I recently replaced thermostats on 2 Rav's (my and my sister's). They both had the original thermostats: one was 15 years old with 167K miles, and the other was 14.5 years old with 155K miles. Luckily, in our cases, both thermostats were broken in the OPEN position, so we just had no cab heat. If you are nearing this mileage or beyond it, you might anticipate a thermostat failure.
Note: This is an easy DIY with one small caveat...its best with small hands!! I'm a woman, and I have small hands, and it was still a little tricky getting the nuts which hold the hose on placed back on after removing them and replacing the thermostat. If you have big hands, I'd suggest you enlist someone with small hands, or slip a magnet under your glove into a finger tip to reduce the chances that you'll drop those little nuts while you're trying to get them back on, because they won't fall onto the floor, so you'll be searching for them.
DIAGNOSTICS:
You might have a broken/failing thermostat if:
a.) You're overheating--it might be broken and stuck in the CLOSED position; in this case, the coolant cannot cycle through the radiator, so you're temp gauge spikes, and you risk overheating the engine.
OR, conversely,
b.) You're not getting any heat--it might be broken and stuck in the OPEN position; in this case, the coolant is constantly cycling through the whole system, so you're never reaching operating temps, and your heater is blowing cold air on you. (The #2 case is better because while it's not fun to have no interior heat in -5F temperatures, at least your engine is not overheating. I ran for a couple of weeks with cardboard in front of the AC condensor, which is helpful in getting the temp up a little, but if you do this, just don't block the transmission fluid cooler side (LHS on USA models).
Or
c.) You're hit-or-miss with the cab heat--sometimes it works, sometimes it doesn't. You could have a thermostat that's not totally busted yet, but is off axis, or closing at too low of a temperature.
REPLACING THE THERMOSTAT:
To replace the thermostat, you need these tools and supplies:
- new thermostat & gasket (Toyota part #'s are 90916-03090 (thermostat) & 16325-63011 (gasket), or good aftermarket versions).
- coolant or distilled water (in case you spill some coolant)
- clean 1 gallon container (to hold drained coolant)
- straw or tubing (not totally needed, but it makes it cleaner)
- large plastic bag (to catch coolant when you remove the hose)
- small plastic bag and rubber band (to cover oil filter housing)
- oil filter wrench attachment (I use the Fram attachment)
- ratchet wrench with extension (to remove oil filter)
- 10 mm box-end or closed end wrench/spanner (also nice if you have a very small 10mm ratchet, or an open-end ratchet too)
- Lisle No-Spill funnel (for bleeding the system)
STEPS:
-see the "Final Notes" at the end of this post for other jobs you can do while you're at this one
1.) Find the radiator drain plug/spout. This plug is a white plastic knob left-of-center on the bottom of the radiator. (You might have to remove the plastic splash guards, so if you have a grille guard/bull bar like me, you might have to remove that, too.) Place a straw or tubing over the spout, and run the tubing into a clean container that will not contaminate your coolant (if you're planning to reuse it). Picture:
2.) Open the plug by turning it counter-clockwise, as usual. Do not remove the plug unless you want coolant coming out in a less-controlled fashion. The stream is fairly weak, so it takes several minutes for the coolant to drain. If your system is bled and full, you should get close 1 gallon from the drain. After it is fully drained, remove the plug and inspect it--there should be a little gasket at the base, and it should be clean.
3.) Replace the plug and close it tightly, by hand. (No picture)
4.) Remove the oil filter:
5.) Place a bag secured with a rubber band over the area where the oil filter was, to prevent dirt, coolant, or nuts (!) from accidentally falling through. Find wrenches that will fit for the area.
6.) Place a plastic bag under the hose which is located to the right of the oil filter--this is where the thermostat is, and this is what you'll be disconnecting. When you disconnect it, you'll have some coolant leak out. You want to catch it with the bag so it doesn't make a mess.
7.) Using the whatever 10mm wrench that fits, remove the nuts securing the hose. (No picture, see the pics above)
8.) Remove the hose--you'll either see your thermostat sitting on the housing (like this below), or in the hose--which ever it happens to be most firmly placed within. Note the orientation. If your thermostat is in the housing and you can't remove it by hand, just slightly wedge a flat-head screwdriver under the rim/gasket and it will pop out.
9.) Inspect the thermostat to see if its obviously broken. If you can hold the thermostat is your hand, it will be cool, and it should be closed. If you see any opening between the metal rim and the rubber, then you know its broken (open). But, it could still be malfunctioning even if its not as obvious as this. One of the thermostats I removed was wide open, and I could see right thought it. Also, the center shaft was off-axis. I didn't even have to test it because it was obvious by these signs.
