the "why" of top dead center (TDC) - Mercedes-Benz Forum

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post #1 of 3 (permalink) Old 10-14-2009, 08:33 AM Thread Starter
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the "why" of top dead center (TDC)

Hi, im currently planning to remove my waterpump from my 1983 380 sel.

Workshop manual says I need to remove the distributor first. I have looked thru this forum and found lots of info on what to do, my workshop manual also describes what to do. But I dont know why im supposed to do these things.

After some thought I reackon this is the "why":

When I rotate the engine by hand to TDC of 1st cylinder by looking at the TDC mark on the harmonic balancer (also called crank pulley damper, crankshaft damper, torsional damper, or vibration damper) the distributor rotor will spinn around and point to the first cylinder (roughly).
I will know this is ignition TDC (and not TDC for exhaust) because the distributor rotor is pointing to 1st cylinder(??).

When I pop off the distributor cap, the rotor should point to the 1st cylinder(?). I should then take a picture of the position of the rotor so that when i reinstall the distributor i will know whitch direction the rotor should point(??).

Am I, the lord of newbies, right??
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post #2 of 3 (permalink) Old 10-15-2009, 08:56 PM
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Use a paint pen or a marker to mark the rotor to the cap. Also mark the pulley to a mark on the timing cover to make you own marks if you really want to be safe. but the crank should not move during this repair. Mark the cap and rotor and you will be fine.
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post #3 of 3 (permalink) Old 10-16-2009, 01:12 AM
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Not trying to be a smart a** here. Just want to make sure you're clear on this. The rotor points to the number 1 spark plug wire on the distributor cap, not the physical number 1 cylinder on the engine.
I've seen people make this mistake.
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