Haven't seen this one before

[maj75]

So what was the mechanism of failure?

It must have been installed correctly at some point, otherwise the engine would not have lasted 62K

What could have caused this seal to deform?

[Brad Roberts]

The seal has a metal band inside it for strength. I believe the seal was damaged prior to install and water caused the metal to corrode and eventually weaken.

I'll pull the seal apart today and post a pic.



B

[stephen wilson]

I just had a similar failure on my Chevy truck. The seal was supported by a hard plastic "cage", which cracked, letting the seal bulge into the coolant passage.