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How to Replace Thermostat and Water Passage Housings 03-07 Honda Accord

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How to Replace Thermostat and Water Passage Housings 03-07 Honda Accord

Created on: 2019-01-31

How to replace a water passage and thermostat housing on 03, 04, 05, 06, 07 Honda Accord.

  1. step 1 :Draining the Coolant
    • Have a drain pan ready
    • Turn the drain plug counterclockwise
    • Let the coolant drain
    • Turn the plug clockwise to lock it
  2. step 2 :Disconnect the Lower Radiator Hose (Engine Side)
    • Have a drain pan ready
    • Disconnect the lower radiator hose clamp with pliers
    • Disconnect the lower radiator hose
  3. step 3 :Removing the Cooling Fans and Reservoir Tank
    • Remove the 10mm bolt from the tank
    • Lift the tank out of the way
    • Disconnect the wiring harness on each side of the cooling fan
    • Unclip the wiring harness from the shroud on each side
    • From the radiator, disconnect the upper radiator hose clamp with pliers
    • Disconnect the upper radiator hose
    • Remove the three 10mm bolts from the cooling fans
  4. step 4 :Removing the Thermostat and Housing
    • Have a drain pan ready
    • Remove the three 10mm bolts from the thermostat housing
    • Unclip the alternator housing from the thermostat housing
    • Remove the thermostat and housing
  5. step 5 :Removing the Motor Mount Bracket and Aluminum Block
    • Disconnect the top 10mm bolt from the water passage housing
    • Remove the second and third 10mm bolts from the housing
    • Remove the two 17mm bolts from the motor mount bracket below the intake
    • Remove the bracket
    • Support the engine from beneath with a piece of wood and a floor jack
    • Remove the 14mm bolt from the aluminum block next to the engine block
    • Remove the 17mm bolts from the aluminum block
    • Gently tap the block with a hammer to break it free
    • Remove the 12mm bolt from the bracket next to the block
    • Remove the vertical bolt beneath the intake from the block
    • Remove the block
  6. step 6 :Removing the Water Passage Housing
    • Remove the rear fourth 10mm bolt from the water passage housing
    • Loosen the hose clamp with needle nose pliers
    • Disconnect the hose
    • Remove the water passage housing
    • Clean the mating surface of any corrosion with sandpaper
  7. step 7 :Installing the Water Passage Housing
    • Insert the water passage housing into place, using a mirror if necessary
    • Tighten the four 10mm bolt to the housing
    • Tighten the four 10mm bolts to 8.7 foot-pounds or 104 inch-pounds
    • Insert the hose to the water passage
    • Clamp the hose clamp with needle nose pliers
  8. step 8 :Installing the Motor Mount Bracket and Aluminum Block
    • Insert the aluminum block into place
    • Tighten the four 17mm bolts to the aluminum block with a drill
    • Snug up the bolts with a ratchet
    • Tighten the middle 14mm bolt to the block
    • Tighten the 12mm bolt to the bracket
    • Tighten the nut beneath the intake manifold
  9. step 9 :Installing the Thermostat and Housing
    • Clip the alternator wiring harness to the thermostat housing
    • Tighten the three 10mm bolts to the thermostat housing
    • Torque the bolts to 104 inch-pounds
    • Insert the bracket into place
    • Tighten the 17mm bolts to the bracket with a drill
    • Tighten the 17mm bolts with a socket and ratchet
  10. step 10 :Installing the Lower Radiator Hose
    • Insert the clip to the lower radiator hose
    • Put the lower hose on
    • Tighten the hose clamp
    • Lower and remove the jack from the engine
  11. step 11 :Installing the Cooling Fans and Reservoir Tank
    • Insert the fan shroud into place
    • Connect the fan shroud harnesses
    • Clip the harnesses to the fan shroud
    • Tighten the 10mm bolts to the cooling fan shroud
    • Insert the reservoir tank into place
    • Tighten the 10mm bolt to the tank
    • Install the upper radiator hose
    • Tighten the hose clamp
  12. step 12 :Refilling the Coolant
    • Fill the radiator with the appropriate 50/50 mixture
    • Leave the radiator cap off
    • Leave the funnel in the radiator
    • Place a drain pan beneath the radiator
    • Put the heat on the highest setting
    • Run the vehicle
    • Watch the air bubbles
    • Refill coolant as needed while the vehicle is running
    • Let the coolant reach operating temperature
    • Wait for the coolant level to stop dropping
    • Check for heat to come out of the vents
    • Turn the vehicle off
    • Reinstall the radiator cap
    • Top off the overflow bottle if necessary
    • Test drive the vehicle and monitor the coolant levels

