TDC on 103 engine
 

I am in the process of a head gasket repair on a 103 engine, and this is my first time to R/R on the head gasket. The car is a 91 300E.

I am at the point to remove the chain tensioner and front cam cover. While I try to position no 1 cylinder to TDC. The making behind the harmonic balancer is not very clear. I can not see the mark.

What can I do to assure everything is align, before I proceed to remove the head.

Jack

Speed shops offer a TDC stop that screws in like a spark plug and has an adjustable bolt in the center that contacts the top of the piston. When you back out the adj bolt to where the piston will just turn, you then turn in to where you just stop the piston. Not sure if they make them in metric, but one can be made from an old plug. This is used when degreeing the camshaft.

Tim

Broke chain rail
 

I think I have the cam align correctly, but I broke the chain rail when I pull the pin out. Can I remove the head (I am waiting for the flywheel retaining lock), prior to removal of the lower timing cover.

Jack

I don't recall the M103 pulley pointer being difficult to locate or read. The marks on the pulley are not in the back but on the outside circumference where they are easiest to read.

Alternatively you can align the timing marks between the cam and first cam bearing tower. This should not be a problem since the guide you broke is probably the one on the tension side and the chain stays straight through that section.

You should be okay not setting the crank exactly to TDC. Both valves of the #1 cylinder closed is close enough. Once the head and chain tensioner are out you can spin the engine all you want to get the pulley mark to align perfectly. Make sure you hold the chain in tension. I think at this point it's safe to spin the engine backwards to get good alignment of the timing marks.

Sixto
95 S420
87 300SDL

Use some chalk to highlight the numbers and indentations.

Removed lower timing cover
 

Thank you for all the replies.

I removed the lower timing cover today. It was not too difficult, but the crank bolt was very tight. I will try to remove the head tomorrow morning.

Jack