shogun
01-04-2013, 07:39 AM
on a 6 cylinder M30 engine: If you need to remove your timing chain tensioner piston, I recommend replacing it. The reason for replacement is that if they have any wear they are less efficient, and can create noise from the timing chain.
On the big 6 cylinder engines, there is a small reservoir of oil in the upper right portion of the lower timing cover, where the tensioner piston enters, which is used to ensure the tensioner does not bleed down. The first thing to check when having tensioner problems is for leaks in this immediate area. If you find oil leaks in the area of the timing covers, repair these first.
Allow the car to sit overnight before replacing the tensioner piston. There are two reasons for
this, one is to allow the engine to cool, the second is to check the integrity of the aforementioned oil reservoir. You are going to have to remove the valve cover, so now is a great time to adjust your valves, a benefit of having the engine dead cold is better accuracy of the adjustment.
After removing the valve cover, place a rag over the A/C compressor and remove the 19mm cap over the tensioner piston. When you remove this, and slide the piston out, you should get about a table spoon full of oil flow out of the opening. If no oil comes out, you will need to replace your lower timing cover gaskets, or risk shortening the life of the tensioner dramatically. Once the old piston is out, install a new seal on the cap, insert the piston into the hole, followed by the spring, the narrow end of the spring goes into the back of the piston, then the cap. The spring is quite long and takes a little dexterity to get it into place and the cap done up. Be gently with the cap, do not use a tool on it until you have screwed it in by had for at least a quarter of the way, to prevent cross threading it.
Now comes the tricky part. you need to bleed the piston before it will work. This is why you have
removed the valve cover. Pour some oil down the right side of the engine directly above the tensioner piston, this will fill the reservoir in the top of the lower cover. Once the reservoir is full, use a long screwdriver to move the tensioner rail back and forth, this will expel the air from behind the tensioner piston, replacing it with oil. If you can see the reservoir, you will see the bubbles coming out. You may need to top off the oil once or twice during this procedure. You are finished when you can no longer move the rail in either direction. It should take less than a minute to achieve this.
Do not attempt to skip this procedure, it may take minutes of engine running to bleed this
piston, during which, severe damage to chain and rails could occur.
Replace the valve cover gasket and install the valve cover.
article from: Koala Motorsport Inc.* North East Ohio's ONLY Exclusive BMW Independent (http://koalamotorsport.com/)
Same timing chain tensioner mechanism applies to M70
When engine is running, I believe that a small internal oil passage will supply oil pressure to the little chamber behind the chain tensioner piston. The purpose of bleeding is like koalamotorsport describe above to get rid of air from that chamber.
On the big 6 cylinder engines, there is a small reservoir of oil in the upper right portion of the lower timing cover, where the tensioner piston enters, which is used to ensure the tensioner does not bleed down. The first thing to check when having tensioner problems is for leaks in this immediate area. If you find oil leaks in the area of the timing covers, repair these first.
Allow the car to sit overnight before replacing the tensioner piston. There are two reasons for
this, one is to allow the engine to cool, the second is to check the integrity of the aforementioned oil reservoir. You are going to have to remove the valve cover, so now is a great time to adjust your valves, a benefit of having the engine dead cold is better accuracy of the adjustment.
After removing the valve cover, place a rag over the A/C compressor and remove the 19mm cap over the tensioner piston. When you remove this, and slide the piston out, you should get about a table spoon full of oil flow out of the opening. If no oil comes out, you will need to replace your lower timing cover gaskets, or risk shortening the life of the tensioner dramatically. Once the old piston is out, install a new seal on the cap, insert the piston into the hole, followed by the spring, the narrow end of the spring goes into the back of the piston, then the cap. The spring is quite long and takes a little dexterity to get it into place and the cap done up. Be gently with the cap, do not use a tool on it until you have screwed it in by had for at least a quarter of the way, to prevent cross threading it.
Now comes the tricky part. you need to bleed the piston before it will work. This is why you have
removed the valve cover. Pour some oil down the right side of the engine directly above the tensioner piston, this will fill the reservoir in the top of the lower cover. Once the reservoir is full, use a long screwdriver to move the tensioner rail back and forth, this will expel the air from behind the tensioner piston, replacing it with oil. If you can see the reservoir, you will see the bubbles coming out. You may need to top off the oil once or twice during this procedure. You are finished when you can no longer move the rail in either direction. It should take less than a minute to achieve this.
Do not attempt to skip this procedure, it may take minutes of engine running to bleed this
piston, during which, severe damage to chain and rails could occur.
Replace the valve cover gasket and install the valve cover.
article from: Koala Motorsport Inc.* North East Ohio's ONLY Exclusive BMW Independent (http://koalamotorsport.com/)
Same timing chain tensioner mechanism applies to M70
When engine is running, I believe that a small internal oil passage will supply oil pressure to the little chamber behind the chain tensioner piston. The purpose of bleeding is like koalamotorsport describe above to get rid of air from that chamber.