Oil leak behind crankshaft pulley

We have a small leak behind the crankshaft pulley. To fix this do i simply take off the rear tinware, remove the pulley then remove and replace the seal, dropping the oil out and getting the seal as level as possible when i replace it?

Is this a common fault or is it a warning for something more serious?
Can this be done with the engine in situ?
What is the correct part to order as i cannot find a diagram/correct name anywhere?

Thanks in advance

 

When you say rear do you mean the nearest when you're looking at the engine?

Type 4 engine yes?

 

My mistake again.

Type 1 engine, 1600 Twin Port.

The rear tinware i am meaning the one nearest to the engine door/nearest the rear of the van, i need to take that off, i believe, to take the bottom pulley off.

There was some oil spray and some oil on the back (other side when looking at it) of the bottom pulley.

 

On a type 1, there isn't a seal behind the pulley, just an oil thrower inside the crankcase.

Are you sure this is where the leak is coming from? Possibilities: aftermarket crank pulley, or excessive crankcase pressure.

 

Could be oil leaking from the pushrod tubes and running down the tinware