cypermethrin

Ensuring that number 1 piston is at TDC

9 posts in this topic

I need to replace the gasket in my 300TDi brake servo vacuum pump.

Step 1 of this according to the 300TDi "Engine Overhaul manual" says " Ensure that number 1 piston is at TDC" then unbolt etc etc

Given that I only want to chnage the gasket and not take the head off - how can I do this ?? Or do it not need to !

Thanks

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OK so you peek in thro' the wading hole and look for the gap which marks TDC of piston 1

I understand there are two such holes in the flywheel (one small and one 3x ish bigger) - how do you know you have the right one ?

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A double check and some what better in that it confirms that you are both at TDC on number one and on the compression stroke, is as follows:

Remove the glow plug from no.1 cylinder.

Push some rolled up paper towel into the glow plug hole.

Turn the crank until the paper towel pops out, hitting you in the eye and permenantly blinding you.

You should then find you are at or around one of the holes in the flywheel. If not you can GENTLY insert a screw driver or simlilar into the glowplug hole and continue to turn the crank, CAREFULLY making sure the screw driver doesn't bind up, until the screw driver goes up and then starts to go down again on the piston stroke.

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I didn't when I did the same job on my 200tdi, just don;t move the Vac pump shaft or internals, it'll fit back in the same place, hasn't caused any problem on my 17 year old engine.

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What's wrong with taking the oil filler cap off and watching the rockers ?

That will only tell you roughly that you're at TDC, unless you know how many degrees before TDC both valves closed and the cam timing compared to crank.

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on a 300tdi ive never bothered with worrying about if cylinder 1 is at tdc, unbolt vacum pump & refit as required

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