Cracks in aluminum sumps

[sgt_doofey]

I know that there are a great number of mechanics on here and would like to see if they have ever seen cracks form in aluminum sumps?
Our Peugeot 307 has had a crack repaired in it at the last service at a reasonable cost to us. The car is 3.75 years old and out of warranty, so I'll be chasing Peugeot Australia in regards to the reimbursement of the costs as I believe it's a manufacturing fault.
The dealer has said that the cracks are actually there in the sump due to the casting process.
Have the mechanics out there seen aluminum sumps crack, usually due to stress fractures in the aluminum?

[outback_ute]

It does happen, also gearbox cases. Often happens after the sump it hits something eg a concrete carpark chock. The location of the crack there at the drain plug would be an interesting coincidence... Having a pressed steel sump is not a bad thing in my view.

[Silver Ghia]

The casting does look a little rough especially in that radius (or is that a weld?), probably some porosity in it too.

But the plug when tightened would exert some stress in the boss area where its cracked, also someone leaning on the spanner would stress it further where its cracked.

[sgt_doofey]

Originally Posted by Silver Ghia

The casting does look a little rough especially in that radius (or is that a weld?)

Yep, that's the weld where it was fixed.

But the plug when tightened would exert some stress in the boss area where its cracked, also someone leaning on the spanner would stress it further where its cracked.

What if I say that the sump plug was replaced at the previous service due to it being damaged? What do you think happened in this instance?

[Silver Ghia]

So that line next to the weld bead is not actually a crack, just the edge of the weld? To me the boss doesnt seem thick enough, may crack again there next to the weld if they put too much pressure on it in the wrong direction.

It does sound suspicious regarding the damaged sump plug. Do you know what sort of damage and how it was damaged?

[sgt_doofey]

I was told it was stripped. That's all I know. It was replaced under warranty though.