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Kia: 4WD Front Hub and Brake System Service

May 1, 2008

Being import specialist techs, we may not be real familiar with 4WD systems and the associated parts, but that’s no reason to turn away this profitable work. For this article, we’ll look at the 2000 Sportage. The most common complaint you’ll encounter is no 4WD operation, which can usually be traced to problems with the vacuum-actuated front hubs. Kia requires that the driver shift the transfer case into four-wheel-drive, choosing either high- or low-range gearing. The driver must then flip a switch that opens a vacuum-control valve, sending vacuum to the locking front hubs and engaging them to the drive axles. If there’s a weak link in the system, it’s the hubs.

The hubs can cause a couple of problems: The first, and most common, is no engagement. Many times these troubles can be traced to the vacuum supply, rather than a mechanical problem with the hubs themselves. The first step is to be sure you have vacuum at the hubs with FWD engaged and the engine running. If not, work backward looking for the vacuum leak; a convenient test point is the “T” fitting by the master cylinder where the lines branch off to the left and right sides. This “T” is downstream of the control solenoid and vacuum storage tank, so if you have vacuum here, you should have it at the hubs.

Many times, the problem is as simple as broken or disconnected vacuum hoses leading to the hub. But there have been reports of problems with the steel lines running to the wheels. Over the years, these lines can rust, restricting flow and, in the worst cases, causing leaks. There are updated parts available, and Kia has issued a TSB on the subject (see page 41), but line replacement can be a tedious task. Many techs report good success with alternate methods of repair; you’ll have to make the choice as to what’s the best course of action for your situation.

Another problem you can run into with the hubs involves engagement when it’s not called for. Usually described as a noise, in this case the hubs are sticking, and the wheels are engaging and disengaging the drive, the axles and front differential while the transfer case is in the two-wheel-drive position. Many times, simply backing up the truck will take care of this problem, but often it’s an indication that the hubs should come apart, and be cleaned and lubed. Depending on the condition of the original units, replacement hubs may be in order. In the case of the Sportage, this problem can be caused by road grime finding its way into the hub through the previously discussed vacuum system. If the 4WD isn’t used very often, the broken or disconnected vacuum lines could have been overlooked for quite a while.

REPLACEMENT HUBS
Should you find yourself in the position where replacement hubs are required, or if the customer values reliability over convenience, consider changing over to the almost-bulletproof aftermarket manually operated hubs. These units provide a low-cost alternative to the automatic units and, while they require the driver to lock the hubs when 4WD is anticipated or required, many customers find it an attractive alternative.

If you do go with the manual hubs, be sure to seal any of the vacuum fittings on the hubs to prevent debris from getting into the hubs, and disconnect the supply solenoid to prevent a manifold leak when 4WD is selected. Removing and replacing the hubs is a simple job that shouldn’t be too challenging for any level tech, but while you’re going in there, it’s a good time to service the wheel bearings or, at the very least, make any bearing adjustment that’s required.

The rest of the 4WD system on these vehicles presents more service opportunities than diagnostic challenges. Be sure to figure on changing the fluid in both differentials as well as the transfer case when doing a major service on a Sportage. Of course, any work on the hubs will have you checking the brakes as well.

BRAKE SERVICE
Like any repair procedure, the brake service process starts with the customer interview. Some can be as short as the report of a grinding noise when stopping, to a discussion that starts with “I’m not sure what’s wrong, but the brakes just don’t feel right.”

If you’re dealing with the latter, you have to spend the time necessary to find out what it is that’s making the customer uncomfortable. When you think about it, there are only a couple of things that could be happening: It’s either noisy; has a good, firm pedal and doesn’t stop well; the pedal travel is excessive; or it shakes. It gets trickier if the problem is intermittent, but when the interview is over we should have a good idea of where the problem exists. If necessary, send the tech out for a road test with the customer to try to duplicate the problem.

Although not very common with the Kia, master cylinder problems can be one of the tougher intermittent problems to duplicate, and one of the more difficult for the customer to relate. Oftentimes, the problem comes on gradually, but that fading pedal quickly gets the driver’s attention. Whenever faced with a complaint of “my brakes failed but got better,” suspect the master cylinder bypassing fluid.

More common is the pedal that’s good and firm but just doesn’t stop well. Here we’re looking for something that isn’t moving, when it should. Many times, you’ll find rust buildup has caused the pads to get stuck in the brackets, and even the hydraulic pressure in the brake system is no match for it. Don’t overlook the rear-wheel cylinders; frozen pistons are not uncommon in vehicles with high mileage or that don’t get steady usage.

