Any info I had seen on the forums mentioned having to remove the entire dash to remove the matrix, so had left it for the last 2 years. Whilst perusing the service notes I could see this wasn’t the case. ( I believe it is, however, the method needed for pre 86 MY cars). So a few photos and description below.
Worthy of note is there is a difference between the sound insulation between the SA and other models, there being more insulation in this area on the SA. So for the SA you will have to cut through the rubber sound insulation.
It’s also a little bit more of a PITA if the car has a/c as the pipes get in the way a little.. so if you have a non SA, non a/c car these are the easiest, although not difficult on the others.
If you can, do this with the rear of the car higher, that way you don’t need to drain the cooling system and will loose very little coolant.
To start you will need to remove the 2 hoses attached to the pipes protruding from the centre of the bulkhead that are part of the heater matrix. Then remove the 2 grommets around the pipes. Also remove the vacuum hose that comes off the back of the inlet manifold to the servo and rotate the fitting to point downwards to give clearance for the final stage of removal ( see last photo).
Drill out the 4 rivets marked in the photo below. For a/c cars you may need to also drill out the rivet holding the P clips for the pipes to the fresh air plenum chamber. I used a flexible shaft on a Dremel to do this.
The plastic cover is fairly thin so once rivets removed carefully ease it away to break the bond with the silicone sealant which will still be holding it.
This is then what you will see on an SA (for non SA - see later photo of red car). Some black foam that will crumble as soon as you look at it. You will need to remove this. Then behind this is the thick rubber sound insulation - you will need to cut around the edge of the hole to remove the section that is in front of the matrix.
Black rubber behind foam.
Rubber section cut away to reveal the heater matrix.
On a non SA once the cover is removed you will see the matrix straight away. Undo the screw and rotate the catch 180 degrees.
Make sure your heater is set to hot so it doesn’t catch on the flap when trying to remove. Then simply slide it forwards and out.
And as they say - replacement is just the opposite of removal. I used a Lazer swivel headed pop riveter to refit the cover and silicone to reseal.
Bleeding the coolant system works best if you can raise the front end of the car.