Tools needed for replacement

  • General Tools

    Drain Pan

  • Materials, Fluids, and Supplies



  • Pliers, Cutters & misc Wrenches

    Needle nose pliers

  • Ratchets & Related

    Socket Extensions

    Torque Wrench


  • Sockets - Metric

    12mm Socket

    14mm Socket

    17mm Socket

    10mm Socket

Installation Video
Watch video

Hi, I'm Mike from 1A Auto. We've been selling auto parts for over 30 years.

Hey, everyone. Sue here from 1A Auto and today we have an '07 Honda Accord in our shop with a 2.4 liter. We're going to be replacing the thermostat with the housing and the water passage housing. If you need any parts for your car, click on the link below and head on over to

To drain the coolant, the drain plug is located in the center of the radiator. You'll have a cutout on the splash shield down below here. So it's just a wing butterfly spindle, so just turn it counterclockwise until the coolant comes out.

Lower hose, I'm going to take off by pulling on this middle connector. This housing on this is a plastic housing with an o-ring on the inside where it goes onto the thermostat. Grab hold of it and just pull off. Once I push that middle tab out of the way. Instead of just moving it to the next stage, I'm just going to take that clip right off. It gets pretty corroded over the years and sometimes they're really difficult to come apart. There we go. Okay.

I'm going to remove both the coolant fan and the AC fan so we can get in there easier. The directions say to remove the AC compressor and the alternator, and if I actually end up doing that, I'm going to need these out of the way anyways.

First thing I'm going to do is remove the overflow tank and take off the hose, and then there's a mounting bolt over here. It's a 10 millimeter socket. Break that free. Then I can pull up on the tank. It slides right out. Now I'm going to disconnect the fan connectors, the electrical connectors, and they're both mounted opposite to each other on the side of the actual fans shrouds. So I'm going to push down on this button and pull the tab out.

Now when this fan shroud comes up, all the harness has to be disconnected. So I'm going to grab my needle nose and just go down on the harness over there, and pull the connector right out. Now I'm going to disconnect this connector. Push down that tab. Pull the harness out.

We're going to have to disconnect the wiring harness from the actual shroud and there's several spots that it's got body clips pushed into the shroud, so we'll just use our tool to disconnect that. There's one further down. I might not able to get to that til I start to pull the fan shroud up. I'll check this side. Yep, there's one midway.

AC connector right here is on a bracket down here on the bottom corner. I just pulled it out of its bracket. Push that aside. Now we're going to just open up this top radiator hose. Get it out of the way, and let's see how much we have to move to get the shrouds out.

Okay. We've got one, three 10 millimeter sockets bolts up on top here. So we just gotta pull up on it and there's the harness right down there. The last spot that's holding us. Just take a pair of needle nose, squeeze the ears out on that. There we go.

Now the shroud's out of the way. There's three thermostat housing bolts connected to the water passage housing and it's a 10 millimeter socket. I'm going to take all three of those off. I do have a catch basin underneath. You're going to want one because this is where more of the coolant is going to come out.

The alternator harness is connected to the top of the housing. There's a little tab that the harness has a clip on. I think once we get the housing out further we can disconnect it. The thermostat housing bolts have a high rise sheathing on them and that's where it sits in the housing center so it doesn't leak. All three of them are like that. Okay, here's the last one.

Okay. Now you can see where this is connected on that housing. I don't want that to break, so I'm going to get my needle nose pliers and see if I can squeeze those tabs and let that harness connector come right out. And there is our thermostat. It's all one piece--thermostat comes with the housing.

