Introduction: Toyota RAV4 2008 Coolant Change and Thermostat Swap

About: When it comes to DIY, the more the merrier!

Hello! And welcome to this tutorial on how to swap coolant and thermostat on a 2008 Toyota RAV4. My particular model is a 2.4 L 4-cylinder (2AZ−FE) engine, 4-wheel drive.

I have pictured my beloved everglade metallic RAV4 in the above image. In 2018 (she's now 10 with ~160,000 miles on her), I decided to swap out the original coolant. While I was at it, I swapped the thermostat as a precaution.

While figuring out how to swap the coolant, I did a ton of research. Then on game day, I went over to my mechanic friend's house, so he could help me throughout the process. I figured I should make my learnings public, so I made this instructable.

As with any car work, it can be stressful. To help keep you calm (if you decide to DIY this yourself), here is a good song: Nissim by The Gaslamp Killer

Step 1: Research

To start out, I went to Google for a crash course. I found some good videos on 2008 RAV4 coolant swaps:

I hit my owner's manual (Pub # OM42672U)

Great forum:

Understand how your car's cooling system works. Watch some videos also has some great schematics for finding part numbers

Aside: Pulling Vacuum During Swap

One thing I learned is that if air bubbles get into coolant system, they can become trapped, and prevent coolant flow in that area. These areas become hot spots and can result in damage to the engine.

The way professional mechanics avoid these problems is by pulling vacuum in the coolant system, and then refilling the system with a 3-way valve. Here is a video talking more about this.

I decided to buy a vacuum kit to help purge out my coolant system. The kit cost me ~$46.

Note: I found it's vacuum gauge was not zero'd properly. I had to disassemble and "calibrate" the Bourdon tube inside by squeezing a pinch point. See the attached images for how this was done.

Step 2: Select Coolant

Reading in the owner's manual, I found:

  • Coolant capacity: 6.8 L = 1.8 gallons
  • USA (aka warm weather) requirements: premix
    • 50% "Toyota Super Long Life Coolant"
    • 50% deionized water

The owner's manual also states that if you use another brand of coolant, make sure it's "high quality ethylene glycol based non−silicate, non−amine, non−nitrite, and non−borate coolant with long−life"

As I was a good boy, I bought 1-gal Toyota full strength (aka not pre-mix) coolant from a local dealer for $39. I also bought DI water, and did the mixing myself.

Here are some non-Toyota options I found:

It seems they are all within $10 after you account for mixing. If you factor in time, then just buy premix online.

Aside: Why Premix

Some people will say:

  • Use only coolant
    • Water is actually a more effective coolant
      • It has a higher specific heat capacity than ethylene glycol
      • It's less viscous, so it's more efficient to pump around your system
  • So then use only water
    • It's cheaper and easier! With a catch...
    • Coolant only works in your system if it's liquid
      • If you live somewhere where temperatures go below freezing point, this is a bad idea since it water expands when it freezes, and can damage things.
      • Similarly, if the water boils, it increases pressure in the system, which pops your radiator cap, which means you lose coolant, and then with no coolant your engine overheats
  • Correct answer: use premix
    • Decreased freezing point, increased boiling point... larger temperature range when liquid

Step 3: Select Parts

Since I was also swapping my thermostat, I had to pick these out as well. I referred to a diagram to get the OEM part numbers. I was too chicken to get an after market thermostat.

Here are the part numbers I purchased:


  • OEM PN: 90916-03136
  • Where I bought: Amazon, $16

Thermostat Gasket

  • OEM PN: 16325-0T030
  • Where I bought: ebay, $9

One thing I will not detail in this tutorial is tools. All I will say is having the right tools makes this job infinitely easier.

Step 4: Prepare Your Car

There is a saying that painting is 80% preparation and 20% painting. Luckily with coolant swaps, this is not the case!

Initial Checklist

Here are a few things to check off:

  • Parked on a flat surface
  • Car's heater setting is on max heat
  • Car's fan setting is on max speed
  • Car is turned off and engine + radiator have cooled down since last use
    • Video talking about when it's "cool enough"

Remove Undercarriage Panel

Additionally, to access your coolant drain plugs, you will need to remove the plastic undercarriage panel beneath your vehicle.

