1997 Honda Accord changed thermostat
CheeseHead1
09-30-2012, 10:13 PM
Howdy all,
I just changed the thermostat on my 1997 Honda Accord and wanted to share my experiences. The engine is a 4-cylinder engine 16-valve, sorry I'm not sure exactly what the engine size or name is.
The thermostat was a real pain to change, mostly because lots of fasteners had rusted in place.
I purchased a "fail-safe" thermostat at Auto Zone, fail-safe because after aging it is designed to fail in the open position (so the car would run slightly cool). (If it failed in the closed position, the car would be likely to overheat - bad). I also purchased a thermostat gasket at Auto Zone. I purchased coolant they recommended at Auto Zone, I think it was Peak 1.
My general philosophy before tackling a new car repair project is to buy everything I might possibly need and keep the receipt - then return it afterwards if I didn't need it. In that spirit I also purchased two radiator hoses (upper and lower) and 8 screw-on clamps for the radiator hosts "just in case" (I wasn't sure exactly which size would fit, thus purchased 8 instead of just 4).
Also if you shop at Auto Zone, sign up for a frequent customer card. This is not a commercial, I am not affiliated with Auto Zone. If you make five purchases $25 or over in a certain time frame, then somehow you get a $25 credit for a future purchase (I have not personally managed this yet, but it's a worthy goal ;-)
The drain plug is easily accessible, center front, below the radiator (duh!), look in the open rectangle in the plastic under guard, the end is white. This was described nicely in the owners manual. Access it from the bottom of the car.
Don't rely on my post for all the safety precautions, read a manual: Coolant is hot, disconnect negative battery connection, don't open radiator cap when hot, open radiator cap before draining, coolant is bad for your skin, don't drink the coolant, don't leave coolant where pets can drink it, etc.
I purchased a nice catch basin at Auto Zone, it holds five gallons and is open on top, but has a handle at one end and a pour spout at the other end. It's about 4-6" tall, tall enough to hold a lot but low enough to fit nicely under the Accord when it's on the ground.
The upper radiator hose led to a housing on the front side of the engine. I was hoping the thermostat was in there. Nope! That would be too easy. :crying:
In hindsight that front housing looks a little small to hold the thermostat. If you do open that housing, be sure to reconnect it in the same order. There is a bracket that connects to the housing, it connects to the front of the housing! If you connect it inside the housing, you will get a bad leak. Don't ask me how I know this. :banghead:
While we had the upper hose half-way off, we went ahead and changed it. Changing the hose was straightforward. There are spring clips on each end. Use a plier to squeeze the two tabs of the spring clip, then move the clip out of the way (toward the center of the hose) by pushing/pulling with the pliers and pushing on the bottom of the clip with your free hand as well. Then use a big pair of pliers to twist the old hose free, be sure not to squish/dent/deform the connector underneath the hose in the process. Once it is rotating freely, you should be able to push it off of the connector.
OK, so the thermostat must be where the lower hose connects to the engine. It winds up and toward the back of the engine (closer to the passenger compartment). It's a tight space and difficult to work in.
You can get more space by freeing up a big black tube that runs diagonally across the engine compartment, it's an air intake tube that runs from the air filter to the air intake (I think, I'm not an expert).
The near end of the tube has a spring that runs around it, you can just get a screwdriver under that end and pry it free. The tube is flexible and will bend quite a bit with no apparent ill effects.
The other end of the tube is a straightford screw/clamp. Turning the screw opens the clamp enough to remove the other end of the tube.
There is one vaccuum tube connected to the big black tube, remove it and take the clamp off. (Otherwise the clamp may fall off later during the job...) There are a few other wires/tubes that clip into the big black tube, just remove them. That will give you room to work.
The thermostat housing has two main bolts that hold it in, plus a third smaller bolt that holds a bracket in place. All are 10 mm bolts. The bracket supports a tube, also part of the wiring harness. The two main bolts are longer, the bolt that holds the bracket is shorter.
The bracket was blocking access to the smaller bolt that holds it. There is another bolt/nut combination on the bracket that I was unable to remove. So I bent the bracket up a little out of the way. Then I was able to access and remove the smaller bolt that holds the bracket. I think I used a 1/4" drive and a deep 10 mm socket.
The upper main bolt on the thermostat housing was easily accessible.
The lower main bolt on the thermostat housing was a challenge. It was very difficult to see, feel or get a wrench on. I soaked it good with PB Blaster and let it sit for a while. I was able to get a small 10mm box end socket on it and turn it. Removing was a pain, I was not able to get a socket on it. Had to use the box end wrench slowly 1/12 turn at a time and finally was able to get it finger loose, then remove with my fingers.
