Another block flush question - when to do it

[togntime1]

Drained the block from the drain on driver side. Pried out some gunk from the drain hole then it flowed great. Ran some water through and it comes out clean and free. Been reading about the clogged water jacket near end of block between 5th and 6th cylinder. If there was a restriction would the block drain freely and clear?

 

[1969FJ]

Drained the block from the drain on driver side. Pried out some gunk from the drain hole then it flowed great. Ran some water through and it comes out clean and free. Been reading about the clogged water jacket near end of block between 5th and 6th cylinder. If there was a restriction would the block drain freely and clear?

Sounds ok to me. Usually, the crud builds up and restricts flow through the narrow passages. Sounds like you got it right.

 

[SteveH]

You've done all you can do without pulling the head. I would leave well enough alone, and if the coolant turns up rusty in the future, then flush again. The drain plug often plugs with gunk and requires that you push a screwdriver through the gunk plug to get it to run free. I bought a '77 engine that sat in a shed for 12 years, and suffered from some rust inside the block. This rusty gunk eventually plugged the radiator, but after flushing and a new radiator, it has been fine for the past 25 years.

 

[73FJ40]

@togntime1


My engine sat for 20 years. I had to recore the radiator, but I didn't want to plug it up with the crap that had to be in the block to ruin the new core.

I installed one of these, and it worked pretty well!