Last winter, my buddy’s 2013 Honda Civic started acting up big time. The heater blew cold air even after driving for miles, and the engine stayed chilly way too long. Turned out the thermostat was stuck open, wasting gas and making every ride freezing. We fixed it ourselves in the garage over a weekend, and the car ran perfect after. If your Civic is overheating or not warming up right, swapping the thermostat can solve it quick. Let’s dive into how to do it without any headaches.
Key Takeaways:
Park the car on a flat spot and let the engine cool completely before starting. Gather tools like a 10mm socket, ratchet, pliers, drain pan, new thermostat with gasket, and fresh Honda coolant. Drain the coolant from the radiator petcock until it’s below the thermostat level. Follow the lower radiator hose to the engine block to find the thermostat housing. Remove any ground wires or sensors in the way, then unbolt the housing and pull out the old thermostat. Clean the surfaces well, install the new thermostat with the spring side toward the engine and jiggle valve at the top, then bolt everything back snug. Refill with coolant, bleed the air by running the engine with the heater on max, and top off as needed.
Getting Ready for the Job
First off, make sure your Civic is parked on level ground and the engine is stone cold. Touching hot coolant is no joke, it can burn bad. Pop the hood and take off the radiator cap to release any pressure, but only if it’s cool. Grab a big drain pan because some coolant will spill, and you want to catch it to keep the driveway clean.
Next, look under the car at the bottom of the radiator on the driver’s side. There’s a little plastic petcock valve there. Turn it slowly to open and let the coolant drain out. You don’t need to empty everything, just get the level below where the thermostat sits so less mess when you open the housing. While it’s draining, round up your stuff: a new OEM thermostat if you can, because cheap ones fail fast, plus coolant, rags, and tools.
Once drained, close the petcock tight. Now you’re set to locate the thermostat. Trace the thick lower radiator hose from the radiator back to the engine. It connects right to the thermostat housing, a metal or plastic piece bolted to the block. On the 2013 Civic with the 1.8L engine, it’s down low near the transmission side, kinda tucked but reachable without jacking the car up much.
- Drain coolant safely into a pan
- Use OEM parts for best results
- Keep rags handy for spills
- Work only on a cold engine
Locating and Accessing the Thermostat
Start by getting a good look under the hood. The thermostat housing is where that lower radiator hose clamps on to the engine block. It’s usually got two or three bolts holding it, and there might be a sensor plugged in or a ground wire attached. Clear any junk out of the way, like moving wires gently aside.
Then, loosen the hose clamp on the lower radiator hose with pliers or a screwdriver. Twist and pull the hose off the housing, but have your drain pan ready because leftover coolant will pour out. Wiggle it free without yanking too hard, hoses can crack if old. If it’s stuck, a little twist helps.
After the hose is off, check for any electrical stuff. There’s often a green plug for the temp sensor, unplug it carefully by pressing the tab. Also, a ground wire might be bolted there with a 10mm, remove that too. Now the housing is exposed, and you can see the bolts clearly.
- Follow lower hose to housing
- Loosen clamp and remove hose carefully
- Unplug sensor and remove ground wire
- Catch any spilling coolant
Removing the Old Thermostat
With everything cleared, grab your 10mm socket and ratchet. There are usually two or three bolts holding the housing to the engine block. Loosen them evenly so the housing doesn’t bind. Once loose, pull the housing straight off, it might stick a bit from the old gasket.
Inside, you’ll see the old thermostat sitting there. Note how it’s oriented, the spring side goes toward the engine, and there’s a little jiggle valve or bleed hole that needs to point up at 12 o’clock when reinstalled. Pull the old one out, it might have an O-ring or gasket stuck to it.
Clean the mating surfaces real good. Scrape off any old gasket bits with a plastic scraper so nothing rough is left. Wipe it down with a rag, make sure no crud falls into the engine opening. Check the new thermostat against the old one to confirm it’s the right part.
- Unscrew housing bolts evenly
- Note thermostat orientation before removal
- Clean surfaces thoroughly
- Inspect new part matches old
Installing the New Thermostat
Take your new thermostat and make sure the O-ring or gasket is in place, most come with it. Position it just like the old one, spring bulging into the engine, jiggle valve straight up. That valve helps bleed air later, so get it right or you’ll have bubbles causing hot spots.
Set the housing over it carefully, lining up the bolts. Hand thread the bolts first to avoid cross threading, then snug them down with the socket. Don’t crank super tight, just firm, like 10-15 ft-lbs if you have a torque wrench, but finger tight plus a quarter turn works if not.
Reattach the ground wire if there was one, and plug in the sensor until it clicks. Slide the lower radiator hose back on and tighten the clamp good, but not stripping it. Double check everything is connected before moving on.
- Position new thermostat correctly
- Hand start bolts then tighten evenly
- Reconnect wires and sensor
- Secure hose clamp properly
Refilling Coolant and Bleeding Air
Pour fresh Honda Type 2 coolant into the radiator, 50/50 mix with distilled water is best. Fill to the top, then start the car with the heater on full blast hot. Let it idle and watch the level drop as air burps out.
