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Old 06-17-2009, 12:44 AM
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Default DIY low temp thermostat and fan switch


Disclaimer: The following is provided as a GUIDE ONLY, and neither myself, nor Honda Fit forums take any responsibility for the outcomes of someone else doing the following. You follow these steps at your own risk!

As you can tell this was done on a JAZZ but the information is correct for both Fit and Jazz. The USDM thermostat and housing is a little different but the parts and procedures are the same.

The most asked question is what parts will FIT. Ha the switch and thermostat come from a civic all of the switches and thermostats will interchange.


Well I finally got my SPOON low temperature thermostat, low temperature fan switch and magnetic drain bolt set for my Jazz 1.5 Vtec. So here is a DIY on installing the thermostat and fan switch relevant to the 1.5 Vtec and it looks like other Jazz engines but I am not sure at this point. The drain bolt set will have to be on another day.

Tools needed: first and a must have one 24 mm wrench or DEEP socket as normal ones won't fit because of the plastic cable connection on the fan switch (the blue part in the photo). One 10mm wrench, 10mm socket and ratchet, two extensions one short about 3-4 inches and one long 6-7 inches. I used a 1/4 inch (small) socket set as I have one but I think you could get by with a slightly larger 3/8 inch ratchet set. A set of pliers to take off hose connection clamps. One Philips head screw driver to loosen air box TB connection.

Here we have the goodies with their boxes so you can see the part numbers.

This is a bitch of a job for just changing a thermostat, well not too much of a bitch but it is time consuming just because of the position of the thermostat housing on the extreme right (looking from the front)of the engine bay and you have to lean way into the engine bay over the grill and it's literally a pain in the back.

You start by taking off the Air box and set it aside out of the way and this is what you get.

Next reach down and put a container under the radiator drain area, it doesn't have to be too large as only a little over 2 liters will come out then open the anti-freeze drain winged nut (NEVER ON A HOT ENGINE) on the bottom of the radiator on the right side looking from the front. I just turned it until it came right out but remember not to lose the small black "O" ring on it. If you want the anti-freeze to come out real fast take off or loosen the radiator cap.

You can't see all the nuts because of the large black plastic enclosed wire run under the left red arrow, and this other cable run under the right arrow.

Here you can see the pain in the butt cable run at the left arrow. The arrow on the right is pointing to a tit that you push down to get this blue clipped grey cable run out of the way, just push down and pull the blue plastic housing off the copper colored bracket and lower it out of the way.

Here is what we came for and it is the easiest part of the job "The Fan Switch" right in the center of this photo above the center red arrow. Now while the thermostat housing is still tight to the engine block is the best time to take the fan switch out.

Reach in and pinch the grey plastic connectors tit to release the connector and pull it off. Use the 24mm wrench and or DEEP socket and loosen it up it. Easy job because it's not in too tight and after breaking the set just use your fingers to screw it out watching out you don't lose the black rubber "O" ring.


The left and right arrows point to the upper and lower radiator hoses just pinch the clamps together and twist the hoses and they slide of and just move them out of the way. With the hoses off and the fan switch out of the way you can start to see the thermostat housing better.

The upper arrows are pointing to some bolts that YOU DON'T need to remove. I learned the hard way that the housing that they are holding in is NOT part of the thermostat housing even though it looks like it ( big sigh). There is one more large hose connected to the extreme rear of the housing but I left it on and there was enough play to move the housing around to take out the old thermostat and put in the new one but if you want to paint your housing it will need to come off.

Now we can get to moving that big a** bitch of a cable run. Go to the firewall side of your Throttle Body (TB) and this upper red arrow points to the water supplying hose connections to the TB. As I always leave mine off this was easy for me but you just pinch the clamps and pull off the hoses and move them out of the way making sure you don't lose the small hose clamps.

Then the black slide on wire clamp right at the point of the lower arrow can be pulled upward and backward at the same time to get this black clamp off the gold looking steel bracket. It is hard to pull as it's in the rear of the engine compartment and you are pulling against the cable run but it does just pull off no tits or anything holding it in place so just keep pulling.

Yep it really comes off and now the big plastic cable run has just enough play in it so you can get at the thermostat housing bolts.

The housing STILL has one more hose to take off and it's the lower end of the TB water connection, just pinch the clamp and slide it off again making sure you don't drop the clamp, believe me it is very easy to drop them WAY down into the engine bay just ask me. Now this hose is loose at both ends so make sure the whole hose doesn't drop down out of sight.

