CHANGING THE THERMOSTAT
by John Mosko

Changing out a faulty thermostat isn’t a difficult job, but there are a few little things you need to know going in, and a couple of precautions you should always take. In this quick examination of the procedure, we’ll discuss the tools you need, the steps to take, and how to finish the job right. Let’s get started.

What we need:
Either a flat head screwdriver, an appropriately sized nut driver, or a ratchet/socket for the hose clamps.
You will also likely need the ratchet and socket for the thermostat housing bolts.
A drip pan to catch any fluid.
Potentially a flat scraper to remove any of the old gasket.
And a rag or two is always a good idea…

Once we get rolling here, the whole process shouldn’t take much more than about thirty minutes. But before we start, I’ll give you my quick thoughts on swapping out the thermostat. I tend to always replace it before getting into more advanced troubleshooting and dagnostics with the water pump and other parts that could have failed, simply because the thermostat is so simple and cheap to change. The part shouldn’t cost you more than about $10 and for the 30 minutes it takes to switch it out, you may well have solved your problem.

So with my obvious affinity for taking the quick route and changing the thermostat, here’s how to do it.

First, Find the Thermostat, and Remove it
Almost all thermostats are located on the top radiator hose (with a rare few being on the bottom) and you’ll get to it by simply using the tools you have gathered to disconnect the top radiator hose from the engine. Make sure you have your drip pan in place underneath your work area to catch any mess, and once the hose is loose, pull it away from the engine.

Once you have pulled the hose from the engine, you will need to remove the bolts which hold the thermostat housing in place. Once you have done so, simply remove the housing and lift out the thermostat.

Next, Install the New Thermostat
Unless you turn out to be incredibly lucky, there is likely some portion of the old gasket still lingering around from where you just removed the thermostat. Use one of your rags to plug the hole, and remove any old gasket with the flat scraper. Once you have everything as clean as possible, we’ll install the new thermostat.

To do so, simply set the new gasket in place and install the thermostat with the power unit pointed towards the block. Once you have it in place, replace the bolts you previously removed, and snug it into place.

Finally, Finish the Job
One the thermostat is tightly in place, replace the hose and cleamp you removed previously. If your drip pan caught a good deal of fluid, you may need to add a bit to get the system back to full. You can re-use what’s in the pan, but if you have some fresh coolant, that is always preferable.

And that folks is just about all there is to it. If you get stuck at any point in the process, or have some questions about diagnosing the problem from the get go, visit our Auto Repair Forums and get a quick answer to your question.