Took my 15 year old daughter out for some stick shift time yesterday. Got back and restarted the car to put it away. Heard a loud "snapping" noise. For lack of a better description, the snap sounded very much like a collapsed hydraulic lifter in a push rod V8, or like a spark arc. Said this to describe what I meant by "snap".

The noise sounds like it's from the power steering pump or vacuam pump area. It is a regular tempo sound which follows engine speed. I would guess that it is every engine revolution or two. But, I really don't think it's valve train related.

The vacuam pump has a half million miles on it.

Has anyone ever heard a vacuam pump fail in this way? Water pump? Timing chain or rails?

I plan on taking off the belts tonight, to see if the noise goes away, but I feel quite sure it won't. I will also take off the valve cover to see if there is anything obvious with the timing chain and components.

Any experiences with such noises and their associated failures would be appreciated.

I don't mind replacing whatever it is, the problem will be finding it.

I always try to walk back up the road and pick up the old part that fell off, so I know what to go buy.

Thanks for your help,


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Larry Bible
'84 Euro 240D, 516K miles
'88 300E 5 Speed
Over 800,000 miles in
Mercedes automobiles