How often should I change the oil in my Porsche if I don t drive very much?
Even if you don’t drive very often and you’re not hitting the recommended mileage interval, it’s best to get your oil changed once a year. Your oil may be fine, but it’s the moisture in your engine that’s the real enemy.
One of the weaknesses identified in recent years by Porsche has been the intermediate shaft bearing (IMS bearing), which supports the intermediate shaft on the flywheel end of the motor.
Porsche designed these motors using a sealed ball bearing that is pressed into the intermediate shaft (Photo 12). These types of bearings are typically used in devices like copy machines and other machinery used in dry conditions. In theory, the area where Porsche designed the bearing to sit is supposed to be dry. However, after years of use within the engine, it would appear that oil and contaminants from the engine seep past the bearing seal, wash out the original lubricant, and become trapped inside. The result is that the bearing now operates in a less-than-ideal environment and begins to wear prematurely. When the bearing wears out, the timing chains on the engine may disengage, and the engine will quickly self-destruct. When the bearing does begin to deteriorate, foreign object debris from the bearing circulates throughout the engine, causing damage to other areas in the engine. This appears to be one of the most common failure mechanisms present with both the Boxster and 911 Carrera engine.
The center bolt that holds the entire assembly can also fail. If this bolt breaks, it will immediately allow the intermediate shaft to float, and the engine will skip timing. This will result in the complete destruction of the engine in a very short period of time (seconds). Typically, a deteriorating intermediate shaft bearing will also cause the center stud to weaken and break. The stud has a groove cut into it axially to allow for a sealing O-ring to seal to the outer cover. This groove causes a stress concentration to occur and promotes the failure of the stud. The solution is to pull out the bearing and replace the stud with a new one that is stronger and manufactured without any grooves (see a comparison of the old and new studs.
So how do you know if you have a problem? There are several warning signs. When you first start your car, you may hear a loud rattling noise that goes away after about 10 seconds or so. When you accelerate, you may also hear this noise too. This noise is the sound of the chains or the bearing rattling around in the engine because the bearing has deteriorated–the engine is soon on its way to skipping a tooth on the sprocket and costing you thousands of dollars. To detect the early stages of a failure, listen for a sound that is similar to what a throw-out bearing, water pump, or a belt idler pulley sounds like when the ball bearings begin to fail. If you have the car up in the air and running, you can listen carefully and you should be able to isolate the noise to the area of the IMS bearing (bottom rear of the engine, near where it mounts to the transmission), especially if you use a diagnostic stethoscope.
Signs of a failing IMS bearing can also be found by inspecting the oil filter. Shiny metallic debris from the balls used within the bearing itself may travel through the oil system and become trapped in the oil filter as well as small bits of black plastic from the seal on the bearing. During a routine clutch job, you can also simply remove the IMS cover and take a closer look at the bearing itself (lock and check the camshafts prior to removing the cover though–see instructions below). If the center shaft is wobbly, or the center of the bearing doesn’t spin freely, then it’s probably on its way to failure.
What Does a Bearing Failure Look Like?
If you take a look at Figure 1, you will see the remains of an intermediate shaft bearing from an engine with only 31,000 miles on it. Pulling off the intermediate shaft bearing cover revealed that the bearing had completely disintegrated and there wasn’t much left. This engine was running and the car was driving, but every few seconds it would make a horrible screeching noise. Sometimes it would run for quite a few minutes with no sound at all. Hard to believe, considering that the bearing was completely destroyed.
So what can you do with an engine that has had this much bearing damage? The engine was still running when I took the bearing out, so I know there didn’t appear to be any damage to the cylinder heads from the timing chains being out of sync. The oil filter appeared to do its job of blocking most of the bearing debris in the oil. The only thing that you can do when you have a situation like this is to clean everything out very carefully, replace the bearing, and button the engine back up.
What Can be Done to Fix or Prevent a Failure?
Luckily, there are a few solutions available. Firstly, I recommend that you change your oil every 5,000 miles or sooner and use a higher viscosity motor oil that has additional anti-wear additives. Use Porsche approved 5w40 viscosity motor oils, preferably one that carries an API SJ-SL rating. Use of a 0w40 viscosity should be limited to colder climates in winter months, where cold starts are regularly below freezing, for added start up protection. Also consider using an oil with more anti-wear additives (like Zn, P, or moly extreme). Recent regulatory changes in the United States have caused oil companies to revise their formulations of oil and reduce the amount of anti-wear components in them. The reasoning behind this is the belief that these components contribute to premature deterioration of the catalytic converters. I’m not so sure I agree with that premise however. The solution to this problem is to make sure that you run motor oil with the proper anti-wear formulations and change your oil often.
Also curious is the fact that cars that are driven tamely seem to have more problems than cars that are driven aggressively. 911 Carrera engines that are used at the track are known to have very few problems relating to the bearing, whereas 911s driven by “little old ladies” tend to show the most damage. The track-day Carrera bearing longevity may be explained by the fact that these cars often have their oil changed after every trip to the track.
The best solution to the problem is to replace the bearing prior to its failure.
Which Bearing is Inside Your Engine?
