M104 timing
 

I did a head gasket repair on a e320 1994 M104 and I am at the point of puting the cahin back. I did mess up the marks on the chain and gears and I an stuck. Please help. I did try to search the forum but most of the links on the previous posts are not active.

Timing marks!
 

Most people think that the M104 cam sprockets have no marks but in a way they acutally do. There are holes on the backside of the sprockets where you insert a pin or allen key so that the hole is flush with the valve cover machined surface. Facing the engine fron the front the proper reference would be the exhaust cam hole @ 9 o'clock and the intake cam hole @ 3 o'clock keeping in mind that these holes are on the backside of the cam sprockets. This information is available in ALLDATA.
Once again set the pins to reference the cam sprockets with the crank at TDC. Also make sure that the camshaft timing advance is contacting from the direction of rotation. In other words the intake cam is turned so that the variable valve timing slot is being pulled in the direction of engine rotation which in this engine is clockwise. Now remove the pins and turn the engine clockwise to take up any slack in the chain. Always do this before installing your timiing chain tensioner. Failure to do so can break the timing cover when screwing in the tensioner.Turn the usual 2 rotaions and double check that all is lined up properly. I hope this helps! Good luck!:)

http://www.peachparts.com/Wikka/M104HeadGasket

Pay special attention the section on the chain tensioner reset procedure..see cams snap right in half b/c guys do not reset the tensioner ratchet lock.
BIG $$$$ MISTAKE.

Thanks for the excellent link Arthur. My engine is back together and running beautifully. It worked perfect for the first time. No more leaks.
Now I have to tell you my part of the story. The head gasket was done 40k miles ago by the previous owner. but the last two bolts by the firewall were not torqued properly. They almost came out without any effort. The head was properly done at that time and a new chain and guide rails were installed. So my job was just to remove the old gasket clean the block and the head and reinstall the new gasket.I assume that was the reason for antifreeze leaking badly.
I did a 250miles stretch and 50 miles in the city and the cooling system works excellent. Except a hose clamp that I over tight and it snapped loosing few quarters of antifreeze and the nipples from the manifold that brooked.
Thanks for excellent support guys.

Question!!!
 

Alright question time----- I am in the process of removing the head on a 1994 c280, I read the articles mentioned here. Now---why are we painting the chain and sprocket at TDC if when we reassemble we use the dowel pins for cam timing?


When we marked the position of the chain at TDC and then looked for the dowel holes they are not level with the surface of the head, which is where they need to be when reassembling, which will make our paint marks obsolete. I hope someone has experienced this also and can shed some more light. Thanks for any advice!!

bump for reply.

Maybe the chain is stretched . You have to align the 4mm drill bits with the surface of the head. then put the engine on TDC. Rotate the intake cam all the way to the right until it stops. Then install the chain starting from the right side.
Very important: Remove the chain tensioner and reassemble it accordingly to the DIY article.
You can email me directly with questions.

Thanks radunegru I sent you an email.


Why do we paint marks if they are not used for reassembly?


Thank you.

I completely ignored the paint marks. As long as the two halls are even with the head and tho TDC is on . Maybe your chain is stretched.