964 - Chain Tensioner Cover
Replacing the Upper Chain Tensioner Cover Gasket
What is the Chain Tensioner Cover?
Their are two Chain Tensioners needed to keep the proper tension on the Cam Chain. There is one on the drivers (left) side, here called the upper, and one the other (right) side here called the lower. There is an external cover over the tensioner spring that appears to serve as a bridge to bring oil from the sides into the spring area. I will cover replacement of the upper gasket here, but my assumption is that replacing the lower one would be similar. In fact it may be easier due to better access. The tensioner works by using a large spring supplemented by the pressure of the oil. Since this area is under pressure the seal between the cover and the engine can leak. The gasket, shown below, is made of aluminum with rubber integral o-rings. The o-rings can degrade over time causing some weeping of oil in this area.
These tools will be needed:
- 10mm socket
- 6" extension
- Socket wrench (I have one with a joint at the head and that helped a lot, but you could do it with a regular one, short strokes help)
- Torque wrench
- Grabber tool to hold the nuts in place and pick up dropped ones. I have one that is a little over a foot long that has four prongs on the end that are extended by a plunger on the other end. Without this it would have been very difficult. I would have removed the distributor for access.
How to replace the gasket
- It is best to do this on a cold engine. There will be less oil to come out that way.
- Open the engine compartment lid
- Locate the chain tensioner cover on the left side of the engine under the distributor. See picture above.
- Yes, it is tight in there and access would be easier if you removed the distributor or at least the cap and wires. I was able to do it with them in place.
- Use the 10mm socket and the extension to loosen the nuts holding the cover. When they are off you may drop them but they can't really go anywhere and that is why you have the grabber.
- Remember how I mentioned the spring? Well this is where it starts to push up. Once you have one side up it will want to pop off the cover. It might be a good idea to loosen one bolt some, then the other, and then back. I sort of did this and it worked out ok. Beneath the nut there is a thick crush washer. I reused mine, but it might be good to replace it and the nut as well.
- Eventually the nuts and washers will be off and the cover will have sprung up. There will be a very small amount of oil that will come out, but not enough to make a mess.
- As they say, assembly is the reverse, but it isn't that easy.
- First take off the old gasket. Mine came right off. Then making sure the area and the new gasket is clean, put it in. The holes without the rubber go over the studs. I checked the factory manual and they didn't specify a sealant so I didn't use any.
- Place the cover back. Remember that spring? Well this is where it starts to cause trouble. It will push against the cover making it very difficult for you to get enough room to get the nuts on. Having limited access with the distributor is beginning to look like a bad idea.
- Here is what I did. I pushed the cover down on the left side because it seemed to have the best access. I could get it down and still over the right side. Then I could use the grabber with the nut on it to carefully screw the nut in a few turns. This is without the washer since that takes up too much room. So with my right arm I held the cover down and with my left I threaded the nut on while attached to the grabber. Once I had enough threads on that so it would stay I detached it from the grabber and got the socket on the extension (placed nearby) and threaded it down, while still holding it down on the right. I got it down enough that on the right side there were enough threads that the washer and nut would fit. Now it gets easy. You put the washer on the right side and use the grabber to start threading the nut on. Then the socket and extension. Then you can tighten it all the way, but don't do the final tightening yet. Turn to the other side, undo the nut, drop it (you will), then put the washer on (using the grabber), then using the grabber start to thread the nut. Get the extension and socket and tighten the nuts. Once snug you can use the torque wrench to get them at 7.5 ft/lbs or 10 NM. If you don't have a torque wrench this really isn't that tight. If you have a short handled wrench it would be about as tight as you can comfortably do it.
- Ok, now the fun part. Remember the spring? Remember the oil under pressure? Well you just removed some of that oil and let air in, didn't you? Here is what happened to me. I had this in the back of my mind, waiting for some horrible chain noise. I started the car carefully and I heard the rattle. I instantly shut it down, took the time to visualize towing, huge repair bill, etc. Then I started it again carefully. Well the pressure was there and it started up normally and was fine. I went back and looked for leaks and it was dry.
I think what happened is that by removing the cover you introduce air into the system. So when the oil starts flowing you have trapped air in there that has to work itself out, you need to bleed the system. This is just a guess however. If someone can provide a way around the pressurization issue enter it here. I'd appreciate comments. I suppose I could have manually turned the engine? It seems similar to what happens at an oil change with that momentary low pressure. Maybe there isn't anything you can do, and it doesn't seem to cause any damage. I don't want to scare anyone away, this project is very doable and had I known what to expect it would have been much easier for me. In all I did it in less than an hour and that was taking my time. Sorry there aren't more pictures, but I was oily and in no mood to take any. There are other pictures on the web of this area though but I don't think more pictures would matter since much of this is by feel anyway.
Article Credit : Mark Schettenhelm