Squeeze the upper and lower radiator hoses gently to help push air bubbles toward the radiator. Keep topping off coolant as it drops. When the thermostat opens, you’ll feel the upper hose get hot suddenly, and more air might come out. Rev the engine a bit to 2000 rpm now and then to move things along.
Run it until the fan kicks on a couple times, then shut off and let cool. Check for leaks around the housing. Top off again cold, and check the reservoir too. Drive it around and monitor the temp gauge, it should sit right in the middle.
- Use proper Honda coolant mix
- Run engine with heater on to bleed
- Squeeze hoses to release air
- Check for leaks after cooling
Checking Your Work and Test Drive
Start the car cold and watch the temp gauge climb steady. It should reach normal operating temp without shooting up or staying low. Feel the heater, it should blow hot quick now. No more cold rides.
Take it for a spin, highway and city, keep an eye on the gauge. If it stays steady and no leaks under the car, you nailed it. Sometimes air pockets hide, so check coolant level over the next few days and top off.
If something feels off, like overheating, double check the thermostat orientation or bleed again. But usually, it’s smooth sailing. Pat yourself on the back, you just saved a few hundred bucks.
- Monitor gauge during warmup
- Test heater output
- Drive and watch for issues
- Recheck coolant levels later
Final Thoughts
Swapping the thermostat on your 2013 Honda Civic is a solid win that keeps the engine happy and your wallet fuller. Do it right with good parts and bleeding air properly, and you’ll avoid bigger headaches down the road. Next time the temp acts weird, you’ll know exactly what to tackle. Drive safe and enjoy that perfect heat.
| Tool/Part | Description | Why You Need It | Approximate Cost |
|---|---|---|---|
| 10mm Socket and Ratchet | Basic socket set | To remove housing bolts | $10-20 if buying |
| Pliers or Screwdriver | For hose clamps | Loosen radiator hose | Already have usually |
| Drain Pan | Large container | Catch old coolant | $10 |
| New Thermostat | OEM recommended | Replaces faulty one | $20-50 |
| Coolant | Honda Type 2, 2 gallons | Refill system properly | $20-30 |
| Rags and Gloves | Cleaning and protection | Wipe spills, avoid mess | $5 |
| Funnel | Spill-free type optional | Easy bleeding | $20-40 |
| Torque Wrench (optional) | For precise tightening | Avoid over/under torque | $30+ |
Frequently Asked Questions (FAQs)
Is it safe to change the thermostat myself on a 2013 Honda Civic?
Yeah, it’s totally doable if you take your time and follow steps. The job is straightforward without needing to remove big parts like the intake. Just work on a cold engine to avoid burns from hot coolant. Wear gloves and eye protection too. Many folks do this in their driveway and save tons on shop labor. If you’re new to wrenching, watch a quick video for visuals, but the lower hose location makes access decent.
Can I use any thermostat or does it have to be OEM?
You can go aftermarket, but OEM Honda ones last longer and open at the exact right temp. Cheap ones often stick early or fail quick, leaving you doing the job again soon. For example, get the one around 180 degrees that matches stock. It comes with the gasket usually. Spending a bit more upfront means peace of mind, especially since you’re already in there.
Do I need to drain all the coolant before starting?
No, you only drain enough to get below the thermostat housing level. Open the petcock and let out a gallon or so. This minimizes spill when pulling the housing. Save the old coolant if it’s clean and reuse for topping off, but fresh mix is better overall. Always dispose of old stuff properly at a recycle spot.
Is bleeding air important after installing the new thermostat?
Absolutely, skipping this causes hot spots and possible overheating. Run the engine with heater max hot, squeeze hoses, and top off as bubbles escape. Do it until the fan cycles and no more air burps. Some use a spill-free funnel for easier no-mess bleeding. It takes 20-30 minutes but prevents comebacks.
Can a bad thermostat cause poor gas mileage?
For sure, if stuck open the engine runs cold forever, making the computer dump extra fuel to compensate. You’ll notice worse mpg and sluggish warm-up. Once replaced, mileage bounces back quick. I’ve seen Civics gain 2-3 mpg just from this fix. Plus, the heater works great again.
Do I have to jack up the car for this job?
Not really, everything is reachable from under the hood. Draining the petcock might need you to slide under, but no jacking required. If your Civic is lowered, it might be tighter, but stock height is fine. Just good lighting helps spot the housing bolts.
Is there a special way to orient the new thermostat?
Yes, the spring side faces into the engine block, and the jiggle valve or bleed pin points straight up. Wrong way and it won’t work right or bleed air proper. Compare to the old one before pulling it. This little detail makes all the difference for smooth operation.
Can I reuse the old gasket or O-ring?
Better not, new ones seal perfect and prevent leaks. Most thermostats include a fresh one. If yours doesn’t, grab a separate gasket. Old ones harden and cause slow drips that mess up the driveway. Cheap insurance to swap it fresh.
