What if you have what sounds to be an engine knock on a gasoline engine? Also as simple as an "injector"? Probably not - its never that simple with me. I know that sometimes at lower rpms (between 1500-2000 rpms) under acceleration I can hear an occasional knock from my car, but it has not gotten any worse. I know that my cam on the right side is probably worn, as I also have some clacky lifters on that side.

My grandfathers 90' Mazda 929 now has around 176K and if I recall, it has had a similar knock since (but louder) about 145K - still running.

Hopefully it is simply an injector issue with your car.

Hmm, it could very well be the vacuum pump, though this kind of failure is more common on the early W124's, but I'd still remove it and do an inspection. Did you try running the Diesel Purge like I recommended? It will save you time if it turns out it's not the vacuum pump.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

I'm going to get a vacuum pump gasket and remove/inspect the pump, etc. I'm also ordering some diesel purge and I'll give that a whirl. Hopefully one or both of these can help narrow down the problem. Thanks.

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83 300sd, 280K Blue/Blue Leather (~24mpg)
95 E300D, 150K Champaigne/Parchment(~33mpg)

Inspect that pump, make sure the bearings inside still roll nice and smooth ect.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

There is a tensioning device on the serpentine belt that attaches at the front of the engine. On my 1998 E300D TurboDiesel this device made some serious clanking noises until it was replaced. At one point, the valternator failed while my wife had the car and she took it to the dealership to have it fixed but that thing was intermittently locking up and at speed it made some pretty violent clanking and I believe finished off the tensioner. I presently have indications the engine mounting system is in need of attention (120k miles). The two together might have been even more alarming than just the tensioner.

I would not jump to a conclusion there is a serious internal engine problem until all the connected crap is checked out. So far the actual engine seems to be pretty robust. It is the electrical stuff that is so disheartening. Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

It looks like the vacuum pump is/was the problem.

I ordered some diesel purge to run through the injectors to see if it changed the noise in the slightest. So I ran some diesel purge through by filling a new main filter and replacing the old one.

I listened intently as the engine noise stayed the same...after about 5 minutes of this I let it idle while I went into the house for something. I came back out...and viola!!! no noise. The heart-warming sound of my OM606 was back.

At that point my happiness could only be expressed through interpretive dance!!!

So naturally I needed to proof this out. I decided to take her out for an easy spin to see if the results were indeed foolproof.
I eased out of the driveway and as I got to the slight slope at the end of the driveway I went to apply brakes...and the pedal is harder than chinese arithmetic. So it then clicked that the vacuum pump must have gave way and hence the brake pedal problem. So I very gently eased back up the driveway to park when lo and behold the engine would not shut down when the key was turned as normal (it's all coming into focus now). So I idled it down manually and now have the task of inspecting replacing the vacuum pump I THINK.

Question for the helpful members out there:
If I have this symptom already(loss of vacuum) and it was making a loud mechanical knocking noise previously...what are the chances I can rebuild this?
Isn't the rebuild just a diaphram replacement? This seemed like total failure??
Many thanks for the input received thus far.

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83 300sd, 280K Blue/Blue Leather (~24mpg)
95 E300D, 150K Champaigne/Parchment(~33mpg)

The 606 vac pump seems to be the same one MB used on the 603. So your only option if it failed is to replace the whole thing, then run about $300+$5 gasket. Super simple to change just unbolt the old one and bolt the new one on.

Of course it may be a leak, their is a test procedure for the pump.

You need a Mitty vac, what you do is hook it up to the pump and it is supposed to pull so much vac in so many seconds. The FSM will show this procedure for the 606.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I removed the old vacuum pump...In pieces!!
I pulled out what didn't come out with the pump/housing....the spring and the roller were separate. So after getting all the pieces out I could see I'm still missing part of the stirrup that went around the roller.
When the noise stopped the engine ran smooth, no sign of a problem.
So the question now is how big a liability is that missing piece I can't see/find?

I hate to ruin this engine by chancing it. What are the odds that the piece I'm missing is in a place to do no further harm? I don't know about the internal cavities of this engine so I have no idea how potentially dangerous to the engine this could be. Anyone else had this dilema?

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83 300sd, 280K Blue/Blue Leather (~24mpg)
95 E300D, 150K Champaigne/Parchment(~33mpg)

Ever wondered what the engine side of the vacuum pump operation looks like?...Here it is.

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83 300sd, 280K Blue/Blue Leather (~24mpg)
95 E300D, 150K Champaigne/Parchment(~33mpg)

I'll try again in a little while.

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83 300sd, 280K Blue/Blue Leather (~24mpg)
95 E300D, 150K Champaigne/Parchment(~33mpg)

Looks like it is time for you to start inspecting around the hole going into the engine and see if you can find the rest of ALL the pieces.

I would not turn the engine degree 1 until all pieces are accounted for.

You may have to check the pan for pieces too...

heh you really should NOT have driven/ran the car when you knew that your car was changing in the way it was shuttof off. Plenty of us have read the threads regarding the failure of the vac pump and what it can do to the eariler models...

It was trying to tell you what was wrong with it...but I guess now you get to fish out what is left

Clearly, the engine ran fine, even with the single piece disloged from the pump. Could it be sitting in a place where it will suddenly drop into the chain and take it out? Possibly, but unlikely. Either it's stuck in an oil passage or it has made it's way down into the pan.

Hopefully the piece was small enough that the latter scenario becomes the reality.

Two pictures..One shows the area where the vacuum pump attaches to the engine. The other shows the pieces I was able to retrieve. The piece I don't have is about an inch or so long..not very big but I'm sure it could do damage.

FYI...Once the engine started making noise I didn't drive it anymore. I did crank it in an effort to troubleshoot the problem. The pump finally broke and the noise went away. Either way...I need to find the other piece. I'll drop the pan soon and check it out.

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83 300sd, 280K Blue/Blue Leather (~24mpg)
95 E300D, 150K Champaigne/Parchment(~33mpg)

Cool...ya got lucky

Hope the other piece turns up...get to wear out the arms and drop the pan...so many damn screws

This is kinda scary that it can happen even on the OM606 engine. I thought this was limited to the OM603's. Definitely drop the oil pan and inspect thoroughly. Good luck finding that piece. Are all the ball bearings still in the vacuum pump?

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL