1980 f100 300 i-6

trying to flush/fill coolant system.

shop manual for engine says the drain plug is in the "rear on the left"

uh-huh...

anyway, i can only find the oil drain plug underneath.
can someone point me in the right direction?

 

I think it is a threaded plug that takes a 3/8 inch allen wrench. I can't remember exactly where, I recall there was something on the side of an old I6 I was playing around with. I stuck an allen wrench into the plug and broke the wrench trying to get it out. Do not quote me, I'm not sure!! If you find it, realize that it may be super-seized, and your tools may break and knuckles will bleed.

 

no biggy.

instead i just pulled the bottom radiator hose off, pulled the return coolant line from the heater core and flushed it in reverse with a water hose.

I appreciate it.

 

you are doing what I do...there may be a little bit of tap water left in the block after the flush, and this isn't good, but not a serious problem. You should have used distilled water to dilute the antifreeze to a 50/50 solution...right?

 

Most OEM radiators had a "Stop ****" on the drivers side at the bottom facing the engine. Later radiarors and aftermarkets have a small plastic screw in plug that does the same. However I did see an aftermarket that had no drain plug/stop **** and no place to install any.

 

I have a 1948 F-6, and the radiator (replacement) as a small drain plug on the bottom of it, but that can't be what's in the engine? I have the 226 flat 6 cyl, where's the engine drain plug?

 

In regards to that how would you get rid of said water? I'd like to flush my coolant as well, perhaps it would be better to use the machine I have here at work to do a rad flush?

 

The idea though, with the block drains is to provide alternate path for accumulated rust and scale to be flushed out. Oftentimes they are all blocked and need persuasion to get flowing with an ice pick. Probably worth doing if performing a flush.

 

There is a block drain plug just about even with the top of the starter and about between #5 and #6 cylinders.