I did not do a good job documenting this, but it's the big panel underneath your radiator and engine block. It's attached to your front bumper via some screws and to your body via some panel clips.

The reason we remove this is for ease of access, it's not necessary.

Step 5: Drain Old Coolant

The actual drain plugs take a while to find, but once you have zero'd in on them, this step is cake.

Prerequisite: a drain pan of some sort

The antifreeze in your car's coolant mix is not good for environment, humans, or animals. It tastes sweet, but causes kidney failure.

If you are curious, it's probably okay to taste a drop and then wash your mouth since it's well below a lethal dose (per this video).

I caught all my coolant using a system of buckets and closing the plugs when they filled up. I found I got probably 1 1/8 gallons of coolant out of my car.

One thing you can do to speed up draining is to remove the coolant reservoir cap.

Radiator Drain

There is a yellow knob on the back lower right (when facing towards front of car) of the radiator. Loosen the plug, and you will see coolant start to drain.

I did this one first, and would say almost a full gallon of coolant came out here.

Engine Block Drain

The drain plug is on the engine block's front-facing part. It's a different type of plug, it actually has an adapter for a hose. Loosen this one's screw, and let the coolant flow out!

Note: this one was quite rusty for me, I had to use liquid thread loosener to break it loose.

I had maybe a 1 cup of coolant come out of here.

Step 6: Optional: De-scale Coolant System

Depending on the state of your removed coolant, you may want to flush and descale your coolant system. Now is the time!

Here is a good video that kind of frames the problem. There are a lot of resources online about this, so I will not document coolant system descaling.

I found my coolant was not that dirty (in fact, I was quite disappointed... I probably didn't need to do the swap yet). Thus, I chose not to descale my coolant system.

Step 7: Remove Thermostat Goose Neck


If you look into the engine from the top, you will see your engine oil dipstick. To the left of it is your generator. In the middle and down into the engine is the "illustrious" thermostat goose neck. See the images for more clarity.

Fun fact: the neck is called "inlet, water" by Toyota. I prefer goose neck.


In other videos I have seen, people would remove their drive belt + generator to get at this. These steps are not necessary, and increase your chances of being scared away from attempting this maintenance yourself!

With a socket/ratchet extender kit + flex-head ratchet, you can complete the removal with minimal effort.

1: Hose Removal

To remove the hose attached to the goose neck. Just squeeze the tabs on the hose clamp and slowly work the hose off. There is a lip on the base of the goose neck that makes it somewhat difficult.

This is relatively easy with channel lock pliers, and is even easier with hose clamp pliers

2: Nut Removal

Next part is simple: remove fasteners. The goose neck is held on by two studs screwed into the engine block + two flange nuts. You need to remove the nuts.

On my car, the nuts were kinda stuck. It is smart to apply some thread loosener.

Another fun fact: the studs are referred to as "stud, hex lobular" by Toyota, which I thought was a funny name.

After breaking loose the nuts, I mostly took them off by hand. However, it's easy to drop these nuts, so consider using a magnetic socket.

3: Remove/Clean Goose Neck

Take a picture of this, so you remember which direction the neck bent towards. I forgot to do this...

While removing the goose neck, make sure you don't scratch the sealing surfaces (aka hose clamp part and base face).

Next, wipe the sealing surfaces clean with a wet rag, just to make sure everything seals upon reinstall.

Step 8: Replace Thermostat

Look at that beautiful thermostat sitting in there!

Thermostat Considerations

The thermostat is basically a passive poppet valve. If you are going to replace it, learn how it works:

And understand its main failure modes + consequences:

  • Stuck open: coolant always goes to radiator --> coolant too cold --> engine runs cold
    • Increased fuel consumption + higher emissions
    • Equivalent of not having a thermostat. Why this is bad.
  • Stuck closed: coolant never cooled down --> engine overheat
    • Engine overheat is very bad and can result in multi-thousand dollar repairs
      • Warping of cylinder heads/engine block
      • Head gasket leakage
      • Water pump or crank failure

In a future step, we will discuss how to test for coolant overheat.


