Mentioned elsewhere that I've the bulkier radiator / twin fans from a TD fitted to my '89 1.9 GTI.   I've the expansion tank off at the moment and will likely be replacing it due to heavy corrosion around the metal inserts of the various inlets.   This is an internet image of what my existing tank looks like...     Is this the original type of tank for a 1989 GTI, or if there is a difference, was it too changed to a TD item at whatever time the radiator was exchanged?         As a side issue and because there's a couple of good write ups on the forum about the coolant level sensor (and the problems they can have) I took mine out and sure enough it was completely clogged up and wouldn't have been able to show a low reading .   The white circular float with the ring magnet in the images below was stuck half way up the central rod you see in the brown housing, it needs to be able to rise and fall with the coolant level to activate / deactivate the warning light.   Didn't take much to clean it all up and it now slides up and down freely, which I thought would be the fix.   Unfortunately the sensor still didn't work so took the top off and pulled out the gubbins you see with the pink blob on the end.   The photo was taken after I re-soldered the thin wire to the metal part holding the glass reed switch. It had corroded and parted company... the blob is resin I added after to make it stronger / watertight.   The cavity it sat in was full of a marzipan like material, presumably some sort of waterproofing, but it'd obviously not done its job.   After the insides were out I filled the empty cavity with acetate thinners, couple of washes cleared dissolved and washed out the old filler.   I used white grease to pack it when refitting, works perfectly now.   No doubt someone will show me where to get new sensors for a couple of quid, but apart from the satisfaction of doing it myself, I could only find one on-line and for over £90!   Hopefully save someone else having to fork out for a new sensor too.