Pelican Technical Article: Wheel Bearing Replacement Wayne R. Dempsey
Time: 4 hrs
Tab: $120
Talent:
Tools:
Wheel bearing puller, breaker bar or torque wrench
Applicable Models:
986 Boxster (1997-04) 987 Boxster (2005-08)
Parts Required:
Wheel bearing
Hot Tip:
Put the bearing in the freeze prior to installation
Performance Gain:
Smooth driving, no wheel noise
Complementary Modification:
Replace CV joints and boots
This article is one in a series that have been released in conjunction with Wayne's new book, 101 Performance Projects for Your Porsche Boxster. The book contains 312 pages of full color projects detailing everything from performance mods to changing your brake pads. With more than 950+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any Boxster owner's collection. The book is currently available and in stock now. See The Official Book Website for more details.
Check out some other sample projects from the book:
Wheel bearing replacement has always been one of those tasks that I have found very difficult to explain in text. So, for this project, I have simply arranged them in order with captions. This first photo shows the wheel hub after the car has been raised (Pelican Technical Article: Jacking Up and Lifting the Boxster on Jack Stands), the caliper removed, and the brake disc removed as well (Pelican Technical Article: Brake Rotor Replacement). Also, before you raise the car off the ground, remove the center wheel hub cap (see Photo 3 of Pelican Technical Article: Tire and Wheel Sizing) and loosen the axle nut (blue arrow) with a very long breaker bar while the tire is still on the ground and car is in gear with the parking brake on. The photos for this project are of a front wheel bearing for a 996 Turbo, but the whole assembly is very similar to the Boxster setup.
If you didn't loosen up the axle nut while the car was still on the ground, you can use an impact tool to remove the nut (inset photo). This nut is on very tight, and you might have to work at it with the impact wrench in order to get the nut off.
Use a high quality ball joint removal tool (yellow arrow) to separate the ball joint from the wheel bearing carrier. When the joint is loose, use a pry bar (blue arrow) to push the control arm (green arrow) down while you lift up the carrier. Push the control arm out of the way and then you should be able to slide the carrier off of the shock. If you can't get deflect the control arm enough, then loosen the bolt at the other end of the control arm and you should be able to drop it down further. Don't retighten this bolt until the car is back on the ground in its fully weighted position. Remove the wheel speed sensor from the carrier when you have it on your bench.
Here's the axle with the carrier removed. Again, this is from a 4WD 996 Turbo, so there's a drive axle attached to this particular carrier. This design is very similar to the front and rear Boxster wheel carrier though. The toothed section of the axle generates a signal that is read by the wheel speed sensor that is mounted inside the carrier. If your CV joints need attention, or your rubber boot is ripped or damaged, then now would be the ideal time to replace it (see Pelican Technical Article: Replacing CV Joints and Boots / Axle Replacement).
The problem with this car was suspected to lie within the wheel bearing, but we weren't 100% sure. With the carrier out and on the bench, a simple spin of the bearing gave the answer: the bearing was toast. It felt like there was sand or something in the bearing and its rotation was rough, not smooth.
Positioning the wheel bearing carrier in Callas Rennsports' hydraulic press, we pushed out the inner hub (the part that the brake disc and wheel attaches to. As is common with wheel bearing replacements, the bearing itself fell apart and half of it remained attached to the hub (inset).
To clean up the hub, we used a standard bearing puller to remove the remains of the wheel bearing off of the hub. The inset photo shows the hub all cleaned up with all remnants of the old bearing removed.
When the hub was removed from the wheel bearing carrier, the bearing split into two parts: one that was stuck on the hub, and the remainder that was stuck inside the carrier. We went back to the press to remove the remains of the bearing. Remove the bearing retainer plate first (inset, lower right). With the bearing completely pressed out of the carrier, it should look like the inset photo in the lower left.
Here's a neat photo showing the physical damage on the worn out wheel bearing. The blue arrow shows pitting of the bearing surface: once this starts in a section of the bearing, it tends to continue and get worse. The bearing should be smooth like the section indicated by the purple arrow. The other half of the bearing is also showing the same deterioration and pitting. Although the seal on the bearing looked intact, this amount of damage leads me to believe there had been some type of contamination issue at play here.
Using the hydraulic press, you can easily install the new bearing. New bearings should be kept in the freezer right up until they are installed in the car (inset). If they are very cold, it will make pressing them into the wheel carrier much easier. During installation, press on the outer race of the bearing only: don't place any force on the inner race, as this can damage the bearing. Install the bearing with the numbers facing towards the wheel hub. Typically the red / orange seal goes towards the inside of the car.