Replacement is easy:

  1. Take picture of original thermostat, so you know which direction it was facing, and you can show your friends
  2. Break thermostat out (mine was kinda jammed in there)
    • This may require pliers
  3. Clean surface where gasket used to be on engine block
  4. Put new gasket on your new thermostat
  5. Lubricate new gasket exterior with old coolant
    • This is to prevent gasket damage upon re-installation
    • Using another lubricant introduces foreign materials into your system, so don't do this
  6. Install new thermostat, taking note of jiggle valve/air bleed clocking

Step 9: Reintegrate Goose Neck and Hose

This is a quick step.

  1. Gingerly slide goose neck back onto studs
    • Take care not to cause debris to get onto gasket or sealing surfaces, or you could get leaks
  2. Reinstall flange nuts back onto studs
    • Progressively tighten nuts so as you evenly load gasket
    • If you don't do this, you risk a leaky goose neck
  3. Reinstall hose onto goose neck
    • If you want it to look professional, place hose clamp in original indents, so you it looks untouched
    • Be ginger, if your hoses are old (mine are over a decade old), the rubber becomes vulnerable to cracking

Step 10: Add in New Coolant

Getting into the final stretch here. This is a fun step.

My Vacuum Attempts

I first tried to be a professional and pull a vacuum on my coolant system (see the Research step for why).

Besides enabling a faster coolant swap, pulling vacuum does two things:

  • Lets you check coolant system for leaks
  • Ensures you have no air bubbles in system

First, I discovered the air bleed port on the stem of the coolant reservoir's cap. I plugged that with a bit of butyl rubber. I was now able to pull about 40 cm Hg of vacuum on my system.

It was enough to flatten all of the hoses, you can see this in the attached pictures.

I was annoyed that it was not better, and I went through a process of elimination with some hose clamps. I ultimately found the coolant reservoir lid was leaking enough to defeat the vacuum. This was a bummer, as it meant I was not going to be use the vacuum for the coolant swap.

Adding in New Coolant

I was forced to go with the old-timey method of:

  1. Pour coolant mix into reservoir
  2. Wait for it to drain into system
  3. Repeat steps 1 - 2 until system was full
  4. Start engine. This causes coolant to cycle and works out air bubbles
    • I also squeezed hoses a bit to get the extra bubbles out
    • Some cars have bleed valves to make this process go faster. As far as I could tell from a bunch of research, the RAV4 has no bleed valves
  5. Top off reservoir again and again until it stops sinking while engine runs
    • You want engine to get up to temperature, ensuring the thermostat has opened
  6. Fully tighten radiator cap
  7. If you did successfully pull vacuum, remember to remove the butyl rubber plug on the coolant reservoir's air bleed port

Make sure you add back enough coolant. In my case I removed about 1 1/8 gallons of coolant. Make sure you add at least this much back into the system.

Step 11: Check for Leaks and Test Thermostat Functionality

This step can be done in tandem while topping off your coolant in the previous step.

At this point in time, you can hang out for a bit while waiting on your engine to warm up

Check for Leaks

Just monitor all leak points in your system (aka the points you just touched) while your engine warms:

  • Both drain plugs
  • Goose neck base and hose

If a leak springs up, that really sucks.

You should continue to check your coolant level in the reservoir for several weeks after this job. If you find coolant level drops a small amount once, top it off and know an air bubble probably got out. If it repeatedly drops, you probably have a leak.

Test Thermostat Functionality

I will refer you to other tutorials for this: article

What I did was just make sure my car got up to running temperature, and then stayed there while I drove it around.

You will want to constantly monitor engine temperature while driving for several weeks after this job.

Step 12: Summary

Wrapping Up Job

Once you have verified initial functionality, re-install the plastic undercarriage panel.

Congrats, you are now done! As I said in the last step, just monitor your engine temperature and coolant levels. Hopefully you will find everything is working nominally.


I would like to say thank you for reading this tutorial. Hopefully it answers some of your questions, and that you feel more comfortable/knowledgeable about coolant/thermostat swaps.

My one piece of advice is if possible, invest in getting the right tools. This job is made so much easier that way.

Since I am new to coolant swaps, I put in 10+ hours of research on everything. The actual job took me about 3 hours (I screwed around with vacuum thing for a while). When this RAV4 reaches 300,000 miles in 2030, I will reread this tutorial and perform this job in an hour. ;)


I am always looking for recommendations/improvements, please post your comments if you see any gaps in the tutorial, or have general advice. Thanks again!