Water-Cooled Rising Tide - Learn To Maintain your 996/997
The new wave is coming. For a long time, the air-cooled 911 has reigned supreme over desirability and collectability in the Porsche sphere. However, as the rising tide of the air-coolers raises all “ships” around it, the 996 and 997 have found themselves in a unique position between offering the uncompromising flat-six driving experience, whilst being affordable enough where even younger enthusiasts can get their piece of the 911 pie.
If you’re a new owner, thinking of getting into the water cooled 911 game, or even someone who bought their car new back in ’99, this article should provide a wealth of helpful info for making sure your 911 stays healthy for many miles to come.
IMS Bearing
Everyone who owns or is looking to buy a water-cooler has heard of the IMS bearing, but many people only know it as “that thing that totals your M96.” Let’s delve into what the IMS is, what to look for, and how to solve the issue it creates.
The IMS (intermediate shaft) is a central shaft in the M96 motor that runs the cam timing based on the rotation of the crankshaft. The IMS bearing, obviously, is the bearing that supports this system. The mechanical intention behind the IMS is to run the timing chain in a less wear prone more efficient way, but the early designs ran into many issues and have been a plague on the motor’s reputation. The M96 is an interference motor (valves and pistons occupy the same space at different times) meaning if your main mechanical timing component fails, your internals are toast.
This problem effects the 996.1/986.1 cars the worst, with the design improving every iteration. ’97-01 has the most struggles, ’02-05 is still at risk, and ’06-08 is the best as Porsche evolves to the M97, but still will eventually need a replacement. In 2009, Porsche introduced the MA101 motor to replace the outgoing M97. The MA101 eliminates the IMS completely, so all water-cooled motors after that point avoid the issue.
When buying any M96 or M97 car, see if the IMS has been completed already. Many cars have had this failure point serviced in the 15-25 years they’ve been on the road. If it hasn’t, plan your purchase around the idea of doing a full motor teardown. IMS service is always a good bargaining chip, whether you’re buying or selling.
If you end up needing to do an IMS service, there are a few different kits available from a few different companies. When replacing the clutch or rear main seal, it’s generally a good idea to do your IMS bearing to avoid future failures as it is a wear item. If you’re looking for an even more detailed breakdown of just the IMS, This article will answer your remaining questions.
Motor Mounts/Trans Mounts
Motor mounts are an item often overlooked in maintenance, as they rarely cause the car to go down completely and are easy to ignore if you don’t know the symptoms of bad mounts. However, a fresh set of mounts is one of the best things you can do for your car, especially now that the 996 and 997 are nearing 20 years in age. If you’ve got mysterious fluid leaking from the mounts, have excessive idle vibration, or hear a loud clunk under shifting or hard acceleration, it might be time to do the mounts.
Motor mounts do right what it says on the box, they mount the motor to your car. Maybe it’s easy to think “well my motor hasn’t fallen out so the mounts must be good” but like with most mechanical components of your car, it’s a lot more complicated than that.
The first big benefit of re-doing your motor mounts is comfort. If you’re someone who leans towards older vehicles, you may have more experience than not in cars with failing or collapsed motor mounts and may not even know what you’re missing out on. Replacing the mounts will give the car a completely smooth feeling idle, with low to minimal vibration in the cabin both at idle and at speed. It can completely change the comfort level of a car. Less vibration in the cabin also means fewer annoying creaks and clicks down the road as plastic components and switchgear are no longer being rattled free of their housings.
The second benefit of motor mounts is improved performance. As your motor creates torque, it wants to move around. A failed mount allows for a ton of excess movement. Excess movement is energy leaving the system, and results in worse power delivery overall.
The third and most important benefit is how other parts of your car benefit from your motor mounts being in good condition. As mentioned before, your car will have both less vibration and more isolation of movement. This will keep other parts from vibrating themselves loose or experiencing unnecessary wear. If the motor experiences high torque, which frankly these flat 6s have in spades, it can also severely damage parts that are hard mounted to both the motor and the body. The torsional force between the motor moving and the secondary hard mount point can bend, twist, or even tear other pieces inside the bay.
Water Pump and Cooling System
The M96 and M97 are known as the water pumpers for a reason. While they’re not Porsche’s first foray into water cooled motors, they are the first time a production flat 6 had coolant anywhere near it. Because of this, the pumps are not quite as reliable as the other more familiar aspects of the motor. It’s recommended that you replace the pump every 5ish years or 50,000 miles, whichever is sooner. M96 water pumps are less of a question of if it will fail, and more of a question of when.
When replacing the water pump itself, it’s important to think about the impeller on the pump. A lot of replacements are metal impeller, but the factory used a plastic impeller. Why was this? Well, the logic behind a plastic impeller is that if it does fail, only soft pieces of plastic will get inducted into the cooling system. A metal impeller is obviously less likely to fail than its plastic counterpart, but if it does fail the results can be catastrophic as metal shards could completely mechanically total your motor.
Past the pump itself, it’s good to do a coolant flush on these cars. The service interval on the coolant says it’s a lifetime thing, but with the M96’s tendency to leak from a failing pump, it’s likely the car has been low at least a few times in its life. Keeping up with coolant and water pumps is the key to keeping your water pumper pumping.
Caliper Restoration Service/Brake Maintenance
You knew it was coming, of course PMB would want to talk about brakes! Having your motor running and buttoned up with the IMS, Mounts, and Cooling refresh is all well and good, but if your brakes aren’t in adequate condition, you can only stop the car once…
As the 996 and 997s age, the time for brake caliper restoration comes upon them. The rubber seals installed in an early 996 caliper are now old enough to rent a car, and the seals in a 997 are at least old enough to vote. Rather than waiting for a possibly dangerous failure, it’s best to give those old seals a rest.
If you’re a DIYer, PMB Performance carries all the Brembo caliper bore seals and dust boots required to rebuild a Brembo caliper at home. Brembo seals are universal in terms of fitment, only differing in size. When you take your pistons out, measure the outer diameter of the piston and purchase accordingly. If you’d like to purchase some of these seals, they’re available by direct invoice either via email or over the phone (where, by the way, you can actually speak to a real person).
If pulling apart your calipers doesn’t sound like a fun way to spend your weekend, you can send them in to us for a full restoration. We’ll get them working like new and looking better than the day they left the Brembo factory, as we’re painting each caliper with individual attention rather than on an assembly line. Our restoration service comes with an industry unmatched 10-year full coverage warranty on the calipers, meaning if you have any trouble with them, you can send them back in for more service. If you’re looking to add some unique flare as well, custom colors, finishes, and logos are available.
Conclusion
Hopefully this article has put forward some valuable knowledge and decent guidance when it comes to keeping your 996 or 997 healthy and maintained. PMB Performance its 20th anniversary right now, and your car is likely around its 20th year on the road. Here’s to another 20!