Hi,
thanks guys. I have an old Mercedes thermostat which is made the same way. Housing and insert. So i had the opportunity to test if i could change the insert without rocket science tools made from depleted uranium.
Well, first i searched something that fits over the cap of the thermostat, just to press the two flaps down that hold the insert. Found a plastic cap in the bathroom and it was pretty easy to get the insert out.
But how to get it in? The plastic cap didn't work. Too flexible, couldn't generate enough pressure to fit it in. Tested the 2 screwdriver method with two bigger flat blade ones. Nope, that didn't work. Went to the cellar to look for a metal tube that might fit – unsuccessful. Also no other tools in that big toolbox that might solve the problem.
Decided not to drive to the hardware store, because in the end a complete Wahler thermostat incl. seal is only 11 Euros more than an insert without seal. Doesn't make sense from a ecological point of view, but if i add time for fabricating the tool myself and driving and buying stuff at the hardware store it seems to be cheaper than to buy a complete unit. So i ordered the complete one.
Conclusion: you can change the insert but you need to have a special tool made from metal.
Thanks & regards
Markus