nissan serena checks?

Hi I recently purchased a Nissan Serena P reg and found the head was cracked so replaced head. Now finding that I am losing coolant from the system, it seems to be pushing it back up into the top up tank because every time I drain it down to the max level and on going a short disatnce I find that once the engine has cooled on taking the radiator cap of it very low and takes around half a pint to top it back up, and the level in the top up tank has risen can you please help why is it doing this?

Jamie
November 2008

the thermostat is sticking-you can confirm this if you can get at the thermostat housing you can probably remove the cover then take out the thermostat and replace the cover- mind the necesary large coolant leak this will cause- engine will now run without over heating but never really reaching full operating temperature- then fix it properly with a new thermosat and gasket- renewing coolant/antifreeze as necessary-

oldchapel
November 2008