Nissan Repair: Nissan serena 1.6 gx p reg, coolant system, radiator cap

Question
Hi I recently bought a Nissan serena and found that the head was cracked and so on replacing the head etc have found a nother problem surronding the coolant system. On completeing the rebuild we cleaned the coolant system out and then filled with coolant. Everything was fine for about a week and then on taking it on a longer run realised that there was a problem that being that it is filling the coolant bottle and on removing the radiator cap you can see that it is circulating but its a trickle, and the radiator looks like its only ever have full,because its kicked the rest into the top up tank.

Answer
Jamie,

Check the thermostat for blockage.  The cracked head means someone probably used a block sealant and the cooling system needs to be drained and flushed.  This includes removing the drains from the block to get all the stuff out of the water jackets that surround the cylinders.  This was probably not looked at since all the sealant falls to the bottom of the block and gets stuck there.  So, have the systme flushed and the thermostat replaced.  And, while they are at it take the radiator out and inspect for blockage too.  Again, the stuff will be mainly at the bottom like the engine block.  A mild flush agent along with multiple flushes should do the trick.