because of the cars last owner leaving the car sitting with tapwater in the engine for over a year, it has developed corrosion in the block. I gave it a big flush originally , but everytime i fill it up and drain it out poo brown water comes out. I am hoping that the problem is not terminal as all the work I have done painting the enginebay will be in vain. I have heard you can put caustic acid in the engine for a little while, but I am worried about the hoses and gaskets. Is there a way to flush the block and remove all of the rust and scale? oh and I just found out that the A14/15s have a different thermostat from the 10/12s. and all along I had been buying normal A12 ones from repco.. sometimes buying genuine nissan helps. though 20 bucks is a fair whack for just a thermo!