Now we have to see what kind of visual we get of the water passage. Going to disconnect the top bolt to the housing. It's a 10 millimeter swivel socket that I'm using, quarter inch drive. Now, like I said, the directions do say take the AC compressor out, the alternator out. I'm going to give it a whirl and do something hopefully quicker and easier. There's our top bolt. I cannot physically see what I'm doing. I broke it free. I'm going to try shorter a ratchet.

Okay. That's the last to second one. Now, the furthest one in the back, which you can't even physically see at all. Not that you could see any of them. Well, the good news is I can actually feel it, so that'll help me guide the socket on.

So we've tried quite a bit of things other than taking the intake out like the directions say, and I think I can get to it if I take this top of the motor mount bracket out. So I'm going to take this bracket off. Support the engine from underneath and take that aluminum bracket where the mount attaches to the block. I've got a 17 millimeter socket.

Then I have another mounting nut over here. Actually I'm going to spray that. It's got that bracket right up. Now I'm going to take a floor jack and support the engine. I've got a piece of wood on the end of my jack. Just supporting it. 14 millimeter socket, I'm going to take this bolt out. Then what I can see, I have four mounting bolts in the back of this aluminum block to the engine block.

They look like a 17 millimeter, so I'm going to grab my 17 millimeter swivel and break them free. With a hammer I'm just going to give it a tap and see if I can break it free. And I think I just have to take this bracket off. So it was a 12 millimeter socket. Take this bracket out of the way. There's this bolt here and then there's a nut on a vertical top part of it where it screws into the bottom of the intake.

Let's see if that's out of the way enough. Perfect. Now with that housing, the motor mount housing out of the way. I've got a clear shot at that back bolt. Okay. Now I'm going to get a extension and a swivel and see if I can get a better grip on that.

So I broke the bolt free, and now I'm just going to put a swivel socket with an extension on it. See if I can use my hand and remove it. And here it is. You can see a steel tube and then there's a rubber hose and let's see how short this rubber hose is. Let's see if I can get a pair of needle nose pliers on there and pinch that clamp.

So now I've got a pair of needle nose extension pliers, and I'm going to squeeze that clamp and hopefully work it up the hose so I can disconnect it. Nice. There we go. Finally, the hose is off. Let's see if we can get this out of the way now. Whether that intake was in or out or whether the alternator's in or out, that's not going to help this specific situation right now, because neither one of them are in the way right now.

Now with the thermostat and water passage housing removed, we can see the surface and we can see the corrosion where the antifreeze was seeping out due to the little small o-ring gasket style. So I'm going to take some sandpaper, fine grit sandpaper, and I'm going to clean the surface. I really can't see so I'm going to have to just clean and take a mirror. See what I've done. There's also a hose and a steel tube that go into that housing and I took the o-ring off and I'm going to replace it. Pretty good.

I really want to get behind that pipe a lot better. I think that's where problems could lie. I'm just trying to get up in there.

All right. So now is the time to reinstall the water passage. So this part mounts flush up against the aluminum block. It's like the backside of the water pump and then the thermostat bolts to here. We have a bypass hose and a bypass tube. I put a little paste in there, silicone paste, so that I hope that the o-ring doesn't roll. I want it to stay in place and the tube to snap right down in there.

The problem is, is I can't tell if the tube's all the way down or not, so I'm going to try by looking at a bolt hole and seeing if it lines up. It definitely looks like I have to go up some more.

Okay. Let's see. This will work. So I've gotten all the bolts in, they were all flush and I'm going to torque it to the specs. It says 8.7 foot pounds, which crosses over to 104 inch-pounds and I have a quarter inch ratchet torque wrench, which is inch-pounds.

Let's see. We got one, two and the hardest one. Let's see if I can even get the socket back there. All right. Let's see if we can get the ratchet, torque wrench I would say. I am completely shocked that I could even torque those. Thankful, but shocked.

So last thing before I put the mount housing back on is I've gotta put the clamp on the hose. Well I've gotta find it. You've got to really pay attention to this because it's a heat extension clamp style, so it expands with the heat. The best way for those is to always get back in the groove they were in. If they're off, they're weak. I think I got it. I'll look with a mirror. Wow, that is right back in the groove. Perfect.

