911 Oil Return Tube
Replacement

Difficulty Level 3

Difficulty scale:
Adding air to your tires is level one
Rebuilding a 911 Motor is level ten

Figure 1:
Huge Oil Leak

     The next day, I went out to my driveway to get my morning newspaper. Needless to say, I was astonished when I saw a long stream of oil coming from underneath the garage door. I opened the garage, and my garage floor looked like it would be a good candidate for an EPA Superfund clean-up site! There was a puddle of oil about 3 feet wide, and about six feet long, and it had somehow migrated underneath the garage door and down the driveway.   This puddle is sadly shown in Figure 1.

     Seeing how there was so much oil there, I really couldn’t easily figure out where it was all coming from. I originally thought that the oil was leaking from my oil tank lines. This line always has oil in it under slight pressure from the weight of the oil. I figured that this slow leak had to be from this line. I was wrong.

     I didn’t suspect the oil return tube at first, because I was most familiar with the 914 dry sump motor, which doesn’t fill up the oil return tubes when the car is sitting idle. However, after consultation with a few other people, I soon learned that the oil return tube is often filled with oil when the car is sitting idle. The oil sump on the bottom of the 911 motor overflows into these tubes. If there is a small leak in one of the tubes, or past one of the seals, then you might find yourself losing oil at a tremendous rate overnight.

     The purpose of these tubes is to return oil flow back to the sump at the bottom of the 911 motor. No oil flows through them at very high pressure. They simply collect the oil that flows back from the heads.

Figure 3:
Expandable Oil Return Tube Kit

     The first step in beginning the replacement process is to make sure you’ve identified exactly where the leak is coming from. You would hate to do this job, and then figure out that the oil is coming from somewhere else. Before you begin, take your car to a self-serve car wash that allows you to wash your engine. Please don’t wash the engine in the street, as this will hurt the environment. Drive the car back to your garage and immediately look underneath. You should be able to figure out exactly where all the oil is coming from. If it is coming from the oil return tube, then there will be oil on the ground right below the tube.

     The next step is to empty the oil from the car. You don’t absolutely need to empty the oil, but it will make the job a little bit neater. When you remove the oil return tube, a small stream of oil will run out, so make sure that you have a drip pan to catch the oil.

Figure 5:
Placing Circlip on Tube

Figure 6:
Assembled Expandable Oil Return Tube

Figure 7:
Removing Old Oil Return Tube

Figure 8:
Oil Return Tube Removed

Figure 9:
Inserting one-half of Tube into Engine Case

     Now, push on the little circlip that comes with the tube. This rather large clip prevents the tube from coming apart when installed in your car. Use a pair of needle-nose pliers to make sure that you put the clip on without damaging both the clip or the tube, as shown in Figure 5. Now, insert the smaller tube into the larger one. It should slide in quite easily. Note that if you are not careful while installing the tube, you can bend it, and then it will be almost impossible to expand when you’re underneath the car.  The assembled tube should now resemble Figure 6.

     Now, you need to remove the old tube. On some cars, you may need to remove the heat exchangers or headers to gain access to a particular oil return tube.  Be careful when pulling the heat exchangers off of the heads as you don't want to accidentally remove the head studs.  The best method for removing the oil return tube is to just take a pair of vise grips and crush the tube until it’s bent. Then twist the tube with the vise grips until the tube comes out of one end, as shown in Figure 7. If the seals are truly old, then the tube should come out easily. Once you get the tube out, if you didn’t empty the oil out of the engine, it will begin to flow a little. Make sure that you have a drip pan ready.  Figure 8 shows the oil dripping out of the engine case where the tube used to attach to.

     Insertion of the expandable tube is straightforward, although not too easy. Begin by placing one end of the tube into either the main engine case or the port nearest to the heads, as shown in Figure 9. Depending upon your leverage, or your particular car, you will have to figure out which end is the best to start with. Make sure that you place the smaller end of the tube nearest to the heads. (the larger of the two tubes should go into the heads).  The reasoning behind this is that if the tubes are ever going to leak, they will probably leak worse when the engine is warm and the oil is hot and very thin. When the engine is running, the oil will be flowing from the heads to the main engine case. By placing the smaller tube within the bigger one, the oil flow will not press up against the seals. It’s not a very big deal as to which way it goes in, but it may make a difference many years down the road when the seals begin to deteriorate.

