Heating Matrix Blown!

My beloved Mk1 Golf Cabriolet 1989 has blown what we suspect is the heating matrix. My uneventful drive from work was interrupted by a horrid smell of plastic burning and very quickly followed by a smoke in the car. Once I pulled over and popped the bonnet a steady stream of smoke was coming from the vents of the matrix.

Has anyone experienced this, have advice or a technical drawing for changing the heating matrix?

Thank you for any advice.
 

Check out this thread: http://vwgolfmk1.org.uk/forum/index.php?page=topicview&id=big-block-injection_2%2Fleaking-heater-matrix_2

it is a bit fiddly, but not too bad.

While Heating Matrix's (we call them Heater Cores)
Do leak, you said burning plastic which would tell me that the Motor is more suspect than the core.

A/C equipped cores remove differently, and non-a/c
But I would ask if the Radiator Expansion jug is low before I tried to do a heater core.

They make a pressure tester cap that you place on the expansion jug then pressurize it to like 14-18psi, and you will find a leak rather quickly without having to run your engine.

For a/c Equipped there is a how to that you can use but after wards you have a ugly seam where you cut it out.
I have the fix for that to make it more OEM.  As in the A/C equipped you have to take the dash out to do it correctly.

http://www.driversfound.com/scirocco/techtips/body/heatercore/

My creative use of a old tool tray plastic and 3 trim screws to make the cut "invisible?"ok, slightly less obvious.