How To:Thermostat

[mach69]

How to replace your thermostat.

Difficulty: 3/10 (Easy, just a PITA)

Disclaimer: The steps below are how I replaced my thermostat. If you follow these steps to change your thermostat, you do so at your own risk. If you hurt yourself or your car, I am NOT responsible. By following these steps, you agree to this disclaimer. Got questions? Ask away I’ll do my best to answer them. Most important: BE SAFE!

Tools Needed: Socket Wrench, 8mm socket, 10mm socket, 12mm socket, 8mm wrench, 12mm wrench, 14 mm wrench, Pliers, Various extensions (3”, 6”, U-joint), drain pan.

I used the pic below to help me out A LOT!



1. Remove battery cover and negative battery terminal.

2. I then jacked the car up. Please be safe and use wheel chocks. Also, never go under a car that is using just a scissors jack to hold it up.

3. Remove under tray/splash shield.
*Note: If you can’t get past this step, bring your car in to have a professional do this work.

4. Remove the coolant overflow tank cap. CAUTION: Do not do this when the car is hot. The coolant system is under pressure and will blow up in your face.

5. Drain your engine coolant. Loosen up the radiator drain plug with a screwdriver. The drain plug is located on the back bottom driver side of the radiator. I had to use a pair of pliers to pull it out after I un-screwed it. The coolant will fly out, be ready with a drain pan. Once it’s done draining, reinstall the drain plug.
Pic 1


6. Loosen the Serpentine Belt around the power steering pump. In order to do this you must take the serpentine belt off the tensioner using a 14 mm wrench. Go clockwise to take tension off the belt.
Pic 2


7. To get to the top left thermostat housing bolt, I moved my power steering pump out of the way. To do this, all the bolts must come off. There are three 12mm bolts. However, due to the power steering line connection to the power steering pump, the top left bolt will stay with the pump. The 3rd bolt isn’t visible in the picture, but it is located underneath the pump, directly below the bolt on the left (the bolt that won’t come out completely.) The wiring harness line to the pump will also need to be removed. To remove the electrical connector from the power steering pump you need to compress the clip to get it to release.
Pic 5


8. Remove the three 8mm bolts on the thermostat housing. I ended up putting the power steering pump almost above the intercooler. This gave me LOTS of space to work on the thermostat. I removed the top 2 bolts from the top and the bottom bolt from below the car.
Pic 3, Pic 4, Pic 9




9. Remove the 2 hoses from the thermostat housing. Due to the heat of the engine the hoses were stuck on my thermostat housing. I loosely bolted the housing back to the block to gain leverage in order to remove the hoses. With the new found room, I pulled the housing back and up. This gave me ample leverage to pull the hose clamps and hoses off the thermostat housing. Take out the old thermostat.
Pic 6


New (left) vs Old (right)
Pic 7


Thermostat opening
Pic 8


10. Put the 2 hoses on the new thermostat housing.

11. Re-install the three bolts that hold the thermostat in place.

12. Add coolant into the reservoir tank. There is no radiator cap, so all the coolant will go through the tank. Check for leaks. I put in some water wetter.

13. Reinstall the power steering pump. 3x 12mm bolt.

14. Put the serpentine belt back on. 14mm tensioner bolt.

15. Check for any leftover tools and double check everything. Reinstall the negative battery terminal. Start the car up and let it warm up. Constantly check for leaks when the car is running. You can double check your thermostat by touching both radiator hoses. You know that annoying hose that you took off to replace the thermostat? Once that hose heats up, you know your thermostat is working properly.

If there are any corrections I need to make, please comment so I can change it.

[qwerty4550]

Does the gasket come with the new thermostat? How much was the thermostat? Thanks for the write-up!

[Scribbles]

Originally Posted by qwerty4550 Does the gasket come with the new thermostat? How much was the thermostat? Thanks for the write-up!

When I did mine, the gasket came with it and the unit was around $70 from the stealership.

[redmnsterut]

Gasket should come with it from the dealership. I got min for 55 at the dealership.

Good wright up. I managed to get mine off and re-install the new with out taking the power-steering pump off. It can be done with out taking it off but can see from the pics that it makes it a lot easier with it moved.

[mach69]

I bought mine for $42 and shipping.

