Ready to pull OM603 head, how to set engine to TDC? - PeachParts Mercedes-Benz Forum

ah-kay · #1 08-19-2012, 06:40 PM

I am ready to pull the head on the wrecked engine. The oil pump chain snapped and the engine is stiff to turn. I want to see what the cylinders look like.

I have removed the timing chain guide pins, ready to pull the chain tensioner then the head. I need to set the engine to TDC. How do I do it? Have not done it before. Can I determine TDC from the cam positions?

sixto · #2 08-19-2012, 06:51 PM

Slip the pins back into place so the guide can help keep chain tension as you turn the engine. You're going for #1 TDC so keep an eye on the cam timing marks. You want the notch in the cam sprocket flange to be to the passenger side of the ridge in the first cam tower -

Then look at the 11 o'clock position of the crank damper. Identify the timing scale just behind the widest part of the damper. The scale is embossed on the rubber surface. An indicator floats over the scale. Align the center of the 0|T mark on the scale with the indicator; the pointy bit, not the circle of the indicator. The crank is at TDC and the cam is wherever chain wear puts it.

Focus on the lower right corner of this picture and you should see hash marks on the damper and the indicator. The circle thing is obscured by the water pump -

Sixto
87 300D

ROLLGUY · #3 08-19-2012, 06:51 PM

The crankshaft pulley should have marks on it, and a pointer on the case. The lobes on no 1 should be pointing up, with the crank at TDC. If the lobes are down, turn the crank 360 degrees.

ROLLGUY · #4 08-19-2012, 06:54 PM

Actually, if you are not going to put the head back on, it does not matter where the crank is. If it is too hard to turn, just pull the head and don't worry about where the timing is.

sixto · #5 08-19-2012, 07:01 PM

Quote:

Originally Posted by ROLLGUY

Actually, if you are not going to put the head back on, it does not matter where the crank is. If it is too hard to turn, just pull the head and don't worry about where the timing is.

There's a decision to be made with the 603. If you're removing the head with the cam in place, you need a long XZN bit to get to the head bolts covered by the cam towers, and you can remove the head with the crank at any position. If you're removing the cam before removing the head, the crank, or more relevantly the cam, has to be at #1 TDC so you can follow the cam tower loosening sequence. Or as some put it, you might end up with a DOHC engine in an unfortunate way. I prefer to remove the cam first because I don't like handling the head with some valves open.

Sixto
87 300D

sixto · #6 08-19-2012, 07:05 PM

The lower middle part of this picture shows how the scale is just behind the widest part of the damper. You can also see the part of the indicator unit with the circle, a hole really, floating over the widest part of the damper -

Sixto
87 300D

ah-kay · #7 08-19-2012, 08:49 PM

Thanks Sixto and Rich.

I need to digest the info as this is uncharted territories so be patient with me. Actually it took me a while to pull the guide pins. I buggered the top one, the pull bolt snapped inside the guide. I needed to drill a hole at the back and punched the top pin out. I pulled the lower one with no issues . I want to do this right for 2 reasons.

I have another SDL which I believe the head gasket is gone so this is a practice run, so to speak. I may also put this head back on if I overhaul the engine. I bought an engine hoist today and another 1987 W124 300D yesterday. I have a lot of options. It is just a matter of finding the time and inclination to do it. I have good engines and tranny around, the problem is they are in different cars.