A few weeks ago, I was driving the Prado with the 2LT-E around, and had to keep idling while waiting for the line in the bank, plus Jollibee and stuff, when I noticed the needle on the Temp gauge move to ¾’s. The Prado’s computer then gave me a beeping sound, which was so irritating. I stopped by a cousin’s restaurant and proceeded to add water, got the temperature down and headed home.

The trip home was a short 5 kilometers, and once again the needle bounced back up to the ¾’s mark.

Once at home, I ran to grab my Temperature gun and pointed it at the top of the radiator, near where the hose was connected. I got a reading of 99.7 Celsius, or roughly 211.4 F.

Normal operating temp should not exceed 180 F. So what was going on? I checked the cooling system and everything was okay.

Once everything was cool, I opened the cap slowly with a rag. Let the pressure out a bit before fully opening and this is what I saw.

What caused all the rust and grime? I checked and we have been putting in normal tap water into the Prado for almost a year now.

Time for a quick experiment. I placed a can of tap water and heated it with an acetylene torch. At 84 Celsius, the water boiled. This was well below the 100 C boiling point. I tried drinking water from the local water refilling station, and it got to 99 Celsius and started to boil. So the cleaner the water, the later it boiled. My conclusion was that my dirty cooling water caused my radiator to boil over, loosing a lot of water as the coolant reserve bottle overflowed, and the water loss led it to almost overheating.

The Procedure

1. I then flushed my cooling system with clean tap water, and decided to use radiator flush. Any brand will do, but follow the instructions carefully.

Drain a bit of water first, and pour in the radiator flush, close your radiator cap.

2. Start your engine, and get it up to operating temperature, usually around 80+ Celsius or a little over 1/3 on the temp gauge. Keep it running for another 10 minutes.

I used a block of wood to keep rpm at around 1,200. If your vehicle has a cabin heater, you should put it in High, so that it will get flushed and cleaned too.

After 10 minutes, I drained the radiator tank. The pictures I used of the draining were from the Hilux (which I also flushed at the same time), as the Prado’s radiator drain was hard to contain in a bucket.
Just imagine all the rust and dirt that came out.

3. Continue flushing the cooling system for about three to four times with tap water. Going back to step 2 every time you flush. Then flush it twice using drinking water from a refilling station or distilled water, whatever is more convenient for you.

4. Now let’s get our Coolant and water ready and follow the coolant makers mix instruction. It’s usually 50% water and 50% coolant. On this particular brand it was two parts water to one part coolant. I noticed Pre****e sells pre-mixed coolant, which is a wise choice too. We need coolant to increase the boil-over temperature of the water. Also, coolant lubricates our water pump seals, and protects our engine from rust.

5. Make sure you fill the coolant reserve bottle as well. Fill it up to max level, and start the engine. I usually keep the radiator cap open, and keep adding a bit of coolant mix as the level lowers. This flushes any air in the cooling system out. Run the engine for about 15 minutes to make sure you don’t have air bubbles in the system.

6. Inspect your radiator cap. Most rubber gaskets on the cap tend to expand when old, extending past the metal part of the cap. The expanded rubber causes the cap valve to get stuck and not release pressure at its rating, sometimes causing unwanted leaks.

What I usually do in this case is look at the rubber gasket closely. If it doesn’t have cracks and it isn’t soft yet, I just cut off the excess rubber and re-use the cap.

I have this belief that the original caps are always better.

If you decide to replace the cap, find a really good brand. I recommend Gates Safti-Vent caps, US made, very nice, but hard to find. OEM caps are great too. Just make sure you get one with the same pressure rating.

If your radiator is a bit old and might not hold high pressure, get one with a lower rating. On my old Patrol I used a Gates Safti-vent with 6psi rating.

Now we are done. I did a test run on the Prado, and after a lot of idling around with the A/C on and full power runs I got the normal temperature, and using the temperature gun, I got a reading of 78 C or 172.4 F. A big drop from the day before.

A bit of advice, don’t overfill your coolant reserve as the level rises when the engine heats up, so you run the risk of overflowing the reserve bottle. Just keep it on Max when the engine is cold.

Also make sure to recheck you coolant level the next day before you start your vehicle as it tends to lower a bit as more air is flushed out of the system.

Well, this simple radiator flush and coolant change will last you another year, as it is best to re-flush and replace your coolant on a yearly basis in Manila, as the stop and go traffic is heavy on the cooling system.