some advice pls :(

[dieselboy]

fit a hose pipe to the small hose on the bulk head
blow it throw with fresh water it will spit out the all the crap inclueding the aire block leave the water cap off while doing it
i have had the same problem for ages now
its all gone since i fitted a new rad
but i had 4 years out of the last one witch iwas 15 years old
flushing the system cured mine for a while

may work for you its worth flushing it all out tho init

nice idea, ill see how it goes. ive always put in load of antifreze so i had hoped there isnt any crud in there, but you never know