A customer at my friends shop had a old Toyota pickup 4x4 with that engine--his radiator leaked and he kept adding water instead of anti-freeze and it eventually got weak enough to freeze one frigid day a few winters ago,one freeze plug started gushing so he had my friend replace it,then he discovered the block had an external crack that dripped!..
It ddn't steam out the tail pipe or turn the oil milky,so he told the guy it'll need an engine,but he might be able to limp it along awhile by using some sealer...
The customer bought that "Blue Devil" sealer and used it according to the directions and the leak stopped after a few hours of running--my friend freaked out when he heard he used that stuff--he had tried it before and had bad luck,the stuff hardens like portland cement and clogs up things and in his attempts it didn't fully seal the leaks up..
But this time it did work,the guy drove that truck 3 more years and several thousand miles until a few months ago--the frame was so rotted the truck practically busted in two right behind the cab..his engine had well over 200,000 on it too...
Here its hard to find any Toyota parts,most are still on the road!--only ones in salvage yards are crash victims usually,and private sellers seem to think they are made of gold as far as prices go..
