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Discussion Starter #1
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Hi,

Recently after being away for 2 days, when I started my 1986 300E I noticed that it came up quite noisy (knocking) and with zero oil pressure for about 2-3 seconds. After this period oil press went up to the normal reading of 3 bars and everything seemed normal. Normally I start my car every day, so I never noticed this before.

Despite the age of my car and about 104.000+ miles, the engine is still in pretty good shape. I always use Mobil 1 synthetic oil, and just recently changed the oil and filter. BTW the problem I'm describing was first noted before the said oil and filter change.

I was reading some articles on this subject, and they seem to suggest that the oil in the filter slowly draws back into the engine when it is not running, so after a start it takes a few seconds for the pump to fill it up again. This makes perfect sense to me, but why does it happen? ... I figure Mercedes wouldn't let this pass by, it obviously is not very good to the engine, besides it sounded like someone was starting an old clunker.

One Mercedes Service Bulletin found at PartTrackers.com stated "If the little O-rings on the stem of the oil filter housing lid dry out or break, oil will drain out of the filter housing when the engine's shut down, and she'll knock for a few seconds at start up, which will eventually pound out the rods bearings. Don't mistake momentary (and perfectly normal) tick-ticking of the hydraulic valve tappets for this deeper sound."

So my question is: Should I be worried? (I'm already there), or is this really a simple matter of replacing a $1 part (o-rings) to prevent a catastrophic damage to the engine, and not to mention the stratospheric overhaul costs.

Has anyone experienced this same problem, and found the appropriate solution?

I wonder how do I change those o-rings, I guess they are under the filter, but I really can't recall seeing any other gaskets or seals besides the one that is attached to the oil filter, which by the way I did of course lubricate before installing it.

Any help will be greatly appreciated. I love my car and I'm kind of worried.

Thanks.

Alex
 

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Hi Alex,
The o-rings you are referring to are normally more of a problem with the diesel engines, as they would have a cartridge filter, as opposed to the spin-on filter on your 300e. Many oil filters have a check valve installed to keep the oil from draining back in the engine(it also doesn't make as big of mess when changing the filter). I don't know what type of filter you are using, but this could be part of the problem. I have experienced the ticking sound of the lifters, but not the knocking sound you describe, this may be something you want your local mechanic to check out. I am aware of some other engine noises you should be aware of(if not already), one is the shaft where your fan is mounted, if this bearing goes out, your fan will actually come loose from the motor. Another is the Idler Pulley on the right(passenger) side of your engine, another case of a bearing which will go bad. On a final note, I would think with only 104k miles, you would not be experiencing internal engine problems in the engine block itself. Please keep us posted on what you find.

Ken
 

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Discussion Starter #3
Hi Ken,

Thanks for taking the time to reply to my post, and for the tips. My car uses a spin-on type oil filter, and I always insist on only using a high quality brand.

I've been looking around for more info on my problem, and I found references that a worn-out Timing Chain Tensioner might be the cause of the knocking noise I hear when I start the engine after the car hasn't been used for a couple of days. In any case I still think that the oil pressure shouldn't take 2-3 seconds to come up to normal (any thoughts on that?), so the core of the problem may still be somewhere else.

With your permission, and for the benefit of other members following this post, I will quote the info bellow. Maybe it might be useful to someone else dealing with a similar problem.

I would also appreciate your feedback on this info, as you seem to be well informed on MB issues. I'm going to consult a mechanic tomorrow, and I'll keep you posted, but in any case I always welcome any extra input.

I found this article at
http://www.thebenzbin.com/mercedes-engine-parts.html

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Mercedes Engine Noises
Mercedes Timing Chain And Mercedes Timing Chain Tensioner

We can not stress enough the importance of changing the Mercedes timing chain, Mercedes timing chain tensioner and Mercedes timing chain guide rails every 100,000 miles. Failure of any of these components will, not might, cause considerable damage. It is our opinion that this is inexpensive maintenance to get you through the next 100,000 miles.

If you start your engine, after it sits all night, and you hear clatter which quickly subsides when you get oil pressure you probably are on borrowed time. Change the timing chain tensioner pronto regardless of how many miles on the engine.

The typical Mercedes timing chain tensioner applies tension to the chain via hydraulic pressure. The tensioner is supposed to hold this pressure after shut down. The noise you are hearing, on start up, is probably not lifters but the chain and the tensioner doing some wild gyrations behind the timing chain cover waiting for oil pressure to come to their aid. While those wild gyrations are occurring the plastic guides are taking a beating and will break and so on and so on. The end result is the valve timing becomes so adversely affected to the point where a piston hits a valve and now you have a real expensive mess.

The good news is that the Mercedes tensioners on most of the Mercedes engines are not difficult to change. They simply bolt right into the passenger side of the timing cover and timing cover removal is not necessary.
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If anybody has any comments, I'll certainly appreciate the feedback.

Thanks!

Alex
 

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excellent information, I just noticed this same noise in mine. at start-up. just orderd the tensioner. hopefully this will fix the problem if not Im sure it needed to be changed anyway.
thanks
Mark
 

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180,000 she runs great no problems what so ever but couple weeks ago I noticed that she knocked till it seemd oil got up to her lifters then quieted right down. from the tech page you posted it seems I might have misssed a big issue that would have turned into a bigger problem. but I also had my son change the oil around the same time and he might have missed placed the o-ring seal on the filter too. oil and filter is cheap will do that this weekend:)
 

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I have the same problem on my '92 300E 2.6. Ticking from the engine on a cold start for 2-3 seconds which goes away as soon as the oil pressure builds. I put in a new timing chain tensioner as suggested but the problem stayed.
Colin.
 
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