Thermostat

The gasket came with the thermostat.

[Raider]

Just saw this! @mach69 got $500,000 msf bucks.

[daztdMS6]

Thanks for the write-up Mach69. I'll be replacing the thermostat on my car soon. I just got the parts yesterday.

[mach69]

Originally Posted by Raider Just saw this! @mach69 got $500,000 msf bucks.

Thank you.

Originally Posted by daztdMS6 Thanks for the write-up Mach69. I'll be replacing the thermostat on my car soon. I just got the parts yesterday.

Best of luck. How did it go?

[Vansquish]

Originally Posted by mach69 How to replace your thermostat. Difficulty: 3/10 (Easy, just a PITA) If there are any corrections I need to make, please comment so I can change it.

Holy unnecessary steps Batman! (well...maybe...)

I recently had to do my thermostat on my MS6, and while the engine is the same, the space in the engine bay may not allow the same contortions that I was able to perform.

I removed/replaced my thermostat w/out touching anything but the undertray, the radiator drain plug and coolant reservoir cap and the thermostat and the hoses/clamps that were connected to it.

1. Remove battery cover and negative battery terminal.

2. I then jacked the car up. Please be safe and use wheel chocks. Also, never go under a car that is using just a scissors jack to hold it up.

3. Remove under tray/splash shield.
*Note: If you can’t get past this step, bring your car in to have a professional do this work.

4. Remove the coolant overflow tank cap. CAUTION: Do not do this when the car is hot. The coolant system is under pressure and will blow up in your face.

5. Drain your engine coolant. Loosen up the radiator drain plug with a screwdriver. The drain plug is located on the back bottom driver side of the radiator. I had to use a pair of pliers to pull it out after I un-screwed it. The coolant will fly out, be ready with a drain pan. Once it’s done draining, reinstall the drain plug.
Pic 1

6. Locate the thermostat (use a flashlight, you'll need it)

7. Using long-handled pliers, unclamp the smaller of the two hoses where it attaches to the thermostat. Then pull that hose free of the thermostat.

8. Using a small ratchet, extensions, and 8mm socket, remove the three 8mm bolts on the thermostat housing.

9. Get underneath the car, and locate the larger hose that runs out from the thermostat and down to the bottom of the radiator. Unclamp this hose and pull it free.

10. At this point, you should be able to pull the thermostat off the block, and feed it up and out (or down and out) of the engine-bay.

11. Now that the thermostat and large hose are free, you will have plenty of room and leverage to remove the larger hose from the thermostat
(keep in mind, I did my thermostat after 85k, and the large hose was pretty well stuck).

12. Put the larger hose on the NEW thermostat housing

13. Feed the hose back into the engine bay and seat the thermostat. Screw the 8mm bolts back in.

14. Add coolant into the reservoir tank. There is no radiator cap, so all the coolant will go through the tank. Check for leaks. I put in some water wetter.

15. Check for any leftover tools and double check everything. Reinstall the negative battery terminal. Start the car up and let it warm up. Constantly check for leaks when the car is running. You can double check your thermostat by touching both radiator hoses. You know that annoying hose that you took off to replace the thermostat? Once that hose heats up, you know your thermostat is working properly.

If there are any corrections I need to make, please comment so I can change it.
2.

[daztdMS6]

Originally Posted by mach69 Best of luck. How did it go?

I haven't done it yet.....maybe in a couple of weeks

[BobbleHead]

ugh P0126 and coolant temps down to 157 on the highway. Looks like i gotta do this. Thanks for the writeup

[mach69]

Originally Posted by Vansquish 7. Using long-handled pliers, unclamp the smaller of the two hoses where it attaches to the thermostat. Then pull that hose free of the thermostat. 8. Using a small ratchet, extensions, and 8mm socket, remove the three 8mm bolts on the thermostat housing. 9. Get underneath the car, and locate the larger hose that runs out from the thermostat and down to the bottom of the radiator. Unclamp this hose and pull it free.

You have enough space to remove the thermostat bolts from the top? Maybe I did as well, but not with my huge, clumsy hands.

[Vansquish]

I wouldn't exactly say that it was "the top", but yes...I snaked my hands in there and was able to get them out.