     After you have one side of the tube inserted into the case, then you need to expand the tube to reach the other side. There are a few ways of doing this, and none of them work too well. I would suggest holding one end of the tube lightly with a set of vise-grips, while pushing against one end of the tube with a screwdriver. Be careful while expanding the tube. If you damage it, then it will be almost impossible to expand the tube under the car. For this technical article, I ended up destroying the first one I had getting it in there. You might want to order two as cheap insurance. Once you remove the old one, you can’t put it back in. It would be wise to have an extra tube on hand, so that your car is not sitting idle, waiting for one to be shipped next day air by Pelican Parts.

     After you have the tube expanded and the seals are firmly mounted on both ends, then slide the circlip down until it reaches it’s groove, securing it under the car. Use the needle-nose pliers again to avoid damaging the tube.

     After you have installed the tube, check to make sure that everything is seated correctly. There should, of course, be no oil leaking out of the tube. After the tube is installed, then reinstall your heat exchangers or headers if you had to remove them to gain access. Use new copper exhaust gaskets between the heads and the pipes. Reinstall your muffler if you had to remove it too, using this opportunity to install new gaskets as well.

     Well, that about sums it up. Hopefully  your car will no longer be leaking down the driveway. If you have any questions, feel free to ask.  Remember that Pelican Parts can provide you with all the parts that you need for any job!  Your continued support will guarantee that technical articles like this one will continue.  Please check out our ordering page for more information on our on-line catalog and on ordering new and used parts from us.

Bill Norwood adds:

Greetings,

I just finished installing new replacement oil return tubes on my 87 Targa as as per your bulletin. I replaced all without dropping the heat exchanger. In fact the one that seemed to be the hardest was the easiest. Rather than use a vise grip to get leverage on the slippery little devils, I put hose clamps on the ends of each. The hose clamps make great places on which to use a pry bar to gain the required leverage. The clamps don't damage the tubes and they come right off. A short handled expander tool for the C rings Helps too. Now if my creeper only had brakes.

Drivin' the Poorsche with thanks to Pelican Parts.

Bill Norwood  Gildedgallery@prodigy.net

JPF (frickjp@theoffice.net) adds:

I saw your little tech session on replacing the oil return tubes on the 911. Nice touch, but I've found over the years two things that make life easier. Silicone paste instead of engine oil, Sil-Glyde from NAPA is cheap. The second is take that circlip and throw it out. I use gaiter spring from large Ford Spring-Lok A/C connections, available everywhere. Roll the gaiter spring up the tube, install it, slides righ in with Silicone paste for lube, and roll the gaiter spring into the groove with 1 finger. Beats the circlip method hands down. 4 tubes take about 15 extra minutes during an oil change.

Zakcruz@aol.com adds:

I just replaced my return tubes on my 84 911 using the tech article and the added suggestions from Bill and JPF.  I too replaced all 4 without removing the heat exchanger.   3 tubes were leaking, but I wanted a matching set.  First, I crushed the old tubes (1 at a time) and used tin snips to cut them.

This made it easier to remove especially the ones under the exchangers.  I used the Sil-Glyde.  I spent a little too much time looking for the gaiter spring from large Ford Spring-Lok A/C connect.   After visiting 4 auto-parts stores, Napa said they could get them the following morning but for $14 a piece.  I decided to go with the circlip.

The hose clamp suggestion worked great, although I only needed one clamp which I put on the thicker end which was the end that goes toward the crankcase.

The tool I could NOT have accomplished this with, is the expander tool.  At Ace Hardware, they sell a Snap Ring Plier Set for about $12.  It includes expander heads at a straight angle, 45 degrees and 90 degrees.   I used all 3 to move the circlip down the tube.  It almost seems like they made the set specifically for this job.