M10 Timing Tensioner
If there is a loud rattle coming from the front of your M10 engine, it might be that the timing chain tensioner needs replacing. The tensioner uses oil pressure to tension the chain but lack of servicing and age can clog up the valve inside the tensioner, causing it not to function as it should.
Changing the tensioner is an hour job, requiring only a few simple tools.
Whilst it is possible to use 3/8” drive ratchets and sockets to do this job, it is much easier with a ¼” set with a 2” extension bar. Please note this is a recommended tool list, and not actually the exact tools you need. With a bit of common sense you can work out something with other tools. The socket sizes are the only thing to take real note of.
- ¼” drive ratchet
- 10mm socket
- 2” extension bar
- 19mm spanner
- ½” drive ratchet
- 30mm deep socket
- A small amount of engine oil (50-100ml)
- Small funnel
- Oil tray
- Brake cleaner or thinners
While the only part you technically need is the tensioner piston, there are a few other bits that can be done whilst doing this procedure. Whilst it isn’t necessary to change the gaskets, doing so may prevent future oil leaks. At a minimum it would be wise to get the first 4 items listed. And it feels nicer to do a proper job.
|Part||BMW Part Number|
|Tensioner plug washer||07119963355|
|Left upper timing chain cover gasket||11141727978|
|Right upper timing chain cover gasket||11141727979|
|Rocker cover gasket||11121734276|
- Timing chain tensioner plug – 40nm
- Upper timing chain bolts – 10nm
- Rocker cover nuts and bolts – 10nm
Left and right are referenced from the driver’s seat and not from the front of the car. Hopefully this picture will help you reference a few bits:
1. For the 316 carburetted models, it will be necessary to remove the air box and the pipe that runs from the air box to the headlight cover. These can be removed as one. Undo the wing nut or bolt on top of the air box and undo the clips around the edge. Under the lid in the centre of the box should be the two barrels of the carburettor, and around there three 10mm bolts holding the air box to the carb. Undo these. There should be another 10mm along the pipe leading the air box. Undo that and the headlight shield. You can now remove the air box and pipe. Be careful of the vacuum pipe that runs from the air box to the air heater flap in the pipe.
2. The next step is to the take the rocker cover off. This is done my removing the breather hose at the left rear of the cover, then undoing the seven 10mm nuts and bolts around the perimeter of the cover. Whilst it isn’t necessary, it’s good practice to slacken off the nuts in the centre and then work out to the edge, leaving the last one to undo the is the single bolt at the front of the cover. Take note of the earth strap at the right rear of the cover that attaches to the body, it will be important to reattach this at the end. It may take a gentle tap with a rubber mallet or a gentle pry with a flat blade screwdriver to get the rocker cover up if it hasn’t been off in a while. Be careful not to damage the mating faces or the gasket if you plan on reusing it.
3. You should now be looking at the camshaft and rockers of your engine. Here you can also catch your first glimpse of the timing chain, with the cam sprocket and chain appearing at the front of the engine. The next step is to remove the upper timing chain cover. This is held on with eight 10mm bolts. However a number of them are slightly tricky to get at due to the arrangement of the coolant hoses at the front of the engine and the water pump pulley. There are 3 on each side of the cover, two of which on the left side hold the bracket for the diagnostic plug on. Make note of where the bolts came from as some are slightly longer than others. Again, it may take some gentle persuasion with a rubber mallet or flat blade screwdriver to get the cover to move, and again, be careful of the mating surfaces and gasket.
4. You should now be looking at the top half of the timing chain. At the top should be the cam sprocket, and poking up from each side of the lower timing chain cover should be the plastic guide rails. Looking down, and at the right side of the lower timing chain cover should be a small well that is full of oil. This is where the tensioner resides. Our next task however is to time the engine up. Whilst this isn’t vital, again it’s good practice in case something does go wrong. To do this we just have to line up the mark on the front crank pulley with the mark on the cam sprocket. If you look at the front crank pulley from the left side of the car, you should be able to see a blunt, pointed bit of metal sticking out of the lower chain cover, about 1 o’clock from normal with the floor. Somewhere along the crank pulley will be a small notch. By turning the engine clockwise with a 30mm socket and ratchet (it is easier to turn the engine with the spark plugs removed) we should be able to line this notch up with the dimple of metal on the chain cover. Now turn your focus to the cam sprocket. On the sprocket there should be a dimple on one of the spokes leading from the centre. This should be at 6 o’clock. If it is at 12 o’clock, then the crank pulley needs to be turned another 360 degrees. If it is at any other position, then you haven’t lined up your crank pulley properly.
