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Q: Overheating issue

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All started with a burst hose. Noticed my temperature gauge was buried in the H, so I pulled over, towed home, And replaced the hose. now I have an air leak, somewhere. The car concistantly overheats a few weeks after I top up the coolant, and burp the system. I open up the rad cap to see that my coolant level is way down. I am not able to locate the leak. No puddles form under the car, I used a block tester to test for hydrocarbons, new rad cap, new thermostat, new hoses, new radiator, (from other issue) and nothing. Pressure testing resulted in a definitive air Leak. But something new happend the other day, I was overheating while idling, and i pressed on the gas. My temp gauge went down when I did so. The rad fan always comes on no problem, new fan switch, new relay. Very strange. Checked out the timing belt to see when the last time it had been done was, looked pretty new. It may be foolish to assume that because the belt is new, the water pump is too. No milky oil, and atf is fine

My car has 310000 miles.
My car has an automatic transmission.

A: Hi there. The description you have provided...

Hi there. The description you have provided for your vehicle’s overheating problem, appears you have covered all the bases. The pressure test of the cooling system, you stated, resulted in a definitive air leak. Assuming the pressure dropped, coolant should of been visible if, the cooling system was completely full. There is still a possibility you have a head gasket and/or cracked cylinder head. I would try pressure testing the cooling system, while the engine is cold, with the spark plugs removed. As the pressure drops, continue checking the coolant level, adding to the level. If, there is a head gasket and/or cylinder head problem, coolant should be present in a cylinder or show up in the oil. Before reinstalling the spark plugs, have an assistant turn the engine over while you stand off to the side, observing whether any coolant comes out of the spark plug holes. The coolant/air leak needs to be identified sooner, than later. I recommend your vehicle be inspected and diagnosed by a certified technician from YourMechanic.

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