Are you sure there isn't a large air bubble inside the block that is fragmenting & causing the stream?
The only other approach I can suggest is (if you've got a sub pump) - submerge the lot in a bath or big sink, keep it sealed though. With everthing under water there should be no way air can get into the system. Then try slowly lifting different parts (interconnecting pipes, pump, block, rad, etc) out of the water & see if the air returns. This kind of the reverse of checking for a bike tyre puncture.
Hope this helps.
|