A common failure point on these engines is a persistent oil leak on the top of the engine. It leaks from the rocker cover, then onto the exhaust manifolds and can make quite a mess.
It also leaks, in a lot of cases, more heavily, from the breather covers, which dont have gaskets and are sealed onto the rocker covers. These make a real mess and leak onto the coil packs, THEN onto the exhaust manifolds.
This problem affects all M113 engines so any 500 engined cars from 1996 up to 2006 ish. including 55 amg, kompressor or non kompressor. The steps to change are basically the same across the board. The procedure is nearly identical for M112 engines, but part numbers and breather hoses etc will be slightly different.
You will need :
2 Rocker cover gaskets, part numbers:
A113 0160 221
A113 0160 321
You wlil also need to replace 5 of the aluminium screws with updated steel ones as the old will snap if you try and re-use them.
These are part number N000912005010 and you will need 5. You will also need Loctite SI5980 Silicone Gasket Maker.
Remove engine covers and air boxes/hoses:
Remove the coil packs from both banks.
Note the copious amounts of oil covering my rocker covers.
Take note of the following locations. You will need to remove these brackets etc as they are held in place with the E10 bolts that hold on the rocker covers.
Front Left Vaccum valve has 2 E10 bolts holding it on , and also holds on a ground connection underneath it (its hidden by the rubber pipe).
There is a 10m bolt holding on the gearbox dipstick tube onto the rocker cover which needs to be removed.
This fuel pipe on the right hand side on the back had to be removed on mine. A fair amount of fuel did leak off so get a towel or rag handy.
Remove all the E10 bolts. There are longer ones on the top and shorter ones on the bottom, so no need to remember which ones go where.
Remove the breather hoses fron the covers on boths sides. On mine they where not brittle but where a bit spongy, I used a 14mm spanner to help them come off. I did not need to replace them, but do keep it in mind, should you need it.
They should then come off pretty easily. Do not try and pry with a screwdriver as they are brittle and will break easily.
You will be presented with this:
Ensure the engine is covered and bring the covers somewhere so you can work on them:
This is the boring boring BORING tedious bit. The resealing of the breather covers.
The channels have to be meticulously clean otherwise the new sealant wont cure properly and they will still leak. You must also ensure that all the screw whole and breather posts are completely clear so that they seal properly for the same reason and to ensure that you get no old selant falling into your engine and clogging oil ways.
You must clear out all of the grooves of the sealant surfaces on both covers. You must also ensure all the groves and the screw posts and breather posts have been cleared off too. This is a slow process as they do have to be completely clear of all old gasket material. I used a combination of brake cleaner, degreaser, and a small screwdriver. This is half of what I cleared out:
Afterwards, When the other half wasnt looking, I chucked the lot in the dishwasher
This is the resealing bit. I only took pictures of the smaller one as I didnt want the larger ones to cure before placing them together. WIS states to only use a 2mm bead, so less is more here. You also dont want bits of sealant coming off and ending up in the system.
Make sure you dont forget to seal the screw holes and the breather posts. Run the bead and then place the cover on in one motion. Use the new screws to secure the covers and tighten to 4nm.
Take the rocker covers back to the car with the new gaskets and fit them Place the gaskets into the rocker covers, then place the covers back onto the heads, ensure you havent trapped any wires, and that any brackets etc mentioned before are in the correct place. Re-connect the breather pipes back onto the freashly re-sealed breather covers. A bit of silicone spray helps them back on. If yours break or split replace them as they will cause an air leak and running problems.
Put the coil packs back on and give the the gasket/sealant a couple of hours to cure. Start the engine and check for leaks. If you have none, happy days, you are all done.