Car is fine when driving normal, eg. 60km p/h in town on normal home to store trips. Engine is overheating, when trying to reach 100km p/h or more, the car struggles, basically it starts shaking like it is trying to push more power out of the engine, but can't. The car overheats then and the engine shuts off and then I have to wait for it to cool down to continue driving, however I can start it again, but it does not have any power to go forward and shuts off again. The temperature switch was removed and the fan connected directly by a mechanic, hence this didn't fix the problem as promised. The car also backfires / misfires when trying to reach that speed. I've checked the dipstick for the oil, doesn't seem like there is water in it. However I haven't check the oil cap. So not sure if it is a blown gasket. Vehicle has 159000kms on it, and is a 2.0 16v