With the new bearing installed in the wheel bearing carrier, it's time now to install the hub back into the inside race of the bearing. This is performed using a wheel bearing installation tool (blue arrow). Using a circular backing plate that is the same size as the inner race (yellow arrow), the tool pushes the hub inwards while compressing on the inner race. Crank down the bearing installation tool until the inside surface of the hub rests against the surface of the inner race of the bearing (green arrow). The inset photo in the lower left shows what the backside of the installed bearing / hub assembly should look like when the hub is fully installed. Test the hub on the bearing with a few test spins. Don't be alarmed if it doesn't spin too freely: new bearings are generally pretty stiff at first.
Reinstall the wheel bearing carrier back onto the car securing the ball join, shock tower, sway bar, tie rod, speed sensor connection, brake disc, brake caliper, and anything else you disconnected in the process. Tighten up the axle using a brand new nut.
With the car back on the ground, use a really big torque wrench to tighten up the axle nut. If you don't have a really big torque wrench, you can use a long breaker bar and your bodyweight to apply the torque. The torque value for this nut is 340 ft-lbs, so if you divide 340 by your weight (for example 200 lbs), you will need to stand on your breaker bar with your full weight, 1.7 ft (1 ft, 8 inches) away from the center of the wheel. Do this with the breaker bar perfectly parallel with the floor.
It's important to note that you do not always need to remove the wheel bearing carrier from the car in order to remove the wheel bearings. In the case of the 4WD Turbo, it was necessary because the axle was inserted in the inside of the carrier, and it was not possible to remove it without removing the carrier. In some cases, you can replace the wheel bearing with the carrier still installed in the car and avoid using the hydraulic press altogether. In this photo (and photo 17 and 18 as well), you can see part one of a bench demonstration of the process of pulling out the wheel hub using the tool. Put a backing plate on the inner race and use the tool to pull the hub out of the bearing (the bearing will break apart at this point).
Here's part two of the process of pulling the bearing using the tool. With a backing place the diameter of the outer race on the back side, the tool can simply pull the rest of the bearing out of the bore using the long center screw.
Part three of the process involves using the tool to press in the new bearing. Using a really big backing plate that compresses against the back of the aluminum wheel bearing carrier, the front part of the tool compresses the wheel bearing into place. Finally, the installation of the hub into the carrier is performed in the exact same manner as shown in Figure 13.
Comments: The black/brown side of the seal is magnetic and is the side ABS sensors read. Easy to check with a piece of steel. So normally, that would be the side that faces in and the orange side faces out. However there are two different methods ABS sensors reads wheel rotation, either by reading the magnetic strip off the bearing, or by a toothed wheel hub bolt. 2005 up cars don't have the toothed wheel and read the magnetic strip so it is important the brown side be in you you will get a PSM/ABS faulure light. On other years, with the toothed wheel 04 and earlier and all GT3s, the orientation doesn't matter
April 25, 2012
Joe Blow
Comments: In this article, you have the orange side out and the brown side down, does this matter?
April 23, 2012
Followup from the Pelican Staff: When researching this article for the 101 Projects book, we performed the replacement at Callas Rennsport and we came across this question. In the old days, it used to matter which way the bearing was installed (the lighter orange seal used to go to the inside of the bearing). But these days, it doesn't matter, and some of the bearings don't even come with different colored seals on them. We contacted the manufacturer just to confirm that the orientation no longer matters. This is what Tony Callas of Callas Rennsport has been teaching for the past several years in his master mechanic classes.
Now, on the newer cars that have integrated ABS sensor wheels into the bearing (2005 and later), you need to make sure that the sensor side goes next to the sensor itself. You need a special $15 magnetic tool to "see" through the seal and figure out that the sensor "wheel" is there. But these early 986 and 996 cars don't have them (only the newer cars, 987 and later). - Wayne at Pelican Parts
smohican
Comments: On my 986 rear wheel bearing, do I need to disconnect the axle from the Gear Box as the bentley manual recommends? Or can I remove the bearring carrier as you depict here in the process?
April 12, 2011
Followup from the Pelican Staff: Indeed, you should be able to simply remove the wheel carrier as detailed in this article. I think the Bentley manual assumes that you're trying to replace it with the carrier still installed. In that case, then yes, you would need to disconnect the axle, and then you would need to pull it out from the wheel carrier to remove the bearing. - Wayne at Pelican Parts
Check out some other sample projects from the book:
