I'm doing a job on a mk6 fiesta and there is a hole directly in the centre of piston number 4.

There is no signs of the valves hitting the piston nor is there any signs of the electrode on the spark plug breaking off and hitting the piston.

The spark plug in cylinder 4 however didnt look like it had ever been changed.

Has anybody else had a similar problem and also does anybody know what could have caused this as i am baffled to say the least

Thanks in advance

Mikey

 

is it a hole caused by Debris, or has it melted through det etc?

 

Tbh it looks like debris, that has hit the piston n then just instantly melted as there is a light coloured silver dots all over the piston

 

might be easier if you post pics of the head and piston

 

i'll try an get pics tomorrow, the head is totally undamaged though, which is why im a little confused on what has caused this.

 

I take it you know nothing about tuning, and this is the first engine you have ever taken apart ?


Clearly its been running lean/too much timing/too much boost....or any combination of those.

As your description shouts detonation and lean mixtures which have melted a hole in the piston.

 

sounds like detonation to me

 

dodgy injector?

 

No mate i'm 16 and learning but this isn't the first engine i've taken apart


This is exactly what the piston looks like

 

That is the piston, or it looks like that ?


Cleaning the piston before assessing damage isnt always the best idea.

Either way, the only thing thats going to hole a piston, is lean mixtures and/or detonation.

What are the skirts/ring lands like ?

 

thats what it looks like mate, havent had a chance to give it a proper look it was strip this job and move onto to the next, hopefully will get the piston out tommorow and look into it further.