Changing Engine Coolant

[Jules]

When changing engine coolant for Honda vehicles, is it recommended to remove the drain bolt on the cylinder block, to achieve full drain on the system?

Topic

[Lorrin Barth]

If you can get to it and get it out the answer is yes. If you do remove it, wrap in in teflon tape before inserting. These bolts like to rust weld in place.

[Ingvar]

Teflon tape is not really necessary, as washer seals everything quite well. But cheat bar or breaker bar is highly advised, those are immensely high torqued from the factory.
Book will tell you to put new washer on, so use copper one. But for the sake of sanity, I simply flip it 180 degrees and reuse same washer. DO NOT overtorque though, or you’ll bust the washer and THEN it sure will leak.
And should you have V6, you likely have 2 block drains.

[Jules]

I’ve done this a couple of times. But the reason why I asked is that I’m having doubts, because when I asked some friends of mine from Honda (the Company I used to work before) is that the bolt itself is highly tightened and it is possible that it could result a lost thread or maybe when things gone worse I could even damage the block when it cracks and they even told me that they have to heat the bolt first before removing it.

[Erin]

In cases like this –

I would say drain as much coolant as you can, run the engine for a few seconds to see if it can pump more coolant out, close the system off, refill with anti-freeze/water mix, run the car for a while, drain again, then refill with antifreeze/water mix.
That will get most of the old coolant out. Yeah it wastes coolant and costs a bit more since you will need more than usual.

One thing about this – when you do the first draining, measure how much comes out (maybe fill up a gallon jug a few times to measure this) and compare that with the cooling system capacity. Most of it might end up draining. I am guessing you will probably get it at least 75% empty just by pulling the lower radiator hose or if there is a drain plug.

If those engine block plugs have a good chance of stripping threads on the way out or completely breaking, it just isn’t worth the risk of trying to remove them.

[Lorrin Barth]

I’m having a hard time believing that the Honda Company would have reason to highly tighten a drain bolt. More likely it corrodes into place after a few years. My experience is that if you have had to drain bolt out when the vehicle was new and protected the threads, then you will be able to continue using the drain. Otherwise, no.

[Author]

Replies