[redmnsterut]

When i did mine, i still had the spring clamps on it and with out moving the PS pump or intake manifold, the clamps were bitch to get to with pliers.

Should only take 1hr or so if that.

[ak_spray]

I'm going to do this next month when I do my injector seals, PVC valve, Valve Cover Gasket amongst others. Thanks for the write up.

[Big_Burd]

Thanks for the write up! Saved my butt, I did it without moving the power steering, but I really wish I did. Would've probably saved some time.

[I<3Groceries]

Originally Posted by redmnsterut When i did mine, i still had the spring clamps on it and with out moving the PS pump or intake manifold, the clamps were bitch to get to with pliers. Should only take 1hr or so if that.

Same here. Not removing the PS pump wasn't even an option. The stupid tension clamps on the hoses liked to whoop my ass anyway. I pinched the ever loving fuck out of my finger with pliers. Lol!
But it is all very easy anyway.
PS bolts kinda pissed me off. But still pretty low on the difficulty scale. I went ahead and flushed my cooling system at the same time.
New operating temp is around 190, compared to 180ish with the older style tstat.

Sent from my Galaxy Nexus using Tapatalk 2

[jvella22]

After replacing the thermo did any of you have trouble with the "Amb" temp display? Mine seems to not be reading anything.

[evidence]

Originally Posted by jvella22 After replacing the thermo did any of you have trouble with the "Amb" temp display? Mine seems to not be reading anything.

I believe that's the cylinder that snaps into the holder in front of the radiator? Was it knocked down or disconnected while you replaced the thermo? They are isolated functions.

I also just ended up removing the PS pump, it takes all of 10 minutes and gives you so much room to work with. The clamps can be a bitch so you'll likely spend more time than that finagling them with the PS pump on. Getting the serpentine belt back on was a bit annoying, but if you reach from behind the lower control arm you can get much better leverage on the tensioner

[Spectrum24x]

Going to do this today, just one question... Autozone has 2 models. One has a short angled hose connector and the other has a long straight hose connector. From your pics you have the short angled one I'm guessing mine would be the same? 2007 Speed3

http://www.autozone.com/autozone/par.../N-jpzc5Z9pd73

[Spectrum24x]

Man, you guys are all sugar coating this and making it sound too easy. Let me preface this by saying I am mechanically inclined however this is the first diy I've done on the speed3 that really involves taking anything apart. Doing this thermostat is making me miss my rx7, everything was so easy to get to.

I will admit once I got the right tools (appropriate size extensions and box wrenches)!the job became a bit easier but man, could that thermostat be in any worse spot?

I went the route of taking the power steering pump off buy only after an hour of trying to get the top left bolt off the thermostat without removing the power steering pump. Once I got the pump off the thermostat was easy to remove however removing the power steering pump itself was a pain... That lower bolt was one I needed an appropriate size extension for and it was still a nightmare.

I'll admit I spent about an hour trying to get the serpent (devil) belt off bc i loosened the tensioner belt instead of turning clockwise as stated in the op but once I went back and re read that I got the belt off pretty easy.

So 5 hours later I'm soaked in coolant and power steering fluid but I've got it all back together except I've got to do some reading on the best way to replace the devil belt and ill be doing a coolant system flush and filling it with coolant tomorrow. If this doesn't resolve my Low coolant temp for stable operation CEL then I'm really going to be ticked.

At any rate thanks for the great write up it has been helpful I guess I'm just frustrated bc this is the first car I've worked on that's newer than a 1991 which is challenging me to grow my mechanical skills as well as my set of tools

[MikeDaddy32]

Hi Guys!

New to the forum, but I used some of the comments on here to help with the job. Thanks everyone!

First off the issue with my car, 2008 Mazda 3, was after about 15 minutes of running the temperature gauge would be all the way hot and not come back down. Rather then take it to the mechanic, I wanted to attempt the thermostat myself and hope that was the problem.

I was able to do it without taking off anything other then the thermostat. A 4 inch extension on the socket wrench can reach all 3 bolts. It was especially helpful to have another person underneath the car guiding the wrench in place, then cranking the bolts off from the top.