Installing the replacement thermostat was straightforward. Read the manual. The little dangly/hole part of the thermostat goes near the top. I think it may be slotted, mine fit in very happily.
I used the new gasket but did not use any additional gasket material (no form-a-gasket). Didn't have any problems with leaks in that area.
Do not overtighten the bolts when reassemblying. My manual called for around 104 INCH-pounds which is not much torque.
We had already drained the radiator before removing the thermostat. Then flushed the radiator by adding a cleaner product. Ran the vehicle about 15 minutes. Drained it. Filled with water. Ran 5 minutes. Drained it again. Filled with coolant.
When filling with coolant I believe it had about a 1.5 gallon capacity, but it was only taking about 3/4 gallon when we filled it. So I believe the system was about 50% full with water already due to the flushing we had done. So I added pure coolant to the radiator - after mixing with all the water that was trapped in the system, hopefully it will have about the right mix.
I did add 50-50 mix to the coolant overflow bottle.
We also removed and cleaned the coolant overflow bottle during the project - that makes it much easier to see the level on the bottle now. They have some nice grease-cutting hand washing solution at the shop I was working at, we soaked the bottle with the stuff and shoved in a few rags. Shook the heck out of it. Poured out and repeated a few times, the bottle came out great - almost totally clean, still a few dirty patches stuck in the bottom. But 1000% better than when we started. This included soaking the bottle overnight with the cleaning solution in it.
The spring clips on the old upper hose looked good, so we re-used them on the replacement upper hose.
The lower hose - we decided not to tackle during this project. Although we already had one end free, the other end connected to the radiator looked very difficult to access. I'm guessing that's a project that will require some disassembly to access - maybe removing the main radiator fan?
If you have problems with leaks afterwards, you might want to have some high-temperature Permatex (form-a-gasket) handy.
Overall the project was a lot more of a pain than I thought it would be - mostly due to rusty hardware. Also due to the thermostat being toward the rear of the vehicle, harder to reach and a cramped space to work in.
The vehicle did come up to normal operating temperature much better after the replacement, so that's good. I think the old thermostat was stuck open or mostly open. The symptom I was treating is that the vehicle would only come up to operating temperature slowly, or if very cold during the winter (I live in Wisconsin) it would not come up to operating temperature. Then if I stopped, it would warm up - but cool back down when moving at speed. This is a problem in Wisconsin, it made the heat very unreliable during the winter, especially on the colder days! So hopefully we're looking forward to having some good heat in the vehicle this winter. :smile:
I just changed the thermostat on my 1997 Honda Accord and wanted to share my experiences. The engine is a 4-cylinder engine 16-valve, sorry I'm not sure exactly what the engine size or name is.
The thermostat was a real pain to change, mostly because lots of fasteners had rusted in place.
I purchased a "fail-safe" thermostat at Auto Zone, fail-safe because after aging it is designed to fail in the open position (so the car would run slightly cool). (If it failed in the closed position, the car would be likely to overheat - bad). I also purchased a thermostat gasket at Auto Zone. I purchased coolant they recommended at Auto Zone, I think it was Peak 1.
My general philosophy before tackling a new car repair project is to buy everything I might possibly need and keep the receipt - then return it afterwards if I didn't need it. In that spirit I also purchased two radiator hoses (upper and lower) and 8 screw-on clamps for the radiator hosts "just in case" (I wasn't sure exactly which size would fit, thus purchased 8 instead of just 4).
Also if you shop at Auto Zone, sign up for a frequent customer card. This is not a commercial, I am not affiliated with Auto Zone. If you make five purchases $25 or over in a certain time frame, then somehow you get a $25 credit for a future purchase (I have not personally managed this yet, but it's a worthy goal ;-)
The drain plug is easily accessible, center front, below the radiator (duh!), look in the open rectangle in the plastic under guard, the end is white. This was described nicely in the owners manual. Access it from the bottom of the car.
Don't rely on my post for all the safety precautions, read a manual: Coolant is hot, disconnect negative battery connection, don't open radiator cap when hot, open radiator cap before draining, coolant is bad for your skin, don't drink the coolant, don't leave coolant where pets can drink it, etc.
I purchased a nice catch basin at Auto Zone, it holds five gallons and is open on top, but has a handle at one end and a pour spout at the other end. It's about 4-6" tall, tall enough to hold a lot but low enough to fit nicely under the Accord when it's on the ground.
