How to: Thermostat Change

If your car is over 10 years old, or you are having problems with your car overheating or not warming up properly, it is a good idea to change your thermostat
The job of the thermostat is to block the flow of coolant to the radiator until the engine has warmed up. When the engine is cold, no coolant flows through the engine. Once the engine reaches its operating temperature, the thermostat opens.

This cooling manual may be helpful: Cooling manual

The tools you will need are:
*Some instant gasket for the drain bolt
*A 17mm socket
*12mm and 10mm sockets
*A flat head screwdriver
*A large bucket or something to drain coolant into
*New Coolant
*Thermostat: Part Number TT242-180 
*Thermostat gasket Part Number: TTG35

 

First, look under your radiator and to the left (when looking from the front), there's a bung you need to unscrew to drain the radiator, put the bucket underneath. Also take off the radiator cap to help it drain
The next thing is to remove the drain bolt from the block. (pic to the right) It will be 17mm and pretty tight if it was torqued properly last time. Use a breaker bar extension if you need to.
The coolant will come out in a rush so make sure you have the bucket in the right place.
Next, remove the coolant reservoir by pulling straight up, empty it in the bucket and give it a clean out because if it's like mine it will be full of crud.

Now remove the radiator hoses from the thermostat housing and then the housing itself by removing the two bolts. The housing will need a clean to help it mate with the new gasket properly. 
Now you need to put the new thermostat and gasket in, make sure the gasket is on the thermostat securely making sure you line up the dimples on it with the holes on the thermostat housing.
As you replace the housing and bolt it up, make sure it is aligned properly or there will be a leak, the gasket will make it fit snugly.

After tightening the bolts on the thermostat housing, you will need to reconnect the radiator hoses and replace the coolant reservoir.
Make sure you replace both the radiator bung and the one in the block, put some instant gasket on the thread of the bung in the block.
Now is a good time to do a complete coolant replacement also. Depending on the mix you may have to add water in a 50:50 ratio. Read the instructions!
Fill the coolant to the top and fill the coolant reservoir to the upper mark, replace the radiator cap.
To bleed the coolant (get all the air bubbles out of the system) you need to loosen the 10mm bleed bolt as shown at the very top right of the top picture. With this loosened, start the engine and let it idle. Coolant will flow slowly out from around the bolt, retighten the bolt once you no longer see any air bubbles coming out. Look closely as this may take a while.

Once finished, take a while to double check everything to see that there are no leaks. Keep your eye on the temperature gauge and coolant reservoir for the next few days. Depending on your car you may have to remove more things to reach the bolts, or you may not have a bleed bolt because some on some Hondas you only have to remove the radiator cap to bleed the system. This is not the case for the B16A.

 

 

This website has been gradually growing since I started it in early 2002. Originally I was simply documenting modifications and repairs to my car but I decided to publish it when I began to discover others were interested in the information. If you need help or have a how-to relating to Honda B series VTEC engines, or DA or DC2R Integras you can
email me.

While all care is taken to provide correct information, mistakes are occasionally made and I cannot be responsible for any damage that occurs to readers vehicles.