Overheating problem on lexus es 300

Hi everyone, i own a lexus es 300, 2003 model and just recently the temperature guage started to exceed half mark. I use toyota recommended coolant and i have no idea what the problem is. I live in nigeria where the practice concerning car cooling systems that seems normal to everyone is once a car comes into the country the thermostat is removed and the fans are connected to ignition with a relay so it runs continuously so long as ignition is on and the coolant runs into the engine irrespective of the engine temperature. The mechanics here believes the temperature at the tropics is not suitable for the operations of a thermostat and hence would result to the car running hot.

One day i drove a short distance in a hot afternoon, i opened the hood and saw my upper radiator hose is swollen but the temperature is at the half mark. Next day driving, it was going up towards the red danger zone and i had to off the engine. I opened the hood and the coplant reservoir is boiling like a pot of water and overflowing, spilling on the ground till the radiator is empty
I got another coolant in there and drove again same thing happened. I called a mechanic and he said i have to take out the thermostat and run the fan straight to ignition with a relay. I figured that might be the only option so the car can move without damaging the engine. I got them to do it for a little token, the fans will come on once the ignition is on until the ignition is off and the temperature guage is running super cool, hardly up to the half mark and car is no longer overheating after the thermostat is removed.

I got home with the thermostate, put it in a pot with water and started heating it. The thermostat opened as the temperature got to boilimg point and closed as i took it out.

I am plannimg to return my car cooling system to default settings with a new thermostat in place but i am not sure what the problem is. My closest guess is that maybe the thermostat is opening at a higher temperature other than 82 degrees celcius for which it is rated and is causing the engine to run hot. So are there thermostats with lower temperature rating, say 60 or 70 which i can use? I am aware of the diadvantages of this setup on the engine efficiency and i want to revert to factory settings.

If removing the thermostat and wiring the radiator fans(s) so they run all the time doesn’t prevent the engine from overheating, means there’s something else causing the engine to overheat.

A leaking head gasket is one possibility.

Or a transmission that’s overheating.

But it sounds like you’re putting a band-aid on something that needs stitches.


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What i am saying is they prevebted the engine from overheating. The engine does not run hot anymore and the temperature guage is hardly ever upto the half mark only after just the thermostat was removed.

You shouldn’t have to remove a thermostat to prevent an engine from overheating.

Something else is wrong.



Yes i agree. I am suspecting the thermostat is opening at a higher temperature. So i want to get a new thermostat then flush the cooling system and hope for the best.

It could be the radiator is partially plugged up.

We have lots of very hot areas, like Arizona, and folks don’t have to remove thermostats.

I had to replace my ES300 radiator when it developed a crack next to the upper radiator hose connection, because of bad motor mounts allowing the engine to rock back and forth.


Yes, i know that too. The mechs are prettymuch ill-informed. I will get a new catalysts, and flush the cooling system.

This sounds exactly like what someone would need to do if they plan to use straight water as coolant instead of using antifreeze which has a higher boiling point. Do they generally use straight water in all their vehicles?

I think proper vehicle maintenace is kind of a disaster in Africa.

Inspect the radiator cap, factory caps break after about ten years. A cooling system that is not under pressure will boil at 105 C.

The cap on the left is broken;


Straight water boils at 260 F under 16 psi. Toyota long life coolant boils at 268 F with a 16 pound cap.

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@texases said the radiator could be partially plugged up

I like that idea

And I’ll add something . . . if it is plugged, is it because of a bad head gasket, or plugged up with minerals?

If it’s plugged up with minerals, then you replace the radiator and most of the problems will be fixed

If it’s plugged up because of a bad head gasket, replacing the radiator is only treating the symptom, not the root cause

I think the proper 1st step is to check for hydrocarbons in the combustion chamber, using something like this


Do the mechanics in your area have access to these kinds of tools?

I don’t mean this to sound insulting, but the fact that “standard procedure” seems to be removing the thermostat makes me wonder just what’s available . . . and I’m talking tools AND skills

Just how long are you hoping to drive this car?

if it’s just a year, a bandaid fix may be appropriate

If it’s 5 years, a proper repair is a better bet

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Replace both thermostat & radiator cap, replace coolant if hasn’t been done in past two years, bleed air from cooling system, make sure cooling system is proper level. Next, make sure engine compartment fans are working properly. Should come on if coolant is overheated (for example long idles, stop and go driving etc) , and when A/C is first turned on. Some engine fans have two speeds. If so on your car, make sure all fans are working at correct speed. Test new thermostat in pot of hot water on stove w/thermometer to make sure it opens at correct temperature, and correct opening dimension.

If after all that the car still overheats, report back for more ideas. Removing thermostat not good idea to solve overheating problem b/c thermostat regulates which % of coolant goes to engine vs radiator. With no thermostat too much could be going to radiator and not enough to engine.

Note: When engine overheats turn on heater to max. That will provide some temporary engine cooling. Likewise turn on AC, as that should turn on engine compartment fans.

Don’t want the expense or hassle to replace radiator cap? Look at the photo’s above in Nevada’s post. See the round gasket? That gasket could be cracked, but crack very difficult to see, which allows the coolant lose pressure & boil at too low of temperature. Had that occur on my truck, new cap solved problem immediately.

One way to assess if radiator is clogged, fill it w/water, then open drain. There should be a pretty good stream of water coming out at a quick rate. I’d guess around two gallons per minute. If it just sorts of dribbles out, radiator may be clogged. Dribble could be caused by clogged radiator drain valve too though.

Some years of the ES would build up road dirt between the air conditioner condenser and the radiator, which would basically block a big chunk of the radiator from getting airflow for cooling. Especially if you run the AC, you can get an overheat.

The solve is simply to clean that gunk out (which is easier said than done sometimes, since it’s hard to get at).

One guy from west Africa sucks gasoline in his mouth with a tube and then blows it back out in to the carburetor as a daily procedure to get the car started it seems! The video is in French. https://www.youtube.com/watch?v=rR-5yD3cTKo The starting procedure is at 3:25.

Then maybe it’s expected that the cooling system isn’t going to be pressurized over there. There was a diesel truck that was over heating in Africa. The kept having to stop to add more water. The problem, according to them, was that one of the brakes was sticking, which caused the engine to over heat due to excessive load.

I understood yoir point. These kind of tools are sadly unavailable here. I will start by taking my radiator to car wash for them to clean it up, then see if it helps. I will get a new thermostat too. I can’t afford another car so i will keep this one in good shape but mechanics here do not help.

Radiators contain a bevy of delicate, easily bent fins. Those fins must remain straight & parallel to each other so the air can move though them. Suggest to use caution at the car wash. You don’t want the fins to get bent over by a high pressure wash, and block the airflow through the radiator. BTW generally the problem with a “dirty” radiator is on the inside, not the outside. Often you can clean them up w/a reverse flushing process; i.e. remove radiator, pour water inside, then turn upside down and pour the water and the debris it contains out.

There are many ways to test for head gasket leaks. They often (but not always) involve a breech into the cooling system, so a very common way is to slightly pressurize the cooling system, then a head gasket coolant system leak would allow the pressure to bleed down. You’d have to rig up a way to pressurize the cooling system, say a bicycle pump w/pressure gauge and a home-brew radiator cap with a bicycle tube valve stem. There are probably diy’er methods to test for hydrocarbons in the coolant as well , google “diy test for hydrocarbons in solution”. I noticed one there which made use of a laser from a discarded DVD player. Seems overly complicated, but if you made one you could set up your own testing business for profit. I think the chemical methods use a bromide chemical of some sort.

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