The hardest part I found was loosing the hose clamps enough to take the hoses off. A lot of pliers and wiggling to get that clamp off! Once the larger hose was off, we found it easier to remove the bolts on the thermostat and drop the unit down beneath the car, it will come down and hang right beneath the fender. Then take the smaller hose off and put it straight on the new thermostat. Then raise the thermostat back up in place and put in the screws. Now it's back to the big hose which was equally as difficult to put back on. In the end we had a pliers holding the clamp closed from above, then another person beneath the car with pliers helping to push the clamp in place.

About a hour and a half total for the job and it fixed the my heat problem!

One more note: almost exactly 1 gallon of coolant fluid drained, so plan accordingly.

$30.99 Thermostat
$25 for one gallon of coolant fulid from Mazda (non mixed)
$10 various pans and distilled water

[warlockfan92]

UPDATE: did mine a few days ago, not too bad of an install as i had a wealth of tools at my disposal. changed the belt while i was at it, all in all it took about 2 hrs to get everything done

[Dingo]

Excellent write up, thank you! I changed the thermostat, temperature sensor, coolant, and oil today. My car's idle has smoothed out and it's running much better now (and the P0126 code is now gone).

[Raider]

Fuck My Life. I go a CEL last week. Figured with cold and many cranks to start, it was egr. Well, fixed a dashhawk for a local, and thought I would clear it. Then I saw the code. Fuck. My hands are too fat, I'm prolly taking the manifold off and will be doing this and cleaning about 80,000 miles of tar from the valves. Fuck.

Yay for how-to.

[tddvrrn]

Originally Posted by Raider Fuck My Life. I go a CEL last week. Figured with cold and many cranks to start, it was egr. Well, fixed a dashhawk for a local, and thought I would clear it. Then I saw the code. Fuck. My hands are too fat, I'm prolly taking the manifold off and will be doing this and cleaning about 80,000 miles of tar from the valves. Fuck. Yay for how-to.

i always look forward to your posts. they are like a ray of sunshine and positivity.

stay sweet raider.

[Raider]

Originally Posted by tddvrrn i always look forward to your posts. they are like a ray of sunshine and positivity. stay sweet raider.

LOL! I knew I was a super-positive person. Thanks for proving my point. That said, better mood now, I got a buddy who is a hardcore mechanic. Gonna totally help me, so I don't fuck shit up. The valve cleaning is gonna the toughest part, but well worth it.

[tddvrrn]

Originally Posted by Raider LOL! I knew I was a super-positive person. Thanks for proving my point. That said, better mood now, I got a buddy who is a hardcore mechanic. Gonna totally help me, so I don't fuck shit up. The valve cleaning is gonna the toughest part, but well worth it.

this is the first car i've really wrenched on, and i was able to do my valves and clean my egr by myself. it wasn't bad, just time consuming. having a friend will make it a walk in the sunshine

but fuck yes, is it ever worth it. i did mine around 70k and it made the engine feel new. it is completely worth your time.

[Raider]

I have wrenched for 25 years, it is not new. I am just pissed about having to do it. I did the EGR how-to, was not hard. Changing plugs on a 5.0 1985 Thunderbird was not fun.

[Coma9]

Hey, so you guys all needed a new Thermostat housing to go with the Thermostat and gasket? The mechanic I took my car to said it was going to go around $200 just to do the Thermostat, because it needed to come with a new housing as well... that's with my %15 friend discount...

[mach69]

Originally Posted by Coma9 Hey, so you guys all needed a new Thermostat housing to go with the Thermostat and gasket? The mechanic I took my car to said it was going to go around $200 just to do the Thermostat, because it needed to come with a new housing as well... that's with my %15 friend discount...

Originally Posted by mach69 I bought mine for $42 and shipping. Thermostat The gasket came with the thermostat.

In the link above the thermostat comes as a whole unit with the housing. I honestly didn't even try to separate them. Not sure if you can? Its easy to do with basic tools, save yourself the $150.

[alien_sporez]

Somewhat related question: what temperature is the radiator fan supposed to kick on. My coolant temperature while idling is going over 200F and the fan isn't kicking on. No fuses are blown. I just replaced my driver's-side coolant hose so that it routes away from my FMIC cold pipe. Anyone know what the temperature for the fan to start is (I have GenPu if it matters)

[Big_Burd]

Originally Posted by Coma9 Hey, so you guys all needed a new Thermostat housing to go with the Thermostat and gasket? The mechanic I took my car to said it was going to go around $200 just to do the Thermostat, because it needed to come with a new housing as well... that's with my %15 friend discount...

