I only know a bit about the Gen 3 CRV engines. As far as I know they don't have coolant drains.
Are there any years or models that do? How stupid not to have block drains. A coolant change
leaves about a half a gallon behind.
After writing this I used a mirror and maybe there is a coolant drain in the block? Does anyone know for sure?

 

On B series blocks there's a coolant drain plug on the front of the block, and I think one on the back as well.
The one on the front should be right next to where the engine is stamped.

Unless you're talking about a K series engine in which case I have no idea.

 

Okay, I was looking at a few parts outfits online and the crappy parts photos show various plugs. Then I found a block heater that is available, that would need a threaded coolant hole located some place on the block.
Can't get under it to look yet.

 

Important note, if you plan on threading something in there -

The thread pitch is extremely uncommon. It is M28 x 1mm. Also, if that plug has never been removed in the ~30 years of that car's existence, you can be almost certain that there is a lot of corrosion in the threads. That coupled with the fact that it's a fine thread, high torque fitting means it's extremely easy to cross thread the port.

Go slow, use lots of lubricant, and clean the threads as best as you can before putting in another fitting. Caution should especially be used if the block heater fitting is aluminum/brass which is likely.

https://honda-tech.com/forums/forced.../#post52697228

 

Not wanting to put anything except the original plug back in. I just want to drain the bad coolant out of the system, and not have a half gallon of water left due to flushing. I used the block heater deal to research if there was a plug someplace on the block, that is all.

 

The block heater on a K series does not touch coolant. Just a blind threaded bung on the back of the block above the oil filter.

 

aren't the water pump and the thermostat hosing mounted below the water jacket on the front of the block? so changing the thermostat, or at least pulling it out should drain the block completely.

B-series and other CCW blocks can be almost fully drained by pulling a heater hose from the metal tube under the intake manifold.

 

Yup! Makes a fantastic mess too!

 

When I get the time will keep researching the drain issue. It will be pretty sad if the only way the cooling system can be totally drained is to remove the water pump, or better yet take out the whole engine and flip it upside down .

 

Is it not next to the oil filter? It is on Accord K24 blocks.

 

That's a blind theaded hole on every K series I have looked at. It's where the block heater would go. No communication to the coolant passage.

 

How brilliant of honda to not have a block coolant drain. I'm sure glad there were smart engineers back in the 1950's that knew how to do things. Its like everything they figured out has been forgotten.

 

It's an extra $0.25 to drill and tap a hole and another $0.45 for the o-ring and plug.

Over millions of units that's a lot of profit to be had.

 

Strange the picture calls it a drain plug?

 

If I ever have to do an overhaul on one of these engines, the first thing I do is machine a proper block drain plug, or two.

 

That’s funny because I just removed this drain plug on my Aunt’s 2005 2005 Honda CR-V and a bunch of coolant came out. There’s a plug with a 10mm Allen hole. It was really easy to get out from above with a 6” extension. I filled the radiator with distilled water and eventually it started draining again from the block drain. I let it all drain out from the radiator and the closed the radiator drain and filled with coolant until it started draining out the engine and then I put the plug back in.

 

You might want to check because mine was a drain plug. You need a 10mm allen socket. just take a photo with your phone if you are unsure