Forged Piston Skirt Cracked

Calum122

Member +
So found out why my engine started knocking...



Question is, why did the piston skirt go. I wasn't driving that hard and it's not a brand new build. Engines been around for a while. So I would almost rule out poor engine assembly.
 

Jay

Admin
Ouch..

Any better pics of the top, the sides and other pistons for comparison?

Just in case there's signs of detonation, heat or something else lurking about.
 

SKINY

Lifer
Well maintained engines can pop as easy as the poorly maintained ones unfortunately buddy :(
My A4 110K with full Audi history shit the bed this morning, spark plug No1 put up a valiant fight but lost to the rampaging piston/piston parts lol, rod seized again the block it's away to junkers now :)
 

Calum122

Member +
Sad times. I have got another car I don't know if I told you guys, like the starlet I have had it a month and already taken it off the road for repairs. I should not be allowed to touch cars. In five years of owning the starlet I done less than 2k miles, yet replaced every single bush, powdercoated ever part underneath. Welded up both sills and both sides of the floor. Countless other mods. But never drove the fecker hahaha. This new car, much of the same.

. I just moved house and I have not had any Internet which is why I have not been on.





 

Jay

Admin
It might just be the resolution but there looks to be a bit of wear on the skirts of each piston, is there any corresponding wear on the bores?
 

SKINY

Lifer
Actually couldn't give a shit about it bud, it had been fucking about a while and gave no codes or clues, Drank oil for fun too.
Something else planned tho :)
 

SKINY

Lifer
Yea its going for welding soon then mot, all the bits on and setup then see what happens, really in 2 mins tho as the price is about to rocket on them but I've another itch or 2 left unscratched need a wee visit again
 

Skalabala

Member +
To be honest that looks like manufacturer problem :(
Other thing that comes to mind is the car was beat on when cold. The piston grows way faster than the sleeve does.
How cold is it where you stay? Frozen block?
 

Calum122

Member +
No, it was a shorts and T-Shirt day. And I never drive the car cold. I warmed it up on the drive till the idle dropped.

Then drove it for a mile. Then gave it some beans, but here is the clincher. Whilst I was driving spiritedly, I wasn't revving it hard or under load, but cornering Gs were up.

That went on for about half a mile. Then got to a Cross road and nailed it after changing into second. Don't like to ramp 1st. Then let off the throttle. Then about 5 seconds after the piston gave up.

I thought I starved the engine of oil going arojnd the twisties with low rpm. Wasn't expecting this to be fair.
 

GP82

Member +
Oh no :( You can have a look at the spark plug in that cylinder to see if it went lean, should be like a tan brown in colour. Spark plug tip will look chalky white if that cylinder was not receiving the correct amount of fuel. You will have to look at all the evidence as to what has happen. This has a tendency to happen when there is heat build up.
 

Calum122

Member +
Fueling was spot on. The engine is bone stock other than the forged internals. HKS actuator and HKS exhaust.

The bore was perfect. I say was, I scored the bore upon dismantling. Don't ask.

Basically, I am at a bit of a loss as to why it failed
 

Jay

Admin
Are the skirts on the other pistons showing any signs of wear or damage?

If there is, is the wear only on one side?

Looks like either piston slap or a lack of lubrication has caused the issue.
 

Calum122

Member +
Are the skirts on the other pistons showing any signs of wear or damage?

If there is, is the wear only on one side?

Looks like either piston slap or a lack of lubrication has caused the issue.
So it had a savage oil leak and it was lower rpm whilst taking savage bends.

I thought it was oil starvation.

Piston slap is possible, but I am confident that the engine was warm before hand.
 

Skalabala

Member +
This will not be oil starvation. The conrod has an oil sprayer. There will be severe bearing damage before you brake a forged piston like that due to oil starvation.
If there is ample amounts of piston material on the sleeve then yes. If this was caused due to piston slap then the slap must be severe.
How does the missing skirt look? Any sines of oil/heat problem?
 

Calum122

Member +
This will not be oil starvation. The conrod has an oil sprayer. There will be severe bearing damage before you brake a forged piston like that due to oil starvation.
If there is ample amounts of piston material on the sleeve then yes. If this was caused due to piston slap then the slap must be severe.
How does the missing skirt look? Any sines of oil/heat problem?
No the skirt piston is completely mangled.

It's amazing the engine still ran and got me home. I am sad to see this happened. I kinda hoped it was something I had done. But it looks as though it simply gave way!
 

SWJ

Member
WOW that is pretty messed up! I've not seen anything like that before?? A thought it would not hurt to contact the piston manufacture and get there assessment. If it is a failure on there part, Im sure they would want to know or perhaps they could give a better idea of what went wrong??
 
  • Like
Reactions: Jay

Calum122

Member +
WOW that is pretty messed up! I've not seen anything like that before?? A thought it would not hurt to contact the piston manufacture and get there assessment. If it is a failure on there part, Im sure they would want to know or perhaps they could give a better idea of what went wrong??
That is part and part of the issue. I didn't build the engine and don't know what parts were used. Could have been some cheap chinesium components for all I know.
 
Top