2G Overheating on idle (Stops when rev)

[polverari]

(As I always do, I apologize for any translation errors)

I have a 2g GST and I am recently having overheating problems.
Basically, the car only gets hot when I'm idling. Even with the radiator fan on (starting at 195 ºF), it keeps heating up.
What I noticed is that if I keep the car stopped, however, revs to 2000 RPM, the temperature starts to fall and returns to normal (under 194º F)
Like, if I start to ride the car, the temperature will also return to normal.

1 - The car is currently without a thermostatic valve. (I removed it, to test if it could be the problem)
2 - The water pump is relatively new (Gates), it is about two years old.
3 - The car is using coolant additive (a simple one [Paraflu] but is using)
4 - The radiator is made of aluminum, I bought it on eBay and has about two years of use, as well as the water pump
5 - Many and many tests were done on the head and all the car repairs shops told me that they did not find any abnormalities. (Compression test [150-150-150-145], tightness test, a series of tests that I will unfortunately not know how to write in English. They use a screwdriver to try to found water in cylinders, they injected compressed air into the radiator cap and cylinders, etc.)

Is there a way for me to "test that the water pump is good" without having to remove it to inspect?

I have some ideas in mind, but I would like to see your opinion, maybe I can get some valuable tips before I go for more hard and expensive solutions (remove Water Pump, remove the head, etc...)

Thanks!

 

[Mello]

I've had this problem in the past & what fixed it for me was buy a new radiator cap. Car would get hot when stopped but would cool down to normal when driving or if I rev'd while stopped. I only buy Mitsubishi radiator caps now because I've experienced leak spring on the aftermarket caps.

 

[DSMPT]

Or maybe belt tension is low or slipping at low RPM for some reason, such as old, too oily etc.

 

[polverari]

I've had this problem in the past & what fixed it for me was buy a new radiator cap. Car would get hot when stopped but would cool down to normal when driving or if I rev'd while stopped. I only buy Mitsubishi radiator caps now because I've experienced leak spring on the aftermarket caps.

Thanks! I will order a OEM one right now!

There are other caps (1.4 bar, 1.5 bar)... For "performance cars"
Is it worth?

 

[polverari]

UPDATE:

I tested a new cap (0.9 bar). Still the same problem
Also i cleaned the radiator inside, it was ok.

I ran about 80 miles today.
First 40 miles = All ok, but when i WOT on 4 Gear, car heats up and dont came back to the normal temperature. I needed to stop, wait, open the radiator cap, fill with 2 liters to go back.
Last 40 miles = I drove as smoothly as possible and the car didn't heat up until I got home

Probably i will remove the head to inspect. I don't know what else I can do

 

[Mello]

So it got hot when you got home. Was it low on coolant again also? If it was low get a coolant system pressure tester & check to see if you can find a leak that only happens hot & under pressure. Easier than jumping right into pull your head.

 

[polverari]

So it got hot when you got home. Was it low on coolant again also? If it was low get a coolant system pressure tester & check to see if you can find a leak that only happens hot & under pressure. Easier than jumping right into pull your head.

In both situations, the coolant level has dropped slightly. I returned all the liquid that was in the expansion tank (I don't know the term in English, that small tank). And yet, I managed to add another liter of water.

The question is: Even with 2 liters less, the car would still have 5 liters of coolant. It wasn’t supposed to warm up walking at 60 miles an hour on an empty road ...

That is why I am seriously suspecting that the engine is being compressed into the cooling system.

However, I did this test that you just commented (coolant system pressure tester) and the car repair shop did not find any problem ... This is what intrigues me :-(

 

[Jk's97DSM]

Operating temperature should be the middle of the gauge. At that point the fans come on to regulate temperature if needed based on the temperature sensor reading. You should have pressure on both radiator hoses. They should both be within 10-20 degrees of each other. If they aren’t you have an issue with the water pump not circulating the coolant, a thermostat that doesn’t open, or the radiator restricting flow. None of this works in any sort of good way if the system itself isn’t pressurized. Buy a cooling system pressure tester. Apply 15psi to the cooling system and wait at least 30 minutes to check it. If it drops you have a leak. Get a spray bottle and soapy water and hit every hose, pipe and flange.

 

[Matt_Hester99892]

What if u have tested all of that an it still over heard on idle? Mine has same problem but with 420a

 

[polverari]

Sorry for taking too long to answer! Well.. Finally i discover: Head gasket
When gasket have been changed, the guy didnt applied the correct torque spec and the surface paint of the metal head gasket melted...
I dont know if ive explained correctly, but.. that it

Btw, now im changing the head gasket and using o'rings on block.

Pic of whats happened:

 

[Jk's97DSM]

That doesn’t tell you anything. You’ll see scorch marks on the head gasket or mating surfaces.

 

[Bo0sTeD 4G63]

This happened to me not to long ago and it was the water pump going bad. As soon as I changed it the problem went away.

 

[Murdertalon]

Should have done a leak down test. Should also have done a coolant pressure test.