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

Have the vacuum pump replaced before you drive this any more. I have seen the bearings fall out and kill engines.

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Benzmac:
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Benzmac,

Have you ever heard the noise I described come from the vacuam pump?

Thanks a bunch,

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Larry Bible
'84 Euro 240D, 516K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

Benzmac,

Thanks for the response. I took the vacuam pump off last night. I now understand your response exactly. The bearing was very loose, about to fall out. It also explains the noise very well.

The vacuam pump was off my late engine and put onto the donor engine, which was an early '80 engine to allow clearance for the power steering belt and provide the correct connection to the vacuam line. Is the cam the same on both engines. Should I move the cam from the new style engine to the old to be compatible with the late pump?

As always, we very much appreciate your experience and expertise being shared on this forum.

Thanks and have a great day,


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Larry Bible
'84 Euro 240D, 516K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

So, what is the expected life for these vacuum pumps? I'm nowhere near LB's mileage, but I've already had to replace the pump diaphragm.

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Larry D
'76 240D @120k

Larry D,

I think the diaphragm probably deteriates with age, not mileage. The problem I experienced was mechanical wear, and gave me adequate warning. When it gets to the danger point that Benzmac warned about. You will be hearing a snapping noise from the pump.

Benzmac may tell us that he has seen them go without warning, but I guess I heard the warning, headed it and was lucky.

Good luck,

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Larry Bible
'84 Euro 240D, 516K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

I had to rebuild mine after 16 years and 150k miles.
Not terribly difficult, just time consuming.

-Larry

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03/83 300D
07/73 280