitate to recommend strut replacement if cupping is the only symptom experienced.

A better solution is regular tire rotation. If the struts are showing signs of leakage, or fail the time-honored push test, they should be replaced, but still recommend regular rotation service to your customer.

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While we’re talking about vibrations, we have to consider the front-drive axles, CV joints and brakes. If the shake changes under load, it’s a safe bet there is a worn inner CV joint. The challenge is determining which side is the offender; or it could be both. Since we see this only on high-mileage vehicles, we recommend replacing both axles with quality, rebuilt units.

If the customer reports an intermittent vibration that can’t be pinned down, look for evidence of a sticking brake caliper and the overheating it causes. You would think the driver would smell the overheating brakes, but that isn’t always the case. The ­vibration, however, will get the attention of anyone. We also have to consider the vibration caused by warped rotors. If we’re at the service counter, a road-test with the customer is in order.

Although the Nissan suspension system is very ­reliable, there are a few problems worth noting on the popular Pathfinder SUV. If you’re faced with a complaint that the back of the vehicle is “rocking” from side to side, it’s a pretty accurate description. This condition often shows up at interstate speeds and ­really gets the driver’s attention. Also common on the Pathfinder is a squeaking noise from the front wheels, not unlike a brake pad sensor. These problems can be diagnostic challenges if you’re not armed with the proper information.

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The rocking problem is cured with the installation of upgraded rear trailing arm bushings. The challenge is that the bushings don’t look worn and no noise is evident. We’ve seen shocks, springs, tires and driveshafts replaced without success.

For the wheel noise, an updated baffle or dust shield is available to prevent the contact that’s causing the squeak. Since this noise sounds a lot like a brake squeak, and most of us wouldn’t think of contact between the shield and the seal, a lot of time can be spent looking elsewhere.

The popular Murano crossover is equipped with a fluid-filled rear control arm bushing that does a good job of isolating harshness, but can be challenging to diagnose for movement that will result in noise. One of the more simple methods of confirmation is to drive the vehicle at low speed and hit the brake abruptly; the noise will be evident as will the movement of the wheel to an observant assistant. The best course of action on the Murano is to replace the arm and bushing as an assembly. This method is equally effective with any bushing that controls movement that will be induced with braking. If the bushing is allowing excessive movement with this test, it’s a safe bet it’s making noise over surface irregularities.  

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There have also been some reports of a front knocking noise on the mid-2000 Maxima and Altima that sounds just like play in the sway bar bushing or links. While it’s unusual for a strut to make noise with no additional symptoms, there have been reports of these struts making noise as a result of excessive clearance in the shaft bushing. You would think these struts would be leaking, but that is not always the case.

BRAKES
Brake problems will present themselves in a couple of ways. The most common complaints are noise-related. Nissan, like many other manufacturers, makes use of the simple and effective tab-type sensor that will contact the rotor when the pads need to be ­replaced. The resulting, high-pitched squeaking noise has proven to be very effective in getting the driver’s attention. That’s not to say that people won’t ignore it; rather they drive until the brakes are making that distinctive grinding noise that indicates the friction material is gone and metal-to-metal contact is taking place. Of course, in that case, the car should be parked until repairs are made.

Many of the occasional, annoying noises that disc brakes make are a small trade-off for the braking performance delivered by the system. Oftentimes, just explaining that to a customer goes a long way toward settling their concerns that something is wrong with their brakes.

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But, any noise that is more than occasional should be investigated. Some noise will be the result of rust on the rotors, calipers, hardware or even the brake pads themselves. Use only the best parts, replace questionable units and make sure that the brake hardware is in good condition or new. Also make sure that all the metal-to-metal contact areas are being lubed with the proper grease that’s designed to do this tough job in a harsh environment.

The rotors come into play again if you’re faced with a brake-related vibration. The most common is a ­vibration while braking that’s caused by uneven rotors. Ask your customer a couple of questions that could help ensure a quality job. When did you notice the problem, and what happened to cause the problem? Did you have any tire work done lately? If so, it’s likely you’ll find that the lug nuts are unevenly tightened. To confirm this condition, loosen the lug nuts by hand. More often than not, the overtightened nuts will be obvious.

