Mercedes-Benz Forum - View Single Post - M103 Rough idle and vacuum leak
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post #112 of (permalink) Old 01-07-2018, 05:47 PM
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Date registered: Feb 2015
Vehicle: 1989 300SE (Mitzi); 2003 CLK 430 cabrio (Clifford)
Location: Southern California, USA
Posts: 442
Mentioned: 4 Post(s)
Quoted: 133 Post(s)
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Originally Posted by H.D. View Post
That‘s the right expression … ‘potentially‘ worn camshaft and rocker arm(s). The part beside the camshaft is one of the rocker arms (not a lifter).
So, before you try to find suitable replacement parts at junkyards, I recommend both of you to first check the installed camshaft.
Yes. When time permits, I'm going to remove the valve cover and see if I can get a good look at the camshaft—with emphasis on cylinder #1's lobes. Is there anything that can be done to make the oil dripper more effective? It's my understanding that this is the weakness that causes the premature wear on these lobes.

Originally Posted by H.D. View Post
There may be no need to do the valves or the valve guides, even with 200,000 miles or more on the clock. What should be done though, especially if it has never been done before, is the valve stem seals. (See also what I said in post 100)
I hope you're right. My concern is that with burning a quart or so of oil every several hundred miles, the engine suffers carbon build up from burning tiny amounts of oil that have leaked through the stem seals. This is why I regularly add either of LiquidMoly or Seafoam or Lucas upper engine fuel treatment. I guess my question is: How do you determine that valves need replacement without dismantling the entire upper part of the engine? Seems a bit of a catch-22 in that if you're going to the trouble of replacing the camshaft and rocker arms, wouldn't you do a valve inspection then—instead of buttoning everything up to see if the replaced camshaft and rocker arms along with stem seals solves the problem?

Originally Posted by H.D. View Post
Might be failing lifters. In that case I suggest to replace them when you replace the valve stem seals. They‘re not very expensive either. If you don‘t buy them at the MB dealership, I recommend the ones made by “INA“.
So just what is a "failing lifter"? If they're hydraulic, I can understand that perhaps the mechanism is worn and needs replacing because there are oil and springs involved. If they're not hydraulic, then how does a lifter wear out? And if one replaces one lifter, shouldn't I replace all twelve?

Originally Posted by H.D. View Post
You too? …

Thanks for the compliment about my 300CE … my wife, who actually doesn’t care so much about cars, kept me from selling it about 10 years ago … she loves cruising around with it.

That picture of the engine bay, btw, also shows something that you usually don‘t see there (the grey plastic cap below the arrow. It‘s part of an on-board CIS-E test device … something those who plan to keep their CIS-E cars for the longer term might want to consider. This link leads to more details about it:
I'd love to own a fleet of 126s; I love these cars. Today a friend sent a pic of a 1991 420SEL for sale—with a mere 61,000 original miles on the clock, and I'd love to have it for the $14,500 they're asking. 300 SE is more nostalgic, and I love the color. I budget permits, I'm going to have her painted this year. And the M103 is more economical than the 4.2L V-8 of that era. Essentially, the shorty 300SE is an easier 126 to maintain even if it lacks a few of the bells and whistles. And the '91 I found is black—which, while beautiful, is a bit too "limousine-esque" for me; I'd feel too self-conscious driving it. Nevertheless, one of these days I'll have my 300SE's valve cover repainted and get the entire engine bay properly cleaned and detailed.
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