Engine block drain plug (coolant)

Ahhhh, I am trying to drain my coolant so I can replace my thermostat and I cant find the engine block drain plug. The only clue my Haynes manual gives me is that it is in the front of the engine block. Can anyone help?

I hope I'm not mistaken but I dont think there's a coolant plug on the motor itself let alone the block...try removing both hoses and drain it that way...I'll research further and let you know, in case I missed something.

look under the radiator ,,,it should be by the bottom corner

Yeah...thats the drain plug for the radiator...

On the bottom of the radiator on the passenger side theres a petcock that drains it, like how the guys said.

there is no engine block drain plug.... the only drain plug is on the radiator.....which IS the correct plug to pull. Most all the fluid will drain out. Then just unscrew the housing of the thermostat and replace it.

This Haynes manual is horrible: "after the coolant stops flowing out of the radiator, move the container under the engine block drain plug on the front side of the engine. Loosen the plug and allow for the coolant in the block to drain." Anyways.....I got my thermostat in....waiting for the RTV sealant to cure a little then Im gonna start it up and pray the coolant starts flowing....thanks for the help!

And I found out that there is an coolant drain bolt on the front of the engine block about half way up and behind the exhaust manifold. The only problem is that in order to get to it, it looks like one would have to remove the exhaust manifold and possibly the radiator.

Hey dudes...there is a drain plug..it is a pretty BIG bolt (17-19mm) and it is EASY to see on my ZC with the header off and it sitting on an engine stand. It is toward the tranny side, under the bottom of cylinder #1. It is prolly pretty hard to get to with all that stuff on it in the car. :(

Originally posted by spongerlbc
And I found out that there is an coolant drain bolt on the front of the engine block about half way up and behind the exhaust manifold. The only problem is that in order to get to it, it looks like one would have to remove the exhaust manifold and possibly the radiator.

That is a freeze plug.

Say your coolant or lack of, freezes in your block. Rather than cracking your block, it will pop those plugs out. It is easier (still hard) to put in a new plug, than putting ina new motor.

Originally posted by kris


That is a freeze plug.

Say your coolant or lack of, freezes in your block. Rather than cracking your block, it will pop those plugs out. It is easier (still hard) to put in a new plug, than putting ina new motor.


oops, I was describing the little round, concave looking plug on the block.

So what engine are we talking about?

My D15B (and the D15B2 before it) has a coolant drain on the block, on the front side, between cylinders 3&4. BIG bolt, 19mm bolt head with a very fine thread for a bolt that size (looks like a really big oil pan drain bolt).

And yes, I've used it to drain the block, it is a BIG hole, water comes out in a hurry. As it is a steel bolt in an aluminum block, I use a little anti-seize compound when putting it back in.

It is easy to get at, as long as the stock air intake on the radiator is removed. I don't know if it it gets covered by aftermarket exhaust manifolds, but the stock manifold doesn't block access at all.

And while you are at it, invest in a real Honda shop manual. I got mine from http://www.helminc.com. I have the same low opinion of the Haynes manual as others here.

J