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  #1  
Old 05-07-2007, 05:32 PM
1990 300e 3L
 
Join Date: Apr 2007
Posts: 10
Calling for all valve/knock experience..

OK, have a knocking on my recent purchase 300e. Have read most of the engine knock threads and acted on them, but am still a little iffey on what might be the culprit.. hope somebody can help me out with some insight/experience.
The issue:
Engine has a knock, more present on idle, and on release from throttle. Absolutely is mechanical and within the block.
Noise does not start with start up of motor- there's about a 2-4 second delay from start-up to when it's present. I'm thinking a bearing, rod, or wrist pin would be there as soon as that cylinder spins.
Broomstick to ear test confirms its on cyl 6, though manifold makes it hard to guess where. Sound seems to be present through height of cylinder.
Exhaust has a noticeable mild hiccup every now and then. Very subtle.
All cyclinders were around 90psi on first crank, 120psi peak for compression, middle cylinders less so (70psi on first crank).
Knock is present,even when all other plug wires are pulled individually, greatly diminishes when numbers 6 plug wire is pulled.
No lack of power. am running 93 octane, and have run fuel injector cleaner and a batch of 104+ in it to clean out gunk. Have run a few tankfuls of fresh gas through it.
Pulled valve cover, and a quick glance didn't show any major issues.
At some point, PO suffered broken antifreeze holding tank, and looks to have baked head (from underneath, edges of head look amazingly clean in comparison to rest of engine)
I've driven this 30 miles at a crack about every day for the last week. Does not seem to be getting worse.

so, I've got three views on this so far:
1) Oil galley/etc. is blocked, run car w/ some marvel mystery fluid for a bit to clean out sludge and replace oil.
2) Broken valve spring. Causing hiccup in idle, and noise on head.
3) some combination of shaving head beyond clearance, valve striking cyclinder.
4) Valve adjustment, etc.
5) wrist pin or bearing.

Any thoughts? Anyone run into a similar situation? i'm also thinking about running some synthetic, and would welcome anyones views on which to run.
thanks.. !
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  #2  
Old 05-08-2007, 12:25 PM
david s poole
 
Join Date: Mar 2005
Location: dallas
Posts: 1,822
that is 103 engine.have you checked all of the bolts holding down the rocker assemblies?they are known to pull threads[they are steel and head is alu]and often need helicoiling.
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European Performance
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"Fortune favors the prepared mind"
1987 Mercedes Benz 420SEL
1988 Mercedes Benz 300TE (With new evaporator)
2000 Mercedes Benz C280
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  #3  
Old 05-08-2007, 04:42 PM
1990 300e 3L
 
Join Date: Apr 2007
Posts: 10
M103 knock

David, excellent idea.. didn't do more than give it a real quick once-over when the valve cover was pulled, I'll do that first chance. First time I've come across that..

regards, Jeremy
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1996 Saab 900S (196K), 1990 Mercedes 300e 3L (105K)
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  #4  
Old 01-18-2011, 10:30 AM
MeandMy300E
 
Join Date: Sep 2005
Location: Western MD
Posts: 28
So...what happened?

Did that fix your issue? I am experiencing something similar. It just started last night, and it sounds like a valve, but I have not gone as far as you have in investigating the engine. It runs fine, just a little knock, and the exhaust is a little louder.
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  #5  
Old 01-18-2011, 12:04 PM
TAG's Avatar
TAG TAG is offline
1987 300E
 
Join Date: May 2008
Location: Central NJ
Posts: 60
Whatever it is, don't let it go too long. I blew my head gasket and wasn't able to get it fixed right away. Here's a pic of one of my cam lobes as a result. They were all pretty much like that. Rocker arms were worn down too.
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Calling for all valve/knock experience..-tg-094-1.jpg  
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  #6  
Old 01-18-2011, 01:05 PM
MeandMy300E
 
Join Date: Sep 2005
Location: Western MD
Posts: 28
Wow!

Quote:
Originally Posted by TAG View Post
Whatever it is, don't let it go too long. I blew my head gasket and wasn't able to get it fixed right away. Here's a pic of one of my cam lobes as a result. They were all pretty much like that. Rocker arms were worn down too.
That looks pretty serious! I am going to go home after work tonight and take the valve cover off to see if I can determine the problem. I hope it is just a valve.
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  #7  
Old 01-18-2011, 02:06 PM
TAG's Avatar
TAG TAG is offline
1987 300E
 
Join Date: May 2008
Location: Central NJ
Posts: 60
Quote:
Originally Posted by Rage0582 View Post
That looks pretty serious! I am going to go home after work tonight and take the valve cover off to see if I can determine the problem. I hope it is just a valve.
My mechanic said that engine should not have even been running. But it started right up every morning .
A testament to its design I suppose.
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  #8  
Old 01-19-2011, 03:25 PM
MeandMy300E
 
Join Date: Sep 2005
Location: Western MD
Posts: 28
Solved

I think that I have solved the problem, I was simply low on oil. I added more oil, and the noise went away.
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  #9  
Old 01-22-2011, 09:43 PM
mak mak is offline
mark
 
Join Date: Jul 2006
Location: Westfeld .
Posts: 687
Good idea to drain and refresh the oil and filter ,i use the highly recommended chevron 15-40 Delo . Arguably the best oil for a 103 engine due to the ZDDP additive.
regards
mak
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  #10  
Old 01-24-2011, 06:07 PM
MeandMy300E
 
Join Date: Sep 2005
Location: Western MD
Posts: 28
ZDDP additive?

Quote:
Originally Posted by mak View Post
Good idea to drain and refresh the oil and filter ,i use the highly recommended chevron 15-40 Delo . Arguably the best oil for a 103 engine due to the ZDDP additive.
regards
mak
Sounds good, are there some advantages over Mobil 1 15w-50 (current oil)?
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