Hi, I have a 2002 Toyota Prado that has been overheating recently. we just had the radiator
and waterpump replaced as we thought that was the issue but that didn’t fix the issue. We then went on the replace the Thermostat and it is still Overheating.
So we assumed that maybe the head was cracked or maybe the gasket was bad so we took the head off had it pressure tested and skimmed and then replaced the gaskets for the head and all the manifolds. And it is still overheating.
We think the block might be cracked but it isn’t blowing smoke and the water isn’t leaking or mixing with the oil and the car runs fine other than it overheating. Turning on the heater cools the engine down for some reason. We are completely stuck and don’t know where to go from here if you have any advice that would be great. Thanks for the help 
Oh my… i hate to suggest that all that work might not have been what was needed.
You more than likely have air pockets trapped in the cooling system.
There are several ways to correct this condition. Sometimes there are bleed nipples on the rad or near the T stat housing… other times you simply need to carefully warm up and allow complete cool down of the engine to “burp” the air pockets out… this usually takes about 2-3 Hot and Cold cycles to accomplish this.
With the rad and overflow tank completely filled to the top…install the rad cap tightly and warm up the engine to normal temp… do not allow it to overheat and BEWARE… your engine temp gauge cannot be relied upon to be accurate with possible air in the system. After the engine is warmed up… you then allow it to cool down completely as in… Cold… as if u never started the vehicle. This is an essential step because as the coolant coola down, it contracts, taking up less space… with the rad cap on tight and no other leaks in the system whatsoever… this will create a vacuum and will then suck liquid coolant into the rad from the overflow or rad tank… doing this process several times will “burp” the air out of your system and make it ready to use the engine as normal. Of course pay attention to the cooling fans and be sure they function… you can engage the AC Momentarily to test one of the electric fans out… then shut the AC off again.
The engine will tend overheat with those air pockets in place… its actually very common and very important to get the air out…
I’d bet that is all you needed to do from the get go…as well as be sure your fans are functioning
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Another possibility is that the fan isn’t working. Have you checked it? As for the heater, it’s basically a second radiator. When you turn it on it helps cool the engine. I used the heater that way on a Pontiac with heating related issues.
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