The first step in replacing the bearing is to figure out which one you have in your engine. There were three variations installed over the years. Early cars typically have a large double row bearing that has a snap clip inside the bearing. Porsche later went to a single-row bearing design when the timing chain design was modified (see Figure 7 for a comparison of the two). Then, around model year 2006, Porsche installed a third version that is not replaceable. The supposed cut-off on engine numbers is listed in the Porsche factory Technical Bulletins, but unfortunately, these numbers are not 100 percent accurate, so you need to look at the bearing housing on your engine in order to be 100 percent sure as to which bearing you have installed.
LN Engineering Retrofit Kit
The LN Engineering IMS Retrofit kit is also an easy-to-install upgrade kit that can be installed with the engine still in the car and provides almost bulletproof reliability to this critical component. This kit costs about $600 and is available online from PelicanParts.com. The upgrade kit incorporates a custom ceramic hybrid bearing (see Figure 5), featuring precision Japanese-made tool steel races and genuine USA-made Timken sintered silicon nitride ultra-low friction roller balls. This bearing, combined with a beefier center stud and a custom-machined housing, ensures that the IMS problems inherent in the stock design are mitigated. The engine can be upgraded during a routine clutch job and is fairly easy to install thanks to the installation tools designed by LN Engineering specifically for this task.
Which Kit to Use?
I designed the Pelican Parts replacement bearing kit in order to fill a gap within the do-it-yourself (DIY) market. This kit is designed to replace the factory bearing with a very similarly manufactured bearing (with an improved seal and updated center bolt). I recommend that the bearing be swapped out each time a clutch replacement is performed (30,000-45,000 miles). The outer seal is not removed on the kit, instead an improved seal is installed, which should offer longer life than the factory original. Replacement bearings, O-rings, and parts will be available for customers who have already performed the swap at least once and already have the tools, spacers, and the improved center bolt. The Pelican Parts kit uses the stock intermediate shaft bearing cover as a way to reduce the total cost of the kit, though we recommend if you have the older style single round gasket cover you replace this with the newer version from Porsche which is less likely leak. While we include both style of gaskets in the kit including a replacement gasket for the older style covers, Porsche no longer supports this part.
The LN Engineering retrofit kit contains a stronger-than-stock center stud, a custom machined intermediate shaft end cover, and a special, custom-manufactured ceramic bearing, which is very expensive, but has much longer life under harsh conditions. The LN Engineering kit is considered to be the more robust kit and is designed primarily for shops that are installing the retrofit and need that extra guarantee for their customers. The extended-life ceramic bearing is only available at this time with the LN Engineering kit, and its inclusion is responsible for a large portion of the cost difference between the two kits.
Porsche Ceramic Composite Brakes
Some of you may not even know if you have Porsche Ceramic Composite Brakes (PCCB), so if you don’t go out and look for this:
If you have these yellow brake calipers on your Porsche then you have Porsche Ceramic Composite Brakes. Next you say so what and what are they?
Most brake systems on most vehicles on the road today use brake discs made of cast iron. Porsche does also, and those brakes are some of the most exceptional brakes made for any vehicle, period. But what Porsche along with many high performance auto manufacturers also offer are very advanced Ceramic Composite Brakes.
Porsche Ceramic Composite Brakes (PCCB) use a cross-drilled, carbon fiber reinforced ceramic disc with special composite pads. During manufacture, the basic disc molding (made from a carbon-fiber and polymer mix) is silicated (made into a silicate compound) in a special high-vacuum process. Like Porsche’s conventional discs, the PCCB parts are cross-drilled and directionally vented as shown in this cutaway illustration.
A PCCB brake disc weighs 50% less than its cast-iron counterpart despite considerably larger dimensions.
Like a competition-bred conventional system, the ceramic outer disc is mated to a steel inner “hat.” PCCB brakes use specially developed six-piston calipers on the front and four-piston calipers on the rear.
The PCCB pads offer a high coefficient of friction for moderate pedal efforts and unusual consistency of friction characteristics across a wider range of operating temperatures than is available with Porsche’s conventional brakes. Several different pad compounds are available for street and various levels of track use.
Another key benefit of PCCB is its exceptional durability. While the actual rate of wear on all brake components–particularly pads and discs–is entirely dependent on individual driving style and vehicle usage, comparison testing reveals a much longer life expectancy with PCCB than with conventional braking systems; as long as 160,000 miles or more under normal driving conditions. It is important to note that racing and other extreme driving can significantly reduce the life expectancy of any vehicle component. After any driving event, have the vehicle, including all PCCB components, thoroughly checked and replaced as necessary.
PCCB systems are expensive to order for a new Porsche or to retrofit. By far the most cost effective way to get them is to simply check the option box when ordering your Porsche. The price of all the individual parts comes to near $25,000, but some the upgrade kits can be cheaper, which is still considerably more than the option cost. On the Cayman and Boxster the cost for PCCB is $8000, and on all the other models it costs $9000 to order.
The $8000 or $9000 question is whether they are worth the extra money? The online Porsche forums have a wealth of information on this topic as well as some spirited debates. Most seem to say that the PCCB systems are better for road driving than for track driving. Clearly, even with the advantages in durability and fuel economy, one doesn’t choose PCCB in order to save money. This is one case where it will really pay off to do your homework if you are considering ordering a new Porsche with PCCB.
Oh, and if you went out to the garage or driveway and found out that you do in fact have PCCB on your existing Porsche, you now know you have great brakes that will last you a long time, but know that when they do wear out, it will be an expensive repair bill.