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Anyone know the actual size of the bolt on the back of the engine block to drain the coolant. Thanks for your help.

 
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never heard of a bolt on the engine block to drain coolant. must be me but anyways what are you looking for what size wrench you need, or what size replacement bolt?

 
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Its right next to your oil filter.

 
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ohhhhh i see. so what measurement you lookin for? best bet would be to call honda or just keep trying a few diff. wrenches on it make sure you use the 12 point end of wrench not the open end or youll stip that sucka

 
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not a 12 point, a siz point is what is needed, but what is the damn size of the bolt.

 
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I'll give you a hint - it's metric.

Just figure it out - it looks like 12mm or maybe 14mm.

Seriously, just put a ratchet on it, you have four choices on these engines for the most part - 10mm, 12mm, 14mm, and 17mm. You can pretty tear apart your whole engine with just those sockets.

And dude, if you're intending to drain your coolant, there's a plug on the radiator that's much easier to get to. Unless that manual says to drain coolant like that, you should be using the radiator to drain, not that plug.

 
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the radiator drains the coolant from the radiator. The bolt on the back of the block drains the coolant from the engine block.

Funny thing is the washer for the bolt is 28MM.

 
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Maybe I'm just stupid, but why do you need to drain the coolant from the block?

 
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Well when changing the coolant it is good to have all new fluid in the system. Having the old fluid in the block will eventually mix with the new coolant and will become contaminated.

 
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yup

 
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I think its a 19. It may be a 17 too, can't remember off the top of my head.

 
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well whatever it is, I am taking my 12 volt impact wrench to it cause I know that thing has loctite on it and will be a bitch to get off.

 
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Whoa there tiger, that's probably not the best idea. Why don't you flush your entire system? Haynes/Helms repair manuals outline the process - you basically detatch a coolant hose and run water through the system until the water becomes clear. Then replace with 50/50 or your preference.

The bolt is just unnecessary and you're still left with contaminated particles and films of dirty coolant and such that draining alone won't clean. Oil changing garages usually do this with a handy pressurized system for like $10-$15.

 
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Exactly, 12 posts and no one mentioned this , I think i learned that in General Auto 101 lol.

 
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Well then I am guessing the best way to do this would be to drain the coolant from the radiator, then remove that bolt on the back of the block, to drain the rest of the coolant, then remove one of the hoses a run fresh water though the system untill it runs clear out the back of the block.

Whatever way, I dont want to leave any water sitting in the engine block. How does this sound?

 
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now is this with the engine running or not?

 
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not running i think... but it doesnt matter if you levae a lil water in the engine block its not gonna be enough to throw off the 50/50 balance when it mixes. and whatever you do never put more water than coolant

 
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Theres a point to having a coolant drain on the block, so why not use it if you don't want to take it to a shop?

 
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There might be a point to having that coolant drain bolt, but just like someone else said: flushing is the proper way to do it; that's what I learned in my auto shop classes. I've never heard of using a block coolant drain bolt to change coolant. As far as I know, that coolant drain bolt is more for draining coolant during an engine build or such, if necessary.

And don't worry about having just plain tap water in there for a few minutes - it takes time and heat for it to oxidize and rust. Adding the coolant or water wetter to the mix after you're finished prevents that from occuring anyway.

It's your call on pulling that plug out. I'd be hesitant to do it because I'd probably have trouble getting it back in and not leaking. Just another hassle. Plus, a hard to get to 17mm or 19mm bolt that you have to loosen/tighten from under the car? No fun

 
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well I just finished changing the coolant. Instead of pulling that bolt out, I went ahead and drained the radiator, filled it with a flush solution and water, ran the engine for 10 min, drained it again, filled with water and ran it, then drained it and filled it with new coolant.

We never really discussed this **** at school, but I think I did ok.

 
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