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The biggest enemy of the rotor is heat. The rotor has a tough job on a system that’s in good shape, but it doesn’t have a chance on a system that has excessive heat-causing drag. Take a good look at the rotors as they’re removed for signs of overheating. It makes little sense to install fresh parts only to subject them to the same conditions. It could be that the last tech who did the brakes missed one of the steps we just talked about or, more likely, the increased mileage has caused a problem. Either way, if it’s not corrected, your new rotors will soon be in the same shape as the ones you just took off.
With high-mileage vehicles, you could be faced with a “brake pedal sometimes fades to the floor” complaint. Although it’s not a common complaint on Nissans, a little detective work is required in such cases. If the pedal fades as the vehicle comes to a stop, often in a situation where the pedal is being partially applied in anticipation of coming to a full stop, it’s a safe bet the master cylinder is the culprit.

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If, on the other hand, the condition results from a long ride at highway speeds, it’s likely that excessive drag is causing the fluid in the calipers to overheat, resulting in brake fade. When the brakes cool, the pedal often will return to what feels like “normal” to the customer. Many times, the customer will report a burning smell and the worse cases will cause a severe vibration. It takes a stuck caliper to generate the degree of heat needed to cause these problems, and they certainly should be checked closely.

You should be able to find the problem wheels by inspecting the rotors. If that much heat was generated, the rotors will show the signs. If you can duplicate the tight wheel, don’t be too quick to condemn the caliper without cracking open the bleeder to be sure there’s no pressure in the line. If pressure exists, backtrack through the hydraulic system until the ­restriction is found.

Nissan uses a hand-brake that is incorporated into the rear caliper. We know everyone doesn’t use his or her hand-brake on a regular basis, and we also know that a mechanical device doesn’t like to sit around not being used only to suddenly be forced into service. The same thing can be said for the cables. If the hand-brake levers aren’t returning on the caliper, be sure that the cables aren’t binding. The complexity of the hand-brake does make the rear calipers a little pricier, but I still like to replace them in pairs to maintain the balance of the brake system.

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ABS AND VSC SYSTEMS
While the ABS system on the Nissans has proven to be quite reliable, there have been reports of some problems but, more importantly, it has changed the way we perform brake service. While it has always been important to practice good work habits, with the brake system now being integrated into both the anti-lock brake system and the vehicle stability control system, it’s more important than ever that the mechanical application and release takes place as expected.

Equally important is the quality of the fluid and our responsibility to maintain it. The first step is to never push the dirty fluid backward through the system taking the risk that you’ll plug up a port in the ABS controller that will lead to ­replacement of this expensive unit. Always open the bleeder at the caliper before pushing the piston back, attach your bleed line catching the dirty fluid and never miss an opportunity to flush the brake system. And, at the very least, a thorough flush and bleed should be performed whenever the pads are replaced.

When it comes to problems you may see with the ABS system, most will be related to wheel speed ­sensors not reporting the wheel speeds correctly. The challenge is finding out why the signal is wrong. The first step is to pull the codes, the second step will have you checking the service information and ­forums for TSBs and other information that will help in the diagnostic process. As an example, there is a TSB for the 2005 Maxima related to the rear speed sensors and hub and assembly mounting surface.

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Other things to keep in mind is that like engine codes, brake and ABS codes are circuit-specific and not sensor-specific. Always confirm the code by checking the signal at the sensor. If you’re getting the expected signal at the sensor and the code persists, confirm the signal at the control unit as there have been some reports of harness problems.

Other than the ABS or traction control warning lamp being lit, the most common problem you’ll see will be unwarranted ABS engagement. This will often be the result of a wheel speed signal dropping out at low speeds. When diagnosing this problem, the first step is to identify the wheel that’s dropping out, then determine why; in this case, it may be the sensor but it could just as easily be a cracked tone ring, or corroded connections in the harness. It doesn’t take long to check for either and, as always, a solid diagnosis will lead to a solid and profitable repair.

To turn these kinds of jobs into profit-makers, get in the habit of checking your service information. Check for TSBs, or even more valuable websites such as ImportCar, iatn.net and some of the community sites hosted by parts suppliers. All of them will let you search for problems and, with ­almost 50,000 techs on iATN alone, it’s a safe bet that someone has already seen it.

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