NOISE COMPLAINTS
Many of the complaints we get are noise related. Not necessarily the familiar high-pitched brake squeak, but a grinding noise that’s most prevalent when the vehicle is first driven after sitting. On the Sportage this can often be traced to the rear drums being loaded with brake dust; simply cleaning and servicing the rear brakes will take care of the complaint, while giving the tech the opportunity to inspect the condition of the shoes, wheel cylinders and hardware.

When chasing noises, keep an eye out for rust buildup that can cause interference where you wouldn’t normally expect it, like the drum and backing plate making contact. This noise can come and go as the rust gets knocked off the drum, but will always leave a witness mark. The rust can be cleaned, but it may be more cost effective to replace the drums.

On the other hand, a lot of brake work is generated by the tech finding the pads or shoes are in need of service as other work is performed. When you make the call to sell a job, you’ll often get a “by the way” comment from the customer with a brake concern; be sure the tech doing the job is aware of any issues. Now the challenge is to replace the brakes so they’ll give the customer good service for the life of the friction material.

ABS SERVICE
By now, I’m sure we’re all aware of the risk involved with simply pushing contaminated brake fluid backward through the ABS. The risk of creating blockages in the ABS modulator is just too great to overlook. There’s really no reason not to open the bleeders and slowly retract the pistons, catching the bad fluid in your bleed bottle. You’re going to bleed and flush the system as part of the service, so you might as well get rid of the most abused fluid right off the bat. If the bleeders are seized, now is the time to deal with them, not when the new pads are installed. Again, don’t overlook the rears. I know you already inspected the shoes before you sold the job.

PAD REPLACEMENT
No matter where you live, there’s no debating that brakes live in a hostile environment. This will result in rust and corrosion that has to be taken care of to ensure a quality and quiet repair.

As the pads are being removed, it’s important to look for anything that isn’t moving freely; we’re looking for pads that are worn evenly. Anything else indicates that the workload isn’t being distributed evenly, and there’s a good chance that the pads are hanging up. It’s not unusual for the customer not to notice these problems since they tend to come on gradually. But all of them can feel the difference once the system is restored to its original condition.

BRAKE INSPECTION
As the pads are replaced, the system inspection should continue. Open the bleeder and push back the pistons on the calipers. On the front, we use a C-clamp between the outer pad and back of the caliper. It should take little effort to retract the piston and move the caliper away from the outer pad. If excessive effort is required, don’t force it; instead look for an indication of what’s binding and remove the caliper to further investigate. If the slides are frozen, it will be evident if the piston retracts easily with the caliper removed.

Make note if the pads are sticking in the carrier; either way, lubricate and service the sliders as well as the carrier. Be sure to remove the anti-rattle hardware in the bracket to clean the rust behind them. It’s that rust that will bind the pads, and any binding will result in noisy operation as well as poor brake performance.

When installing the new pads, be sure to lubricate any area where the pad contacts the bracket and insulate the pad backing from the piston and caliper. Squeaks are the result of the pads vibrating against the piston and bracket when the brakes are partially applied. If possible, always reinstall the insulator shims with a little brake lube between the shim and the pad. If the shims aren’t available, or aren’t useable, there are a couple of options. We’ve had better luck with the chemical compounds over the universal shims that are available. Use what works best for you — but using nothing is a sure recipe for noise.

We’re also using an aerosol product that’s applied on the friction material of new pads. We’ve been using it for years with good success and have enjoyed very few noise-related comebacks since.

It’s always a good noise preventive practice to replace the rotors when pads are replaced. Of course, we live in the real world and that’s not always possible. If you’re installing new pads against the old rotors, be sure the pads aren’t going to contact an area of the rotor that the old pads didn’t. In some cases, the unused area of the rotor can be cleaned up. In others, it’s best to let the customer know and note on the invoice that, without replacing the rotors, noisy operation is a possibility.

The same good habits apply if the rear shoes need replacement. Be sure to lubricate any part of the backing plate that the shoe contacts, and don’t overlook the adjuster and handbrake hardware. Be sure the cables are free and lubricated, and the wheel cylinder pistons move as expected. As I mentioned earlier, be aware of the rust and the potential noises it can cause.

No undercar work is complete without an inspection of the steering and suspension. These checks take only a couple of minutes but can pay big dividends for both the shop and the customer. It’s a good practice to get in the habit of shaking and spinning the wheels as soon as the car’s in the air.

Shake the sway bars and check the bushings that mount the bar to the chassis; any looseness will result in a solid noise, and we all know how serious a failure of a steering component can be.

Always remember that recommending required work isn’t upselling the job; it’s providing quality service that will result in a safer vehicle for the customer, and a stronger bottom line for the shop. Nothing wrong with that.

 

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