Type 2 Coolant...
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From: Kenton, TN
As with many Honda's....the flow of coolant is from the bottom of the rad to the top. So pouring water from the top will "back flush" the rad.
At the end of the day....an '09 and just the fact you are going to change the coolant, don't loose any sleep.
At the end of the day....an '09 and just the fact you are going to change the coolant, don't loose any sleep.
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Almost A Senior Member
Joined: Jun 2011
Posts: 329
If I'm just idling to get the car up, how long do you guys think it should take to warm it up to op temp and totally the whole bleeding process?
Can I put the car in neutral, put the parking brake on and rev the car safely without doing any damage?
Right now I'm estimating 30 minutes of idling total up to one hour. Can anyone offer a timeline of the bleeding process to know what I should be looking for in terms of how hot the rad hoses should be, which rad hoses should get hot and when?
Can I put the car in neutral, put the parking brake on and rev the car safely without doing any damage?
Right now I'm estimating 30 minutes of idling total up to one hour. Can anyone offer a timeline of the bleeding process to know what I should be looking for in terms of how hot the rad hoses should be, which rad hoses should get hot and when?
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Joined: May 2011
Posts: 197
I usually put the car in park run it around 2k rpms until the fans kick on twice takes about 15 minutes with the cap off. This is for a 96 accord. Then put the cap back on and drive it around close to home and see if it accelerates normal, never had a case where it did not after doing the above.
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Joined: Jul 2011
Posts: 1,008
From: Denver
I think it's bottom to top; the lower radiator hose is cold until the thermostat opens up. That tells me that coolant is flowing from the lower hose into the radiator. Counterintuitive, I think I found out why a few weeks ago when surfing at The Truth About Cars:
Phil’s Podium Of The Automotive Pure:
Ten Trick Technologies That Changed the Automotive Maintenance & Repair Scene — Part Three
By Phil Coconis on July 14, 2012
The Reverse-Flow Cooling System:
Like a musical style I’d never heard before, I remember seeing this idea on Blue Propeller offerings in the very early ‘80’s, and wondering if it was really necessary, even though it didn’t seem to add to the complexity of the systems extant at the time.
Of course, after researching the whole thing, I had to conclude that a “better mousetrap” HAD really been invented!
This turned out to be especially true for engines with aluminum cylinder heads and cast iron blocks, where the combination of typical operating temperatures along with these metal’s different reaction to heating and cooling led to problems in the head gasket area.
Reversing the coolant flow routs the cooled coolant from the radiator outlet to the typically hotter-running head first, with that transferred heat now warming up the typically cooler-running block, thereby more closely matching the operating temperatures of the two!
The results are increased engine durability (regardless of the metals used in its construction), better warm-up driveability, AND lower exhaust emissions, to boot.
Everyone wins here!
Ten Trick Technologies That Changed the Automotive Maintenance & Repair Scene — Part Three
By Phil Coconis on July 14, 2012
The Reverse-Flow Cooling System:
Like a musical style I’d never heard before, I remember seeing this idea on Blue Propeller offerings in the very early ‘80’s, and wondering if it was really necessary, even though it didn’t seem to add to the complexity of the systems extant at the time.
Of course, after researching the whole thing, I had to conclude that a “better mousetrap” HAD really been invented!
This turned out to be especially true for engines with aluminum cylinder heads and cast iron blocks, where the combination of typical operating temperatures along with these metal’s different reaction to heating and cooling led to problems in the head gasket area.
Reversing the coolant flow routs the cooled coolant from the radiator outlet to the typically hotter-running head first, with that transferred heat now warming up the typically cooler-running block, thereby more closely matching the operating temperatures of the two!
The results are increased engine durability (regardless of the metals used in its construction), better warm-up driveability, AND lower exhaust emissions, to boot.
Everyone wins here!
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Joined: May 2010
Posts: 11,834
From: Kenton, TN
I've been wrong before....took a quick look at the manual I have for the 08.....could have read it wrong. Need to read it more, sorry.
I was just going with "which" side the "pill" on the t-stat is pointing. Since the "pill" is the temp sensitive side of the part....you'd want that on the side of the "push" of hot coolant, thus opening the t-stat and alowing coolant to flow, or not, depending on how hot the coolant being pushed towards it is........more reading needed.
EDIT: If the coolant flow was going to the "face" of the t-stat and only able to get to the "pill" via the jiggle pin then I would think there could be an issue with the t-stat controlling the temp in the 190~210 range.
I was just going with "which" side the "pill" on the t-stat is pointing. Since the "pill" is the temp sensitive side of the part....you'd want that on the side of the "push" of hot coolant, thus opening the t-stat and alowing coolant to flow, or not, depending on how hot the coolant being pushed towards it is........more reading needed.
EDIT: If the coolant flow was going to the "face" of the t-stat and only able to get to the "pill" via the jiggle pin then I would think there could be an issue with the t-stat controlling the temp in the 190~210 range.
Last edited by poorman212; Nov 12, 2012 at 08:25 PM.
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Almost A Senior Member
Joined: Jun 2011
Posts: 329
Okay, once and for all, coolant flow direction... - Page 2 - K20A.org .:. The K Series Source . Honda / Acura K20a k24a Engine Forum
Looks like it's the other way around, it flows out of the block through the top, flows down radiator, when thermostat opens it sucks it in through the bottom of the block, circulates up and repeats. But "water outlet" could be subjective depending on whether it's an outlet viewed from the radiator's POV or the block's POV. Damn this is confusing.
