K.O.R.C has several high pressure jet washers.
Maybe something akin to this,would help to clear the radiator before the mud sets solid.Better than having a cooked head..
http://www.nomad-direct.co.uk/index.php/Products/Nomad-18-V-Cordless/Nomad-18-V-Orange-with-1-Li-ion-battery/p_50.html