I have a E430 2000 with 50k miles. My problem, I think is I noticed a knock when starting up in the morning, only and goes away with in a couple minutes. I was told it could br the Air Injector Pump. I use Mobil 1 0-40w full sythetic. Is this serious or common with this type of engine. I baby this engine and never drive it hard. Also how often do others change there oil.

You don't say where you're located, but here in the northeast, when the temperature goes down, the knocking complaints go up! Every year around this time, the "knocking when cold" complaints start to trickle in. Carbon build-up is by far the most common cause for this problem. Try some Techron fuel treatment. I'll probably go through a dozen or so cases of it before the winter's over. You'll probably have to treat two or three tanks of gas before the noise goes away completely.


P.S. The Air Injection Pump is known for making a high-pitched whining noise immediately following a cold start. If you still suspect that it's the cause of the knocking noise you can simply disconnect it before you start the engine. If the noise is still there, it's not the pump.

how do you disconnedt the air-injection pump? my 1997 e320 does the same knocking noise sometimes when the car is cold in the morning. i was starting to think it was connected more with the oil lifters. i was thinking of adding a engine cleaner product before doing the oil change, but i need your guys' advice first. is this recomendable? if so, what what be a good product, like bg or lucas? please help

i called the mb dealership and they told me that probably the cause of my engine knocking in cold mornings is the thickness of my oil. i'm running 15w40 (i live in south dakota currently, where it get's cold in the winter), and they said the oil is too thick for the lifters when it's cold. also they added that the noise would get worse, and that if i didn't change to a thinner oil (10w30 was suggestedi could cause damage to the engine. what they said doesn't seem that accurate. any suggestions?
also a few days ago i added the techron fuel injector cleaner to the tank. in case i add another one after this gas tank is finished, would that cause any damage to the plastic part of the injectors? i plan on changing the oil right after that. thank you.

I just added the Techron gas treatment and changed my oil with Mobil 1 0-40 syn.
I live in Chicao, Il USA, Again the noise only lasts a minute or two max. No oil consumpsion issues

MILO, let us know how things turn out, and remember, you may have to treat more than one tank of fuel.

After a tank of gas (1 bottle only) and changing the oil. The knocking noise has been reduced to a couple of seconds now. I am wondering since I only change my oil ever 10k, if the oil filter becomes clogged, not allowing a strong flow of oil a start up will this cause a problem? Also do you think I should throw in a second bottle of gas treatment.

dino changes 3k

synthetic changes 6k

that's the rule i live by.

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1989 300ce 129k
( facelifted front,updated tail lights, lowered suspension,bilstein sports, lorinser front spoiler, MOMO steering wheel, remus exhaust,stainless steel brake lines). (Gone)

1997 s320 154k (what a ride). Sold with 179k miles. Replaced with Hyundai Equus

1994 e320 Cabriolet 108k



1972 280se 4.5 153k Owned for 12 yrs, sorry I sold it


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Milo, I seriously doubt the oil filter gets clogged even with 10k mile oil changes; however, you may get some sludge build-up in the top of the engine if you frequently make short trips that don't allow the engine to achieve full operating temperature. Is there an oily gunk on the underside of the oil fill cap? Even with the newer engines and synthetic oil I change oil and filter every 7,500 miles. It's very affordable preventive maintenance.

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Fred Hoelzle

I did notice a little whitish oil gunk, whats that? but no build-up. I also looked down the throat of the oil cap and it looked very clean.

dam i couldnt imagine waiting 10k to change the oil .. sounds scary

The white stuff is moisture. If there's only a little don't worry about it. Frequent short trips, where the engine doesn't reach operating temperature will aggravate the situation. How's the cold engine knock?

The engine knock is gone, and also the whitish goo under the oil filler cap, after alonger road trip. Also does 10k seem that long between oil changes, it seems that after I changed my oil the knock almost total went away,? Note my oil levels are alway monitored and o.k. on my last oil change I used STP oil filter for the first time, not the best ones, I think.

I believe that the timing chain is tensioned by oil and at start up the pressure isn't there to make the chain tight, thus sloppy timing which has a cascading effect on the system. A good intake cleaning might help if the knocking is not timing related but my bet is on the timing chain.