Outer Limits 4x4 Board

gday,
i have just purchased an FJ40 running a Isuzu 4BD1 engine,im not sure if the radiator is a stock one or as been upgraded but it is a fairly big one,it is losing a small amount of water and there are no visible leaks
after taking it for a drive you can hear a hissing soud coming out of the radiator cap,and it looks like water has been squirting out of there in the past,im thinking that the radiator cap may not be suitable but im just after any other advice
cheers

radiator cap is either fubar or its not the correct poressur rating

go to ya local parts shop and tell em what ya need

would there be another problem causing it to hiss?

Just replace the cap at a proper rad shop, and check for any cracks around where the cap goes on..