The upper radiator hose led to a housing on the front side of the engine. I was hoping the thermostat was in there. Nope! That would be too easy. :crying:
In hindsight that front housing looks a little small to hold the thermostat. If you do open that housing, be sure to reconnect it in the same order. There is a bracket that connects to the housing, it connects to the front of the housing! If you connect it inside the housing, you will get a bad leak. Don't ask me how I know this. :banghead:
While we had the upper hose half-way off, we went ahead and changed it. Changing the hose was straightforward. There are spring clips on each end. Use a plier to squeeze the two tabs of the spring clip, then move the clip out of the way (toward the center of the hose) by pushing/pulling with the pliers and pushing on the bottom of the clip with your free hand as well. Then use a big pair of pliers to twist the old hose free, be sure not to squish/dent/deform the connector underneath the hose in the process. Once it is rotating freely, you should be able to push it off of the connector.
OK, so the thermostat must be where the lower hose connects to the engine. It winds up and toward the back of the engine (closer to the passenger compartment). It's a tight space and difficult to work in.
You can get more space by freeing up a big black tube that runs diagonally across the engine compartment, it's an air intake tube that runs from the air filter to the air intake (I think, I'm not an expert).
The near end of the tube has a spring that runs around it, you can just get a screwdriver under that end and pry it free. The tube is flexible and will bend quite a bit with no apparent ill effects.
The other end of the tube is a straightford screw/clamp. Turning the screw opens the clamp enough to remove the other end of the tube.
There is one vaccuum tube connected to the big black tube, remove it and take the clamp off. (Otherwise the clamp may fall off later during the job...) There are a few other wires/tubes that clip into the big black tube, just remove them. That will give you room to work.
The thermostat housing has two main bolts that hold it in, plus a third smaller bolt that holds a bracket in place. All are 10 mm bolts. The bracket supports a tube, also part of the wiring harness. The two main bolts are longer, the bolt that holds the bracket is shorter.
The bracket was blocking access to the smaller bolt that holds it. There is another bolt/nut combination on the bracket that I was unable to remove. So I bent the bracket up a little out of the way. Then I was able to access and remove the smaller bolt that holds the bracket. I think I used a 1/4" drive and a deep 10 mm socket.
The upper main bolt on the thermostat housing was easily accessible.
The lower main bolt on the thermostat housing was a challenge. It was very difficult to see, feel or get a wrench on. I soaked it good with PB Blaster and let it sit for a while. I was able to get a small 10mm box end socket on it and turn it. Removing was a pain, I was not able to get a socket on it. Had to use the box end wrench slowly 1/12 turn at a time and finally was able to get it finger loose, then remove with my fingers.
Installing the replacement thermostat was straightforward. Read the manual. The little dangly/hole part of the thermostat goes near the top. I think it may be slotted, mine fit in very happily.
I used the new gasket but did not use any additional gasket material (no form-a-gasket). Didn't have any problems with leaks in that area.
Do not overtighten the bolts when reassemblying. My manual called for around 104 INCH-pounds which is not much torque.
We had already drained the radiator before removing the thermostat. Then flushed the radiator by adding a cleaner product. Ran the vehicle about 15 minutes. Drained it. Filled with water. Ran 5 minutes. Drained it again. Filled with coolant.
When filling with coolant I believe it had about a 1.5 gallon capacity, but it was only taking about 3/4 gallon when we filled it. So I believe the system was about 50% full with water already due to the flushing we had done. So I added pure coolant to the radiator - after mixing with all the water that was trapped in the system, hopefully it will have about the right mix.
I did add 50-50 mix to the coolant overflow bottle.
We also removed and cleaned the coolant overflow bottle during the project - that makes it much easier to see the level on the bottle now. They have some nice grease-cutting hand washing solution at the shop I was working at, we soaked the bottle with the stuff and shoved in a few rags. Shook the heck out of it. Poured out and repeated a few times, the bottle came out great - almost totally clean, still a few dirty patches stuck in the bottom. But 1000% better than when we started. This included soaking the bottle overnight with the cleaning solution in it.
The spring clips on the old upper hose looked good, so we re-used them on the replacement upper hose.
The lower hose - we decided not to tackle during this project. Although we already had one end free, the other end connected to the radiator looked very difficult to access. I'm guessing that's a project that will require some disassembly to access - maybe removing the main radiator fan?
If you have problems with leaks afterwards, you might want to have some high-temperature Permatex (form-a-gasket) handy.
Overall the project was a lot more of a pain than I thought it would be - mostly due to rusty hardware. Also due to the thermostat being toward the rear of the vehicle, harder to reach and a cramped space to work in.
The vehicle did come up to normal operating temperature much better after the replacement, so that's good. I think the old thermostat was stuck open or mostly open. The symptom I was treating is that the vehicle would only come up to operating temperature slowly, or if very cold during the winter (I live in Wisconsin) it would not come up to operating temperature. Then if I stopped, it would warm up - but cool back down when moving at speed. This is a problem in Wisconsin, it made the heat very unreliable during the winter, especially on the colder days! So hopefully we're looking forward to having some good heat in the vehicle this winter. :smile:
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