On the other thermostat, it wasn't obvious at first. I poured water on the top, and it drained through, so I knew it wasn't totally sealing. When a thermostat is working properly, water should not pass through it when its cold. I needed to test the replacement thermostats anyway, so I put the old one in as well, and tested them by heating them up slowly in distilled water till reaching 82C. The thermostats should open only at this point--the new ones did, but the old one opened well before this (and was partially open to begin with). The new thermostats promptly closed when I let the temp of the water fall, but the old one didn't close once open. So it was broken indeed. Picture, testing thermostats in the kitchen (which is why I had to get this done before the Thanksgiving cookin' started!):
10.) Back to the car, put a new gasket on the new thermostat. As far as I could tell, the gasket is symmetrical, so no worries about putting it on backwards. Picture:
11.) Replace the thermostat by lining up the jiggle valve with the "protrusion" on the hose and putting back as you found it. The jiggle valve is a little metal piece pierced through the rim of the thermostat. According to the Toyota Service Manual, align this jiggle valve within +/- 5 degrees of the protrusion on the hose. Then put the hose back onto the bolts, being careful not to dislodge or move the thermostat.
12.) Replace the two nuts and tighten them down. The torque spec is 8.8 N-m/90kgf-cm/78 in-lbf, but good luck getting a torque wrench in there! I didn't need much force to remove them, so I just "torqued" them back to something that felt about like what'd I'd felt in removing it and checked it later for leaks.
13.) Replace the oil filter. Rub a thin layer of oil around the base. The proper tightening on this is by hand till you have it on good, then 3/4 turn with the wrench.
14.) Refill the radiator with coolant. If you caught the coolant that leaked from the hose when you removed it, and you know your system was fully bled and full in the first place, then just add it to what you drained from the radiator. If you weren't able to catch it, then I'll just say that in my case it was only about 1/3 c or so, so it should be about that. Refill the system with the coolant that you drained--if you have a Lisle funnel, attach it at this point, and pour the coolant into the radiator through the funnel. You'll notice that you're not going to be able to get all the coolant that you drained back in, because by opening up that hose, some big air bubbles got locked into the system, so you must now fully bleed the system.
15.) Bleed the system. This is an important step, and this is where the Lisle No Spill funnel is so great! TOTALLY worth the $25, you'll use it often! Pour whatever you drained into the funnel. Double-check to make sure that you haven't forgotten anything (oil filter on tight, hose bolts on tight, no tools anywhere that's dangerous) because you'll now start the engine. In the car, push the temperature control lever all the way over to hot, but don't turn the fan on. Start the engine and starting bleeding. You'll see lots of lots of bubbles, like this.
16.) Continue running the engine--you need to get the thermostat to open, so you'll need to reach operating temp. You can hold the rpms up in the 2000-2500 rpm range. Check the funnel periodically to see that there's still coolant in it--make certain there's coolant in it while the engine is running. It took me about 20 minutes to bleed the system in cold wintertime outside air; once you have the radiator fans kicking on and off for a few cycles, you'll know that everything is open and coolant is running through the whole system. Protect your hand from heat and lightly squeeze the upper radiator hose to gauge the bleed (as you get closer to having it done, there will be fewer and fewer bubbles caused by squeezing that hose). You're done bleeding when the bubbles are done surfacing. Turn off the car. You'll notice that you'll still have coolant in the funnel, but that's fine--just cover the funnel. When I was done bleeding it, before it cooled all the way, it looked like this:
As the engine cools, it will draw that coolant back in. After about 1 hour, you'll see this:
That's the coolant all back in, where it belongs. The coolant level should be up to the "throat" of the radiator filling "neck", so that when you open the cap, you can just see it.
And you're done! Replace the radiator cap and check your reservoir level. Clear the engine of tools and Mountain Dew cans, and enjoy the fact that you know have HEAT the next time it snows!!
[Final Notes: You can use this opportunity to do an oil change and coolant change while you're at it, but this DIY just shows the steps for drain-and-refill.
For my sister's '99, the coolant was horrible and hadn't been changed since who-knows-when, so I did a full coolant change on that one. For my '00, I'd just changed the coolant a few months ago, so the coolant was fine, therefore I just drained it and refilled with the same coolant. Again if you do this, be sure your system is fully bled and full before you start, and then you'll know to just put back in what you took out. Also, since you're going to remove the oil filter, you might want to just change that and the oil if you feel like it. If you want to do that, then add a 9/16th wrench to the list and a drain plug gasket (I think its M12?), and drain the oil pan first, then close it & refill the engine with oil--you don't want to forget that part later and start the engine with no oil! If you don't want to do an oil change, just do this after the car has sit a while/overnight, and you won't lose any oil when you remove the filter.]