So now I'm going to put this mount back in. Let's get the bolts. So the long one went to the one closest to the housing. The other three are the same length.

I'm going to use my electric gun to get these started. Okay. Okay. Now I'm going to take my half inch, my 17 millimeter socket. I've bottomed everything out and I'm just going to snug it up.

Okay. Let's put the middle bolt in. That's a 14 millimeter. Okay. Now I've got this 12 millimeter socket bolt down here. I'm just going to snug it up. Okay. Get the horizontal nut. Tighten that.

So I'm going to put the wiring harness back through that housing. There's the clip. Snap it through. The good thing about this is the thermostat is part of this housing, so I don't have to worry about it moving on me and becoming uncentered.

Now with my 10 millimeter socket I'm just going to snug all the thermostat housing bolts down and then torque that to 104 inch-pounds. Now I can put this bracket back. This went over there. That's a 17 millimeter nut. I'm going to snug it down with the electric.

Now I'm going to put the radiator drain plug in while I have a clear shot. Get a pair of pliers and I literally snug it with a little tweak because this is plastic. I'm going to put the clip back in the lower radiator hose, so that's the first stage. That's the stage it looks like before it slides on. Make sure there's antifreeze around that o-ring to make it lubricated. Now I can just slide it right on and push down on this clamp and that's not coming off.

Now I'm clear to lower the jack and pull it out. Now we can put the shroud back in, the fan shroud. I like to put down the right side. There we go. Before I bolt anything up, I'm going to reconnect all the connectors and put the harnesses clips back into the little mounting holes. Connector for this side fan. The AC harness, I'm going to put right back in that bracket, and now I can line up the bottom and then bolt it in. Okay. There we go. Beautiful. Three mounting bolts on the top. 10 millimeter socket.

Make sure all the fans are plugged in. That's not something you want to find out later on. Let's put the reservoir tank on. That's got a little guide right down there and it's got a slotted sleeve over here. There you go. Start the bolt and put the overflow hose on. 10 millimeter socket.

Now we can put the upper radiator hose on and set the clamp right where it was. This has a spring style clamp so it ended up locking into place, which is a pretty good thing. Now I'll just pop it out. I'm going to reline that up because I know I can be kind of meticulous. And there that is. I think we're ready for the coolant.

Now I've got my vacuum machine on here. I'm going to vacuum the coolants to make sure there's no air in the system and then we can add the coolant. So I've cleaned the bucket prior to draining it and its new coolant, so I'm just going to take it right from here. If I don't wear it first. That's the way the day has been.

So I can take the vacuum gauge off and now I'm going to connect my funnel. This tool is awesome--you can get it at 1A Auto. It's a good way to stop it from overflowing, hitting the ground and you can watch it actually burp. Instead of putting the cover on and going through the overflow, you can actually let this car run for 40-45 minutes it takes for the thermostat to open, and if you leave at a decent level, you can watch it go down or rise up with the heat. And then if there's air pockets, it'll burp and fly right down.

Run the vehicle 'til you'll see it burp and the coolant fans come on. So to disconnect the coolant burper, I would put the stopper in and some coolant's going to drip out. That's going to happen. And then I'll disconnect this end. Install the radiator cap. And what I like to do is, it's a little bit below minimal, but this car is warm. The thermostat's opened, so I'm going to raise that level up to the high area. I'm going to put the rest of this coolant right in there. Well, most of it. Now I'm going to rinse this down and road test it.

Thanks for watching. Visit us at for quality auto parts, fast and free shipping, and the best customer service in the industry.

Tools needed for replacement:

    General Tools

  • Drain Pan

  • Materials, Fluids, and Supplies

  • Sandpaper
  • Anti-Freeze

  • Pliers, Cutters & misc Wrenches

  • Needle nose pliers

  • Ratchets & Related

  • Socket Extensions
  • Torque Wrench
  • Ratchet

  • Sockets - Metric

  • 12mm Socket
  • 14mm Socket
  • 17mm Socket
  • 10mm Socket

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