What is that gunk?

[Smiffo]

So I have been working through a few `weeping coolant` issues lately.
Nothing major but persistent issues.

Now, both hoses that were leaking had a `crust` or debris between the hose and the respective outlet port they fix to.

At first I thought that was the issue - an un smooth face that let liquid through - but now I am wondering what it was?
Is it the dried out coolant that was present, or was it some sort of sealing compound put on by a previous owner?
Which leads me to ask; should I be using a sealing compound where the hose attaches?

I wish I had taken a few pics to show exactly what I mean, but this thought only occurred to me now.

Any immediate thoughts anyone?

[bigherb]

Yes usually it is dried glycol or/and oxidised metal if it was on a alloy part.

[Smiffo]

Yes usually it is dried glycol or/and oxidised metal if it was on a alloy part.

Thanks Big Herb.

Both places were on inlet manifold and RH head to coolant tower ( so yes, it was where hose meets metal. )
I lightly sanded it all off and gave it a good clean up - seems to be OK - I'm going to take a little run later and make sure it's all water tight now