Honda Accord: How to Replace Thermostat

This article applies to the Honda Accord (1990-2002).

An important part of a car's cooling system is the thermostat. If your thermostat is bad, then you are probably experiencing overheating issues, which are dangerous because they can lead to an engine damage. If you suspect that you need a thermostat replacement, then be sure to read this article. This article will go over the few steps needed to get this job done.

Step 1 – Drain coolant from radiator

First thing you need to do is drain the coolant from the radiator. You will need to do this so that when you remove the thermostat, you wont have coolant spilling all over your engine bay and driveway. You have to remove the drain plug from underneath the radiator. In most cases it will be a plastic drain plug like a wing nut. Turn it counterclockwise. Make sure to place a bucket underneath the plug, so that you can collect all the old coolant. Around two gallons should drain out. If your coolant flow seems slow, remove the radiator cap and coolant reservoir cap to speed up the process. Also, consider gently squeezing any radiator hoses that you can reach to coax any residual stuck coolant out.

Step 2 – Remove air intake

On the front and back of the air intake box there are 10mm screws. Remove both of these screws. You will probably need the extension for the socket wrench. After that, remove the breather hose from the intake tube. Unplug the mass air flow sensor, so that you don't pull on it by accident. Remove the clamp that clamps the intake tube to the throttle body. You will need a Phillips head screwdriver to do that. Hold on to the screw, so that it doesn't fall after you completely loosen it. Lastly, the throttle cable might be clipped onto the intake tube, so undo that. Now you can remove the entire intake box and tube.

Step 3 – Remove three 10mm bolts

One of these bolts is for the support bracket of the wiring harness, which is to the left of the thermostat. Once you remove that bolt you can move the bracket out of the way. The other two bolts are on the bottom and top of the thermostat, which are actually holding the thermostat in place. You will also want to remove the fan switch, which is easy to disconnect. The two 10mm bolts holding the thermostat housing in place might be a tight fit for your wrench.

Step 4 – Install new thermostat

Once the thermostat housing bolts are removed, you can proceed to pushing down on the housing with your hands. It should come loose. Once you have nudged it loose, continue to nudge the actual thermostat loose from the thermostat housing. When installing the new thermostat, make sure to put the passing position on the top. In general, you should have noted the placement of the old one. Also, read the instructions that come with the new thermostat for proper positioning. It is important to get this correct. Once you have it correctly placed, set it into the housing and put the cover over it (the part with the lower radiator hose still connected to it). Now you can re-install the two housing bolts. First get the top bolt in, but wait to tighten it in order to secure the bottom bolt. Then you can tighten both bolts all the way.

Step 5 – Re-install

Get the two thermostat housing bolts tightened. Then, re-install the wiring harness support bracket. Plug in the fan switch. After that, go back and install the air intake. Finally, you want to tighten the radiator drain plug, and pour in some fresh coolant. If necessary, you can do a quick bleed of the cooing system by topping off the coolant, and running the motor with the radiator cap off. Then, topping off as necessary. You have now completed the job.

Featured Video: Honda Accord Thermostat Replacement

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