Now it's just a matter of running you hand around the thermostat housing and using the 10mm socket and the correct length extensions to remove all the bolts you come across. I was so busy chasing down lost clamps and bolts I forget if it is 4 or 5 bolts but you will know as the housing gets loose when ALL the bolts are out.

"Eureka" here it is off and old thermostat is OUT.

Now comes the part you have to be VERY CAREFUL about. In the photo you can see a small cut out area of the block that is covered by the thermostat housing right in the upper center of the hole with left red arrow pointing at it. Next to it are two more notched areas of the block that MUST LINE UP WITH THE BUMPS ON THE ENGINE SIDE OF THE THERMOSTAT GASKET. And make sure the part of the thermostat with the SPRING goes inside the block not sticking out.

Honda is not stupid so there is a small valve at the top of the thermostat that just happens to be right at the top so it you put this piddle valve straight up it will make the gasket be it the correct position also, pretty clever those Honda engineers, but then those same engineers designed the engine so you can't see the thermostat and put the housing back on at the same time so there must be a few dud engineers around Honda also.

Now the tricky part that would be so much easier if humans came with 3 arms.

If you stick the new thermostat into the block hole stays there without falling out (if you don't breath on it) so now ALL you have to do is sneak up on it very quietly and put the housing back on REAL REAL REAL CAREFULLY (and remember you can't SEE all of it) so you don't knock the thermostat out of alignment and then you remember you left the housing bolts on the floor of the garage and have to take the housing off and get the bolts and put one in you mouth and start all over again CAREFULLY positioning the housing back over the thermostat once again (Hint: don't forget to have the bolts somewhere at hand).

Get one bolt started on either end of the housing all the while holding pressure in on the housing so it doesn't slide around and knock the thermostat out of alignment and luckily my bolts screw in with finger pressure and then get one started in the other end and just snug them up with the socket you made sure you had close at hand. Now you can rest your fingers and straighten out your back and give it a rest. Now one by one tighten the bolts working on one end then a bolt on the other back and forth.

YEA I know there is a guy jumping up and down in the back of the room waving his hand waiting to ask "what is the torque spec?" Guess what I didn't torque them..... using the ratchet from a 1/4" set that is only 3 inches long it would be pretty impossible to over torque these 10mm bolts so I just tightened them "mechanic" tight.

And guess what if you look at the photo you can see on the left part some grayish white goop around some water passages that I guess is some kind of silicone sealer. I didn't change that either. The car only has 4000km and it wasn't leaking so I just left the old sealant in place.

If you have loads of kms or just feel you need to go ahead and scrape of the old stuff and run a bead of new silicone around the same areas wait for it to set up and then put the housing back on.

Here is the thermostat with the piddle valve near the top at the end of the red arrow just make sure this is at the top of the hole and you should be ok. The valve is there to allow any trapped air or steam to escape past the thermostat before it opens.

Last edited by claymore; 10-17-2012 at 07:35 AM.
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Old 06-17-2009, 12:44 AM
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Default Low temp part II

Here is the final result. After a hard trash run which would usually stock run the temperature up to 210 here is a photo of the gauge now at about 185-190 and it never gets hotter. When running normally and not stopping before the thermostat change it would run at 180 now with low temperature thermostat and fan switch it runs at 160.

Was it all worth it? I think so but it is the most expensive thermostat I have ever purchased. I would give the price but do not want any trouble from trader so PM me.

The result of this installation is an average drop in temp of 20 degrees normal and 20 degrees when pushed. The fans do seem to come on more often but run for lesser amounts of time, this is because of the thermal efficiency of the radiator is enough to dissipate the lower temp faster than the usual higher temps.

Would I do it again? In a heartbeat!! I did not do this because I was having problems with my Jazz it ran fine, but for someone that wants the last ounce of performance out of their vehicle lower temps give you better performance. Am I loosing a minute amount of fuel economy due to the lower temp? Sure but I don't care about that.

Am I causing an increase in exhaust emissions? Probably a small amount but then I make up for that by keeping my vehicle in top tune replacing my plugs and cleaning my air filter every 5000km much better than some of these old clunkers that are never tuned.

That's it I hope you enjoyed reading this and don't be afraid to reply with questions I will try to answer them, and now everybody knows where their fan switch is!
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Old 10-17-2012, 05:52 AM
Oahu Oahu is offline
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I am getting ready to change the water pump and decided to do the termostat and switch. Can you give me the part numbers for the spoon parts you installed on your fit?


Btw: thanks for the valves DIY - I completed!
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Old 10-17-2012, 07:35 AM
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claymore claymore is online now
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Sorry no longer have them but I used the ones listed for a Civic
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