S40: - T4 Cylinder Walls

Asosis · Dec 31st, 2019, 10:58

Hello

Does anyone know what has caused the black ring at the top of each cylinder and/or is it normal? And are the cylinder walls looking fine?

canis · Dec 31st, 2019, 14:59

Not an expert, but that's just where the pistons reach the limit of their travel. Don't worry about it.

And don't try to clean it off either! Any abrasives or cleaning products will inevitably get into the bores, into that tiny crack between the cylinder and the piston, and do enormous damage when the engine is cranked and forevermore thereafter.

The diagnoal marks are probably from when the bores were initially milled. the fact they still show must be testament to good oil pressure, I'd expect.

Dippydog · Dec 31st, 2019, 17:30

As Canis says I wouldn't worry,the diagonal marks look to me to be the honing marks[last process in cylinder boring]and the fact they're still present is a good sign.

magnuz · Dec 31st, 2019, 17:31

That is normal, as the actual rings of the piston do not go all the way to the top of the cylinder. In some cases, you may also be able to feel a slight "wear ridge" which is not really a problem, unless you are fitting new rings.
The cylinder walls look to be really good, .. as you can still see the "cross hatching".. This would not be as visible on worn bores.

Asosis · Jan 4th, 2020, 17:31

Quote:

Originally Posted by magnuz

That is normal, as the actual rings of the piston do not go all the way to the top of the cylinder. In some cases, you may also be able to feel a slight "wear ridge" which is not really a problem, unless you are fitting new rings.
The cylinder walls look to be really good, .. as you can still see the "cross hatching".. This would not be as visible on worn bores.

Exactly what I thought mate, engine has done 200.000 kms, and it's looking decent..
I'm still gonna hone it very slightly with a drill and honing tool, as I'm fitting new rings..

It's been running 1.5 bar for almost 10 years, and to be fair has had a rough life.. But regular oil changes and quality oil has kept it running.

Dec 31st, 2019, 14:59	#2
canis Non Fragile Last Online: Oct 13th, 2023 05:46 Join Date: Apr 2010 Location: Chadderton, Oldham	Not an expert, but that's just where the pistons reach the limit of their travel. Don't worry about it. And don't try to clean it off either! Any abrasives or cleaning products will inevitably get into the bores, into that tiny crack between the cylinder and the piston, and do enormous damage when the engine is cranked and forevermore thereafter. The diagnoal marks are probably from when the bores were initially milled. the fact they still show must be testament to good oil pressure, I'd expect.

Dec 31st, 2019, 17:30	#3
Dippydog Premier Member Last Online: Yesterday 19:11 Join Date: Jun 2016 Location: S****horpe	As Canis says I wouldn't worry,the diagonal marks look to me to be the honing marks[last process in cylinder boring]and the fact they're still present is a good sign.

Dec 31st, 2019, 17:31	#4
magnuz Ancient Last Online: Apr 15th, 2024 17:03 Join Date: May 2012 Location: chesterfield	That is normal, as the actual rings of the piston do not go all the way to the top of the cylinder. In some cases, you may also be able to feel a slight "wear ridge" which is not really a problem, unless you are fitting new rings. The cylinder walls look to be really good, .. as you can still see the "cross hatching".. This would not be as visible on worn bores.

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