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2005 SLK55 AMG /2005 SLK350
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Discussion Starter · #41 ·
I'll do that. The machine shop was closed yesterday for a family emergency, so I will have some time today and tomorrow for further inspection. I did look over the head with a "straightedge", but it was not long enough to span the entire length, plus I have my doubts about its straightness. I may buy a longer and trustier one later today.

Just thinking out loud, what are your odds for a cracked block? Have you ever seen such?

If I am extremely careful to keep all the slack out of the chain, would it be advisable to rotate the crankshaft 180 degrees (and exactly back) to inspect the # 1 cylinder further?
 

**Premium Member '02 R170 SLK V8 5.0 & '00 SLK320
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Just keep the Chain tight ;)

I don't have enough dealings with the M111 to advise about possible Head or Block issues ;)

Something is catastrophically up with Cylinders 1 & 2 to have such low figures of 20 psi and 0 psi Compression and the lack of apparent damage to Head Gasket suggests that is not the causal part :cry:

IMHO it'd have to be bloody great big and easily visible crack to be that low on compression ;)

Do you have relevant history, i.e did the PO buy it after it had stood for many years and get it running (badly) just prior to sale ?

What do Camshaft Lobes look like ?

Any evidence it was driven through a flood?

More info needed ;)

Another thing to try is to turn engine so 1 & 4 are down the bore by 10 mm, and fill bores with very light oil, like Diesel etc to say 5mm below face see how quick that oil disappears, then do the same for cylinders 2 & 3 ;)
 
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**Premium Member '02 R170 SLK V8 5.0 & '00 SLK320
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/\ /\ /\ Continued from my post above ......................

Look at this picture of yours and clarify please ....

clickable:-



Is that marking / damage on the edges of cylindesr 2 (and to a lesser extent 3) Cylinder Walls ? From here it looks awful but may jus be dirt from disassembly ;)

Also is it a Photo Angle thing or is Cylinder 1 Piston sitting lower in it's Bore than Piston 4 ?
 
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**Premium Member '02 R170 SLK V8 5.0 & '00 SLK320
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I just did some digging, Post # 1 here :-


"I blew the head gasket this Sunday in Atlanta, Georgia. There was a coolant leak, and I was taking it to the mechanic when it blew."

Sorry to say but that suggests to me it got very hot, he "assumed" he blew the Head Gasket, which in the pics does not look that bad, so personally I would want to get the Bores and Pistons checked out very thoroughly before spending a bunch of coin on this Engine. It may be more cost effective to just slap in a good running used Engine ;)

Is it possible to remove Sump and Pistons / Con-Rods without Engine removal ?

Bores need measuring as do Pistons and Rings if you don't find warped Head / Block Faces ;)
 

*Premium Member
2005 SLK55 AMG /2005 SLK350
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Discussion Starter · #45 ·
I'm in puzzled agreement with you - reduced compression is not the same as zero compression. That is spray cleaner running down the cylinder walls from where I cleaned up the grime near the surfaces - the bores are pretty smooth. I'll clean things up thoroughly with a brass wire wheel, make measurements, and post more thorough photos shortly. The piston pairs are both at the same depth.

Yes it's been overheated at least once, and I knew that going in. The PO did not drive it long in that state though.
 

**Premium Member '02 R170 SLK V8 5.0 & '00 SLK320
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Fingers are crossed for you (y)

If not, I can tell you exactly how and what is required to fit a V8 :D

Do you have a local engine shop near you who may have a Bore Mic, if nothing else surfaces on close inspections you'd be looking for ovality of the Bores ;)
 
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Well, first do Dave recommendation in post #40 of using brake cleaner or some other liquid in the intake and exhaust valves to see if it's air tight or leaking.

Mercedes usually -- usually -- just wrap the head when overheated to the moon, and that's if they don't lock up in the first place. Not that common, given that the average Mercedes has onety one billion nanny lights, beeps and outright buzzing when it overheats..... But 馃挬 happens.

Check the head before you start grabbing speciality tools to measure the bores, rods or whatcrap.

Depending on results, like he said, cheaper to chuck in used engine than rebuilding it.

With compression results that low, I was expecting mangled valves. The fact that valves look good is concerning.

How is the rocker arms on the head? Any broken ones?
 

*Premium Member
2005 SLK55 AMG /2005 SLK350
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Discussion Starter · #50 ·
Cylinder 1 lost all the mineral spirits within a minute or two, the others are still holding after 25 mins. I don't really trust my straightedge but it shows . 005 in gap between 2 and 3.

The closeups of the block show some bad pitting, these may be the problem area. The photos are after cleaning with my surface prep tool.
 

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How is the crosshatching on the cylinder walls? Can you still see them on all 4 cylinders? Rotate the engine and see.

Those pitting you're referring to is inside the coolant passage, I'm not worried about that.
 

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That pitting you're referring to isn't bad, if you look at the cylinder head, the orifice that is on the opposite doesn't actually press down on the ridges, so coolant can just lift the cylinder head and pass through port to port, but not out. I would say it's fine....ish. Maybe Dave can input.

Is there any area on the cylinder walls where the crosshatching disappears? Or it's smooth cross hatching all across?

Mineral oil drain test is not exactly a good test. It's a good test to supplement other tests, but on its own it's a misleading one. Piston rings can easily rotate in a way that the gaps aren't too far from each other and you can be misled by that.

The cylinder 1 valves are definitely leaking though, but I'm slightly puzzled by the 0 compression in #2.
 

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Discussion Starter · #59 ·
After an hour, the mineral spirits was completely drained past the valves in 1 and 2, 3 and 4 are both holding still, but down about half way (perhaps due to evaporation).

I've seen enough to proceed with a valve job and skimming the head.

Thanks for your gracious help and insights!
 

**Premium Member '02 R170 SLK V8 5.0 & '00 SLK320
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so coolant can just lift the cylinder head GASKET and pass through port to port, but not out. I would say it's fine....ish. Maybe Dave can input.
I agree that is not a concern.

I still wanna know why number 2 has no compression at all, number 1 yeah fine, valve job ;)

I've only seen one side of the Head Gasket between 1 & 2, any chance of a picture of both sides of that plz ?

Check that block face for warped too, and while the Head Shop have the Head ask them to pressure test it ;)

The last thing I wanna see is when it's all back together is "It started up fine BUT ....................... " :eek:
 
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