Here's what I think is happening:
When I look down I can see the t-stat is on block and lower hose is connected to it and it is almost vertical to reach the bottom of the rad. When you drain and fill the rad, the bottom hose since it's vertical should have a lot of air. Think of a cave under water that has an air pocket so you can actually swim under water and surface into the cave because it is an air pocket. So I think there's going to be an air pocket there. The upper hose is flat so that will fill evenly and there won't be an issue there. I think that's why upper hose gets warm, it's already fluid filled so it conducts heat even though coolant isn't circulating. The lower is air filled so it stays cool. Once the t-stat opens it sucks the coolant from the radiator through bottom and the air pocket moves into the block (
) since fluid is now in the lower hose it gets warm. What I'm confused of is once the air is in the block, how does it get out? I don't think there is coolant in the cylinder head, only in the jacket around the cylinders in the block. So let's say the air is in the block now, so the air is above the coolant and the air covers the upper half of the block water jacketting, how does that air get out?
The only way I can see is if the rad cap is open, the system is open so there's somewhere for air to go since it's not pressurized or vacuum sealed. As coolant continues to flood the cylinder it will raise the level of coolant and push the air out of the cylinder similar to how when you fill a bottle of water since the cap is open the air continues to move out as water displaces it. If the car is on an incline, the air will move where it can, from the top of the block through the upper rad hose as the block filles and keep moving up the rad hose until it leaves through the filler neck. If the rad cap were on, I think the air would be trapped there forever. This at least gives me some confidence that I can get the air out of the block, if I can get it out without overheating the engine first I would be golden.
If I'm wrong and coolant does flow through the cylinder head, meh, I don't know what the head coolant passages look like. I think actually the upper rad hose might be connected to the head and not the block then since the head is the highest point so nothing changes then. It simply fills the block until it reaches and fills the head pushing the air out of the head through the upper hose and out the filler neck. I don't think Honda would have designed this to trap air. It would make their own coolant change procedures dangerous.
I think then what I have to do is once the t-stat opens, squeeze the lower hoses to force the air from the bottom of the hose up and move all of the air into the block and head. Then squeeze the upper rad hose from engine to rad direction to move the air bubbles along so they leave the filler neck.
Looks like it's the other way around, it flows out of the block through the top, flows down radiator, when thermostat opens it sucks it in through the bottom of the block, circulates up and repeats. But "water outlet" could be subjective depending on whether it's an outlet viewed from the radiator's POV or the block's POV. Damn this is confusing.
Here's what I think is happening:
When I look down I can see the t-stat is on block and lower hose is connected to it and it is almost vertical to reach the bottom of the rad. When you drain and fill the rad, the bottom hose since it's vertical should have a lot of air. Think of a cave under water that has an air pocket so you can actually swim under water and surface into the cave because it is an air pocket. So I think there's going to be an air pocket there. The upper hose is flat so that will fill evenly and there won't be an issue there. I think that's why upper hose gets warm, it's already fluid filled so it conducts heat even though coolant isn't circulating. The lower is air filled so it stays cool. Once the t-stat opens it sucks the coolant from the radiator through bottom and the air pocket moves into the block (
) since fluid is now in the lower hose it gets warm. What I'm confused of is once the air is in the block, how does it get out? I don't think there is coolant in the cylinder head, only in the jacket around the cylinders in the block. So let's say the air is in the block now, so the air is above the coolant and the air covers the upper half of the block water jacketting, how does that air get out?The only way I can see is if the rad cap is open, the system is open so there's somewhere for air to go since it's not pressurized or vacuum sealed. As coolant continues to flood the cylinder it will raise the level of coolant and push the air out of the cylinder similar to how when you fill a bottle of water since the cap is open the air continues to move out as water displaces it. If the car is on an incline, the air will move where it can, from the top of the block through the upper rad hose as the block filles and keep moving up the rad hose until it leaves through the filler neck. If the rad cap were on, I think the air would be trapped there forever. This at least gives me some confidence that I can get the air out of the block, if I can get it out without overheating the engine first I would be golden.
If I'm wrong and coolant does flow through the cylinder head, meh, I don't know what the head coolant passages look like. I think actually the upper rad hose might be connected to the head and not the block then since the head is the highest point so nothing changes then. It simply fills the block until it reaches and fills the head pushing the air out of the head through the upper hose and out the filler neck. I don't think Honda would have designed this to trap air. It would make their own coolant change procedures dangerous.
I think then what I have to do is once the t-stat opens, squeeze the lower hoses to force the air from the bottom of the hose up and move all of the air into the block and head. Then squeeze the upper rad hose from engine to rad direction to move the air bubbles along so they leave the filler neck.
Last edited by MessAround; Nov 13, 2012 at 12:37 AM.
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From: Wisconsin
All good, except the thermostat has a little rattle-pin which is like a check-valve to allow air to escape through a closed T-stat. When I had a 2003 Accord I simply filled at the radiator and it took care of itself.
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From: United States
It should flow from the water outlet on the head to the top of the radiator, through the radiator and back out the lower radiator hose. The 8th gen Accord service manual shows the hose from the "water outlet" going to the top of the radiator.
The upper radiator hose is warm/hot first, as the heated coolant from the engine is going to the radiator. Thus, the lower radiator hose is not warm/hot like the upper hose until the thermostat opens.
The upper radiator hose is warm/hot first, as the heated coolant from the engine is going to the radiator. Thus, the lower radiator hose is not warm/hot like the upper hose until the thermostat opens.