I'm not sure, 200$ is really high, go to autozone tell them you need a thermostat for a MS3/6 it will be about 40$ (idk what you mean by housing) its one part that sticks in there,and shouldn't take you more than 3 hours to do absolute tops, if you're shitty at wrenching, if you're good at mechanics and can be done in around 1 hr.

I wouldn't pay more than 150$ to have it done, including the cost of the part. It's reasonably simple, drain coolant, pop of the 2 hoses, 3 screws that hold the thing in place and there ya go! It is in the biggest bitch of a place to get to which is what made it extremely difficult for me, I also didn't move the PS pump or any of that..would've saved time but I didn't want to fuck with it.

[Raider]

I ordered my thermostat Wedneday received Friday from Onlinemazdaparts.com. Was like $58 shipped. It is in the housing, and comes with the gasket on it. Mazda quotes 1.5 hours. If you loosen the serpentine belt, remove the power steering pump. it is all right there easy to get to. Took off the intake mani at the same time to clean the valves, but was done with thermostat in about 30 minutes.

[memin]

Originally Posted by Spectrum24x Man, you guys are all sugar coating this and making it sound too easy. Let me preface this by saying I am mechanically inclined however this is the first diy I've done on the speed3 that really involves taking anything apart. Doing this thermostat is making me miss my rx7, everything was so easy to get to. I will admit once I got the right tools (appropriate size extensions and box wrenches)!the job became a bit easier but man, could that thermostat be in any worse spot? I went the route of taking the power steering pump off buy only after an hour of trying to get the top left bolt off the thermostat without removing the power steering pump. Once I got the pump off the thermostat was easy to remove however removing the power steering pump itself was a pain... That lower bolt was one I needed an appropriate size extension for and it was still a nightmare. I'll admit I spent about an hour trying to get the serpent (devil) belt off bc i loosened the tensioner belt instead of turning clockwise as stated in the op but once I went back and re read that I got the belt off pretty easy. So 5 hours later I'm soaked in coolant and power steering fluid but I've got it all back together except I've got to do some reading on the best way to replace the devil belt and ill be doing a coolant system flush and filling it with coolant tomorrow. If this doesn't resolve my Low coolant temp for stable operation CEL then I'm really going to be ticked. At any rate thanks for the great write up it has been helpful I guess I'm just frustrated bc this is the first car I've worked on that's newer than a 1991 which is challenging me to grow my mechanical skills as well as my set of tools

Hell yeaaa they are sugarcoating this shit, difficulty level 3 MY ASS!!!!!This is at least 5 bro(installing a TIP is a 3). Especially reaching the clamps and no room to do shit(I did not remove power steering or IM).If your planning on doing this make sure you clear at least 4 hrs of your schedule because this job is not a punk i did it by myself. I hope I don`t have to do this again.

[skeeter149]

thanks everyone for the feed back. i gotta do this tomorrow, i have been hearing my fans way too much lately and coolant temps are at like 235... ouch. gonna get the tstat at o'rielly for 26.99 and knock it out tomorrow. this write up is super useful and i will be moving the power steering pump for ease. my car is at 31,7xx miles and is a 08 speed 3. thank you again all

[skeeter149]

job done. took me some extra time but after i ran to the store and got some 1/4" extensions to get the power steering pump off, we were cooking with gasoline. thank you all posters and especially op cause i wouldnt of thought taking the pump off would be that easy. new coolant temps after idling 15 mins and revving to 2k for 1 min= 181*. thank god, my fans didnt turn on for the first time in who knows lol.

[BobTeatow]

Cleared P0126 but in test drive this morning in freezing CT, OBD/ELM/Torque shows temperature never going above 160F.

So what are the risks of delaying thermo replacement?

I'm not noticing any problems, engine running okay and cabin heat okay.

Thanks,
Bob T

Mazda 3 / hatchback with 2.x engine, no-turbo.

[Raider]

Just replace the damn thing. You have the how-to. Too lazy? Then take it to a shop.

[BobTeatow]

Right, I will, but its a matter of money/time and priorities.