This article is one in a series that have been released in conjunction with Wayne's book, 101 Projects for Your Porsche 911. The book contains 240 pages of full color projects detailing everything from performance mods to changing your brake pads. With more than 650+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any Porsche 911 owner's collection. See The Official Book Website for more details.
One of the more frustrating parts that leak oil on the 911 are the oil return tubes. Years of heating and cooling, and expansion and contraction, can leave the rubber seals brittle and worn out. It is very common for them to leak oil right onto the heat exchangers, which results in both the car smoking when it's started, and also can result in smoke entering the passenger compartment through the heater system. The good news is that the tubes can easily be replaced with expandable replacements that don't require the removal of the engine.
How can you tell if your oil return tubes are leaking? Contrary to popular belief, the dry sump oil system of the 911 actually contains a large amount of oil in the sump when the engine is off. This oil can easily leak out of the bottom of the engine overnight, depositing a large amount of oil on the floor of your garage. In order to determine exactly where your oil leak is coming from, wash off the bottom of the motor, and then let it run for a while as you check where the oil leak is coming from. If the oil appears to be coming from the bottom of the oil return tubes on either the engine side or the outer cam tower side, then chances are that the seal has failed and needs to be replaced.
The process of replacing the oil return tubes is not very difficult, but it is a task that requires a significant amount of patience. It's also highly recommended that you have a spare oil return tube or two handy, as these are very easy to accidentally destroy during the installation process. If you are removing the heat exchangers, then I recommend that you replace the oil return tubes in pairs, either both left, or both right. They will eventually leak, and it's a wise idea to replace them now while you have access.
The first step is to remove your heat exchangers from the car. Check to make sure that this is necessary, as on some 911 models there exists enough room to perform this replacement without their removal. Removal of the heat exchangers in itself can be a very difficult step, especially if the bolts are frozen and stuck. Refer to Project 44 for more details on the safe removal of the heat exchangers. After the heat exchangers have been removed, it's a wise idea to empty the oil out of the car. This is not an absolutely vital step, but I recommend it in order to make the whole process just a bit cleaner.
Removal of the old tube is a somewhat easy, yet destructive process. Simply take a large pair of vise-grips and crush the old return tube in the middle. The ends should begin to pull out of the engine case and the cam towers. Compress and wiggle the old tube until you can get one end out free and clear. The other end of the tube should simply pull out. Make sure that you have a drip pan nearby, as there is a likelihood that at least some oil will spill out.
Now, move to your workbench, and assemble the parts of the new expandable tube. First take the circlip and slide it onto the longer tube. Slide it up past the grooves as shown the first photo of this project. Then place the two smaller seals on the two inner grooves of the larger oil return tube. Finally, place the two larger seals on the end of each tube. Prior to installing each of the four seals onto the tube, make sure that you wet them first with a little bit of clean motor oil, moly lube, or dielectric grease. This will help the seals seat properly, and should help prevent leaks. There are a few different types of tubes available. Installation instructions may vary slightly based on the particular type of tube that you choose to use.
When all the seals and the circlip have been installed properly, take the two tubes and slide them into each other. Crawl under the car and insert the end of the longer tube into the cam towers. The shorter tube should be placed into the engine case. The reasoning behind this is underscored by the fact that if the oil is going to leak, it's probably going to leak when the engine is warm, and the oil is thin and viscous. Because the oil returns from the cam towers back to the engine case, the tubes should be oriented in order to minimize the amount of contact that it will have with the two inner seals when the oil is warm.
The tube should now be ready to be expanded into place. The toughest part is getting a good grip on the oil return tubes. One idea is to use vise-grips or channel locks, but these sometimes have a habit of destroying the tubes. Another idea is to use a hose clamp. Simply tighten the clamp around the tube, and it should provide enough leverage for you to push the tube into its socket. Either way, be careful installing the tubes, as it is very easy to damage them.
After you get the first side installed, and the tube is firmly mounted in its hole, push on the opposite tube until you can slide the circlip into it's groove. When the circlip can fit entirely into the groove, then you know that the tube is completely expanded.
Refill the oil if you emptied it, and take the car out for a spin to check for oil leaks. If everything was followed correctly, there shouldn't be any leaks coming from the tubes. After installing the new tube, you may actually find that your leak was caused by something else. Take a look at Project 21 if this is indeed the case.
The expandable oil return tube kit is designed specifically to replace old, worn out tubes and seals that were installed the last time the motor was assembled. The kit contains the two rubber seals that fit on each end of the tube, an additional two seals that mate the tubes together, a large circlip, and the two tube halves. The tube is shown with the proper seals installed and the proper location of the circlip, prior to assembly.
The trick with getting the collapsible return tubes installed is getting each end compressed into its respective location, whether it be the engine case or the cam towers. The best method of achieving this is to use channel locks or a set of adjustable vise-grips, and tap the tube into the hole. Be gentle however, as too much force can dent and damage the tubes. The tube shown in this photo is manufactured by a different company than the one in the previous photo, but the installation process is very similar. While the tube is shown installed here, one of the installation problems is the difficulty involved with getting past exhaust pipes and other components. Sometimes it helps to remove the exhaust before replacing the tube.