Coolant Flushing Question

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I'm preparing to flush the cooling system and replace the thermostat on my 2005. I've read up on the procedure, and feel comfortable with it; but I am curious as to whether I can minimize the mess by first draining the coolant via the drain bolts in the block (with radiator cap removed of course), instead of removing the water pump inlet hose first. I'm assuming that either an air lock or the cooling system design prevents the majority of the coolant from draining from the drain bolts, otherwise someone would have mentioned it before. But, if these factors don't hinder coolant drainage, it makes sense to me to drain from the block first, so that when the hoses are removed there is less spillage.

Any comments?
 

Mellow

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I've never done it.. but, that is what I would do, remove as much via drain holes before moving forward.
 

nm6r

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...it makes sense to me to drain from the block first, so that when the hoses are removed there is less spillage.

Any comments?

Honda's brilliant design engineers made it foolproof to ensure spillage. Specifically from the drain bolt. The same engineer that was responsible for the helmet locks and tank prop must have located the drain bolt. IIRC, it is right behind a header tube. Not only is it difficult to remove and replace, it will unload right into the obstruction.

For as good as the ST is, the typical Japanese engineering still shows up.

Ray
 

Blrfl

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You can minimize the amount of spewage from the lower radiator hose by holding a large funnel over the joint as you pull it off.

--Mark
 

Byron

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You can also minimize the spill by not pulling the hose completely off to slow down the drainage. I spread old news papers under the drain pan to contain the mess.
 

NoBull

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Remove the hose just enough to get fluid flowing and let it drain. However mine still belched later and spit out a bit more. The drain bolt will make more of a mess, no real good way to catch everythingthat comes out that way...
 

BakerBoy

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Yup, it just is messy. Even after I drained everything as much as possible via the main hose, it was still messy when I then removed the block drain bolts. I had visions of a cleaner operation when I did mine...it just doesn't seem possible. If it is any help, here's my writeup.
-John
 

nm6r

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No problems with trapped air but there is a procedure in the service manual.

Ray
 

Scooter

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You can also minimize the spill by not pulling the hose completely off to slow down the drainage. I spread old news papers under the drain pan to contain the mess.
I'll also add that don't remove the radiator cap before pulling off the hose. This keeps the coolant from gushing out once you start pulling the hose off.
 
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Thanks to all for the info, especially the link to the write-up. I started the project, and I'm at the point where I'm ready to crack the T-stat housing. Luckily, I don't see any signs of coolant leakage. I haven't removed the drain bolts from the block, yet. As mentioned, they're in a tight spot. I know I can get them out, but I'm not so sure about how to get them back in, especially on the right side.

I got spillage as predicted, but it could have been worse. I caught most of it using a fair size oil pan. I tried to ease the water pump inlet hose off gradually, as suggested, but toward the end it just popped off, and out came the green stuff.

For some reason, I thought the drain bolts in the block were located lower than the connection at the water pump inlet hose. They aren't. Anyway, I'll sleep on it, and hit it again tomorrow.
 
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For the drain bolt behind the header - I bought a short swivel socket at Sears to make removal and replacement a lot easier.
 

Bones

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Do everything mentioned above, and prepare for some mess because there will be some.
 

BakerBoy

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For the drain bolt behind the header - I bought a short swivel socket at Sears to make removal and replacement a lot easier.
Here's a picture of my doing the trick mj suggests...


I found that even with a short socket and swivel joint, as I started to back out the bolt it quickly interfered with the exhaust pipe and I couldn't get the socket off the bolt head. IIRC, that problem was primarily with the right side and the position of the left drain bolt allowed the swivel joint a more straight alignment. As I recall, the left drain bolt is in a much more open area and so it can be quickly removed by finger at that point. There may be shorter sockets & swivels that would help that interference, but I only had the craftsman tools shown in the picture.

I also tried the recommendation I've read elsewhere, using a ratcheting closed-end combination wrench like this:


Although it was slow going, it did the job. For tightening both drain bolts, I used the closed-end wrench (not the socket and swivel) because I was able to feel the torque going into the bolt head and feel when the copper seal washer was being 'crushed'.

-John
 
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Honda's brilliant design engineers made it foolproof to ensure spillage. Specifically from the drain bolt. The same engineer that was responsible for the helmet locks and tank prop must have located the drain bolt. IIRC, it is right behind a header tube. Not only is it difficult to remove and replace, it will unload right into the obstruction.

For as good as the ST is, the typical Japanese engineering still shows up.

Ray
Very few design engineers have maintenance as a priority. Weight savings, getting the assigned part designed, etc. If these guys wrenched they would design things differently. I don't think Japanese engineers have cornered this market.
 
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You can also minimize the spill by not pulling the hose completely off to slow down the drainage. I spread old news papers under the drain pan to contain the mess.

What he said. I just done my thermostat and taking the lower hose off slowly will greatly minimize the mess. I only lost 1.5 cup fully due to not being extra careful. Enjoy taking the STUCK lower rad hose off.
 
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