Note: This is an easy DIY with one small caveat...its best with small hands!! I'm a woman, and I have small hands, and it was still a little tricky getting the nuts which hold the hose on placed back on after removing them and replacing the thermostat. If you have big hands, I'd suggest you enlist someone with small hands, or slip a magnet under your glove into a finger tip to reduce the chances that you'll drop those little nuts while you're trying to get them back on, because they won't fall onto the floor, so you'll be searching for them.
DIAGNOSTICS:
You might have a broken/failing thermostat if:
a.) You're overheating--it might be broken and stuck in the CLOSED position; in this case, the coolant cannot cycle through the radiator, so you're temp gauge spikes, and you risk overheating the engine.
OR, conversely,
b.) You're not getting any heat--it might be broken and stuck in the OPEN position; in this case, the coolant is constantly cycling through the whole system, so you're never reaching operating temps, and your heater is blowing cold air on you. (The #2 case is better because while it's not fun to have no interior heat in -5F temperatures, at least your engine is not overheating. I ran for a couple of weeks with cardboard in front of the AC condensor, which is helpful in getting the temp up a little, but if you do this, just don't block the transmission fluid cooler side (LHS on USA models).
Or
c.) You're hit-or-miss with the cab heat--sometimes it works, sometimes it doesn't. You could have a thermostat that's not totally busted yet, but is off axis, or closing at too low of a temperature.
REPLACING THE THERMOSTAT:
To replace the thermostat, you need these tools and supplies:
- new thermostat & gasket (Toyota part #'s are 90916-03090 (thermostat) & 16325-63011 (gasket), or good aftermarket versions).
- coolant or distilled water (in case you spill some coolant)
- clean 1 gallon container (to hold drained coolant)
- straw or tubing (not totally needed, but it makes it cleaner)
- large plastic bag (to catch coolant when you remove the hose)
- small plastic bag and rubber band (to cover oil filter housing)
- oil filter wrench attachment (I use the Fram attachment)
- ratchet wrench with extension (to remove oil filter)
- 10 mm box-end or closed end wrench/spanner (also nice if you have a very small 10mm ratchet, or an open-end ratchet too)
- Lisle No-Spill funnel (for bleeding the system)
STEPS:
-see the "Final Notes" at the end of this post for other jobs you can do while you're at this one
1.) Find the radiator drain plug/spout. This plug is a white plastic knob left-of-center on the bottom of the radiator. (You might have to remove the plastic splash guards, so if you have a grille guard/bull bar like me, you might have to remove that, too.) Place a straw or tubing over the spout, and run the tubing into a clean container that will not contaminate your coolant (if you're planning to reuse it). Picture:
2.) Open the plug by turning it counter-clockwise, as usual. Do not remove the plug unless you want coolant coming out in a less-controlled fashion. The stream is fairly weak, so it takes several minutes for the coolant to drain. If your system is bled and full, you should get close 1 gallon from the drain. After it is fully drained, remove the plug and inspect it--there should be a little gasket at the base, and it should be clean.
3.) Replace the plug and close it tightly, by hand. (No picture)
4.) Remove the oil filter:
5.) Place a bag secured with a rubber band over the area where the oil filter was, to prevent dirt, coolant, or nuts (!) from accidentally falling through. Find wrenches that will fit for the area.
6.) Place a plastic bag under the hose which is located to the right of the oil filter--this is where the thermostat is, and this is what you'll be disconnecting. When you disconnect it, you'll have some coolant leak out. You want to catch it with the bag so it doesn't make a mess.
7.) Using the whatever 10mm wrench that fits, remove the nuts securing the hose. (No picture, see the pics above)
8.) Remove the hose--you'll either see your thermostat sitting on the housing (like this below), or in the hose--which ever it happens to be most firmly placed within. Note the orientation. If your thermostat is in the housing and you can't remove it by hand, just slightly wedge a flat-head screwdriver under the rim/gasket and it will pop out.
9.) Inspect the thermostat to see if its obviously broken. If you can hold the thermostat is your hand, it will be cool, and it should be closed. If you see any opening between the metal rim and the rubber, then you know its broken (open). But, it could still be malfunctioning even if its not as obvious as this. One of the thermostats I removed was wide open, and I could see right thought it. Also, the center shaft was off-axis. I didn't even have to test it because it was obvious by these signs.
