The following is a guide, I have no idea of your mechanical skills, tools available, etc. I take no responsibility if something goes awry.
On the sticking throttle body, check that the throttle cable is installed properly and lube the cable. You can disconnect the throttle cable and see if the throttle body still sticks, if does, spray some Seafoam in there to try to clean it up.
Radiator Flush:
WARNINGS:
Radiator coolant is very toxic and animals love it so catch and dispose of it properly.
The coolant system when hot is under a lot of pressure, if you open the cap you are likely to get badly burned so just don't do it.
CAUTIONS
Using a power washer to pressurize the system may cause damage, you were warned
Doing all of this and reusing hoses that over three years old is a waste
When there is only water in the system if temps drop below freezing you are likely to damage your engine and coolant system
Things you need
- Anti freeze, 2 gallons - I use Prestone Concentrate and not the 5 year stuff - antifreeze becomes acidic after three years and should be replaced regardless of what that 5 year stuff says
- Radiator flush and cleaner - I usually use Prestone
- Distilled water about 6 gallons
- Now would be a good time to replace your radiator and heater hoses if they are over 3 years old or you have no idea how old they are
- Replace thermostat, I use only genuine Toyota here because I haven't found an aftermarket thermostat that works properly. The Toyota thermostat has a larger valve to let more coolant through and it has a weep hole that must be positioned so it is up when installing.
- Replace the coolant reservoir to radiator hose, I believe it is 6mm
- New radiator cap
As for flushing that pesky clogged heater core, is the heater on in the car when you flush it, if not you aren't flushing the heater core on most cars.
1) Make sure your climate controls are in the heat position
2) Drain the coolant into a basin don't forget to drain the coolant reservoir
3) Disconnect the heater hoses
4) Stick a water hose into or at least up against one side of one of the hoses until the water comes out clean, if it won't flush, pour as much vinegar or you can use some radiator flush into the core as you can get to go in and let it sit about 20 minutes or so, retry the flush procedure from both hoses. If it won't budge you can try a power washer without a nozzle on it. The worst you can do at this point is make it leak, if it is so clogged it won't open without the pressure washer, you have nothing to lose because your alternative is a new heater core anyway.
5) Repeat from the opposite direction to ensure the core is back flushed, the water must come out clean
6) Put your hoses back on, or better yet install new hoses, heater core flush is complete
Now back to the rest of the coolant system
1) Refill coolant system with only fresh water
2) Add a bottle of a quality radiator flush, I prefer Preston but it's up to you.
3) Take a nice long drive at least 30 minutes to an hour with the heater on.
4) Let it cool down, remember you no longer have any anti-freeze in there so if you are in a cold climate don't let it freeze
5) Drain again
6) Refill with clean water
7) Now let's go on another 30 minute or so drive with the heater on
8) Let it cool again
9) Drain again, if the water isn't clear, repeat the engine flush.
Now to flush the engine
1) Make sure that heater is still on
2) Remove the thermostat, on the RAV4 you will have to remove the oil filter to get to one of the bolts
3) Put the thermostat housing back on without a thermostat, it may leak a little but that's okay
4) Replace the oil filter
5) Remove the lower radiator hose at the radiator
6) Remove the upper hose at the radiator
7) Using your water hose with a rag wrapped around the end to act as a makeshift seal, insert into the upper hose
8) Run the water until it comes out clean
9) Repeat steps 22 and 23 using the lower hose
10) Reconnect the upper and lower radiator hose to the radiator
Now it's the radiators turn
1) Disconnect both hoses from the engine
2) Flush the radiator following the steps 22 through 24
3) Install the new thermostat, remember you will have to remove the oil filter, so now wouldn't be a bad time to do an oil change if it's due
4) Reinstall your radiator hoses or better yet your new hoses
And last but not least the coolant reservoir flush
1) Disconnect the hose to the radiator and drain
2) Fill with hot water and using a long handled brush stick it in there and scrub her clean. You can use some vinegar if needed. A power washer can help as well, put on a wide spray.
3) Replace the old deteriorated reservoir hose
Now to flush the city water with all it's minerals out of the system
1) Fill the system with only distilled water (capacity is 8.5 quarts)
2) Take on a short drive or let it idle with the heat on for at least 20 minutes
3) Let cool and drain.
Now to refill. As you are refilling you can burp the radiator hoses by squeezing them. Remember the capacity is 8.5 qts but you won't get that much in there because the heater core and parts of the engine will retain some of the distilled water
1) Put in 4.5 quarts of antifreeze
2) Fill with distilled water until very nearly full, this is because when you run the engine it will burp the system and the air bubbles will waste your new antifreeze.
3) Put a 50/50 mix into the coolant reservoir until it reaches just above the cold line.
4) Run the engine, heater on, and with the radiator cap off to allow it to warm up and burp itself, keep topping it off until you can see the water circulating in the radiator
5) Put the cap back on and take it for a test run, keep an eye on the temperature gauge. After the drive check the coolant level in the reservoir it may have gone down as the engine finished burping and pulled more coolant in. Recheck after driving for a few days.
Wow, I know that is long, detailed, and a lot of steps but, depending on how bad your cooling system is it may very well need it. And I know a lot of people will shake their heads and say all of this isn't necessary, and on a system that is properly maintained and not clogged anywhere I would say yes but on a poorly maintained system with clogs this will usually fix them unless the only way is new parts.
Another point, on my car the temperature gauge had slowly moved upward towards the big H and so I replaced my radiator and upgraded the cooling fans and now her temps are better than when I bought her.
One last word of wisdom, Mobile One is your friend, the engine lubrication system also goes a long way towards cooling the engine, not going into all the details here but synthetics are let's just say slippier that conventional oils, don't break down under heat, won't foam, and stays on the parts when the engine is left sitting for a while. In extreme cold climates it is the only way to go as oil gets too thick to properly lubricate the engine. Okay, I know I didn't use a lot of scientific terms here but I just wanted to state my case.
Let me know if this helps at all.