5. With the engine at TDC (top dead centre) on cylinder one, we can now do what we came here to do, and change the tensioner. This is achieved by undoing the 19mm tensioner plug on the right side of the engine. It is wise to place an oil pan under this plug, and let it cover the sump as well, as the oil has a tendency to run down the side of the cover and down the sump rather than just pour out. Slacken off the tensioner plug until it will move with your fingers. Be aware that this is spring loaded, and will shoot off unless you have a good grip on it. Get reading to catch the plug, washer, spring and a load of oil and undo it. A lot of the time the tensioner unit will stay inside the cover. It can be teased out by pushing the chain guide rail on the right side of the engine toward the outside.
6. With the tensioner piston removed, it’s worth noting how to check one. The system works with a one way valve inside the tensioner piston. Give the piston a shake and you should hear something rattling around inside it. This is the ball bearing that acts as the one way valve. If you can’t hear it then it’s probably stuck somewhere inside. The real way to check is to blow through the tensioner. In one direction you should be able to blow through, but the in the other direction you shouldn’t be able to. If you can blow through both ways or can’t blow through either, then it needs changing. Be aware that it’ll probably be full of oil before you go sticking it in your mouth though. If yours appears to be fine and you’re happy with that, then it’s up to you whether you want to change it or not.
7. With the tensioner out, and the well empty of oil, we can do some other work here. The gaskets for the upper timing chain cover may be those used out of the factory, and now you’ve disturbed them, probably need replacing. If the gaskets are stuck to the cover itself, then it’s a case of getting them off there. They’re most likely stuck to the engine block itself though. In this case, cover up the area leading down to the sump and oil well with some rag, and using a sharp blade, try to work the blade down and peel off the gasket. The rag is there to stop debris going into the engine. If any ends up in the tensioner oil well, it can be cleaned out with some brake cleaner or compressed air. The gasket may be ‘baked’ onto the block, in which case you’ll need to use some emery paper or gasket remover to get rid of it. With the gasket gone, use some medium grit sandpaper to clean up the mating faces, but don’t go too over the top. The same can be done with the rocket cover gasket, although these tend to remove themselves easily. Wipe the faces off with some brake cleaner and rag.
8. With the old gasket gone, we can now insert the new tensioner piston and bleed it. Note that it has two tabs of metal sticking out of one end. This goes in towards the engine, and the guide rail sits in between the two tabs of metal. It should be clear to see from the inside of the cover. Next, get your spring, plug and washer. The conical end of the spring should sit inside the plug, with the flat end inside the plunger. Take those three and insert them into the cavity, but just do up the plug one turn. Now take your funnel and oil, and fill up the well with oil. Once it is brimmed, hold the guide rail that sits against the tensioner piston, and slowly move it backwards and forwards, pushing the piston in and letting the spring push it out. When it moves out, a few bubbles should appear in the well. Keep doing this until oil starts to come out of the plug when you push the tensioner in. It may only take a few pumps, or it may take many. Top up with oil as necessary. This action bleeds the air out of the tensioner piston, which in turn allows it to function properly. With oil coming out of the plug, we can now do it up to the torque listed at the top of this article. Fill up the well again, to aid tensioning when you first start it up.
9. With the tensioner inserted and the gasket faces cleaned up, we can now reassemble the car. Go over the head gasket where it sticks out over the upper timing chain cover with some brake cleaner and a rag, and just do a quick once over of the other mating faces. Take your upper timing chain gaskets (they are sided so be aware) and one at a time, give them a film of grease on each side and stick them to the block, trying to line up the holes. With the gaskets in place, it is wise to place a line of silicone or instant gasket in the corner where the upper chain gaskets meet the head gasket, a common place for an oil leak to occur. Remember that the silicone won’t stick very well if the surfaces are covered in oil or grease so try to keep them as clean as you can. With that done, you can now re-attach the upper timing chain cover, and do the bolts up to the recommended torque. With the upper timing chain cover attached, the rocker cover can be re-attached. This would be an ideal time to your valve clearances now. With the rocker cover, again give it a film of grease on each side of the gasket and lay it on the head where it will only go one way. Then place the rocker cover back on and do up the nuts and bolts to the recommended torque. Again, try to work from the centre out towards the ends and remember to reattach the earth lead and the breather pipe.
10. The car should be ready to fire up now! Carburettor models should reattach their air box and pipe at this stage. With all the tools clear, and fingers out the way, fire the engine up. It should run nice and smooth, and hopefully quieter than before. If the engine is still making a large rattling noise, then it may be something else at fault. The easiest thing to check is your valve clearances, which have the same procedure as those for an M20 engine. It could also be that your cam sprocket is worn, or for the worst case, your chain and guides need replacing.
Original article by capnmchl