On the other thermostat, it wasn't obvious at first. I poured water on the top, and it drained through, so I knew it wasn't totally sealing. When a thermostat is working properly, water should not pass through it when its cold. I needed to test the replacement thermostats anyway, so I put the old one in as well, and tested them by heating them up slowly in distilled water till reaching 82C. The thermostats should open only at this point--the new ones did, but the old one opened well before this (and was partially open to begin with). The new thermostats promptly closed when I let the temp of the water fall, but the old one didn't close once open. So it was broken indeed. Picture, testing thermostats in the kitchen (which is why I had to get this done before the Thanksgiving cookin' started!):
10.) Back to the car, put a new gasket on the new thermostat. As far as I could tell, the gasket is symmetrical, so no worries about putting it on backwards. Picture:
11.) Replace the thermostat by lining up the jiggle valve with the "protrusion" on the hose and putting back as you found it. The jiggle valve is a little metal piece pierced through the rim of the thermostat. According to the Toyota Service Manual, align this jiggle valve within +/- 5 degrees of the protrusion on the hose. Then put the hose back onto the bolts, being careful not to dislodge or move the thermostat.
12.) Replace the two nuts and tighten them down. The torque spec is 8.8 N-m/90kgf-cm/78 in-lbf, but good luck getting a torque wrench in there! I didn't need much force to remove them, so I just "torqued" them back to something that felt about like what'd I'd felt in removing it and checked it later for leaks.
13.) Replace the oil filter. Rub a thin layer of oil around the base. The proper tightening on this is by hand till you have it on good, then 3/4 turn with the wrench.
14.) Refill the radiator with coolant. If you caught the coolant that leaked from the hose when you removed it, and you know your system was fully bled and full in the first place, then just add it to what you drained from the radiator. If you weren't able to catch it, then I'll just say that in my case it was only about 1/3 c or so, so it should be about that. Refill the system with the coolant that you drained--if you have a Lisle funnel, attach it at this point, and pour the coolant into the radiator through the funnel. You'll notice that you're not going to be able to get all the coolant that you drained back in, because by opening up that hose, some big air bubbles got locked into the system, so you must now fully bleed the system.
15.) Bleed the system. This is an important step, and this is where the Lisle No Spill funnel is so great! TOTALLY worth the $25, you'll use it often! Pour whatever you drained into the funnel. Double-check to make sure that you haven't forgotten anything (oil filter on tight, hose bolts on tight, no tools anywhere that's dangerous) because you'll now start the engine. In the car, push the temperature control lever all the way over to hot, but don't turn the fan on. Start the engine and starting bleeding. You'll see lots of lots of bubbles, like this.
16.) Continue running the engine--you need to get the thermostat to open, so you'll need to reach operating temp. You can hold the rpms up in the 2000-2500 rpm range. Check the funnel periodically to see that there's still coolant in it--make certain there's coolant in it while the engine is running. It took me about 20 minutes to bleed the system in cold wintertime outside air; once you have the radiator fans kicking on and off for a few cycles, you'll know that everything is open and coolant is running through the whole system. Protect your hand from heat and lightly squeeze the upper radiator hose to gauge the bleed (as you get closer to having it done, there will be fewer and fewer bubbles caused by squeezing that hose). You're done bleeding when the bubbles are done surfacing. Turn off the car. You'll notice that you'll still have coolant in the funnel, but that's fine--just cover the funnel. When I was done bleeding it, before it cooled all the way, it looked like this:
As the engine cools, it will draw that coolant back in. After about 1 hour, you'll see this:
That's the coolant all back in, where it belongs. The coolant level should be up to the "throat" of the radiator filling "neck", so that when you open the cap, you can just see it.
And you're done! Replace the radiator cap and check your reservoir level. Clear the engine of tools and Mountain Dew cans, and enjoy the fact that you know have HEAT the next time it snows!!
[Final Notes: You can use this opportunity to do an oil change and coolant change while you're at it, but this DIY just shows the steps for drain-and-refill.
For my sister's '99, the coolant was horrible and hadn't been changed since who-knows-when, so I did a full coolant change on that one. For my '00, I'd just changed the coolant a few months ago, so the coolant was fine, therefore I just drained it and refilled with the same coolant. Again if you do this, be sure your system is fully bled and full before you start, and then you'll know to just put back in what you took out. Also, since you're going to remove the oil filter, you might want to just change that and the oil if you feel like it. If you want to do that, then add a 9/16th wrench to the list and a drain plug gasket (I think its M12?), and drain the oil pan first, then close it & refill the engine with oil--you don't want to forget that part later and start the engine with no oil! If you don't want to do an oil change, just do this after the car has sit a while/overnight, and you won't lose any oil when you remove the filter.]