I've just had one of my mad thinking outside the box cunning plans.
Radweld or Kseal type sealant.
NOT for the whole cooling system. I never quite trust the stuff not to clog the system up with expensive consequences.
But what about just for the heater matrix? (basically just a little radiator. ) But crucially without the need to remove the matrix from the car.
Contrive a way to plumb in a self contained mini coolant circuit through the matrix by disconnecting heater pipes where they are accessible, perhaps under the bonnet. Include a pump to repeatedly circulate, the mix until it has sealed the matrix and maybe some method of keeping the liquid hot , if this is necessary to cure the sealant . Voila, a sealed matrix without having to risk clogging the main cooling system. You'd need to check for continued leaks for a while. A big and elaborate undertaking but so is removing the matrix.
I have never done it,and probably never would have. Except maybe on an older car than this . I dont know if it would work , and its entirely at your own risk.
