Campro Check Engine light on

Hi all. My brother's car (Gen-2 1.6 MT year 2004) got overheated because of thermostat failure. After he changed the thermostat(original proton) the engine goes well for about 2 months then it got overheated again also because of thermostat failure. He changed the thermostat(ori proton) and do the top overhaul but the engine got overheated during the test by the mechanic. The mechanic expected the engine head got warped. He said usually Campro head cannot be skimmed but he knows a machine shop who can skim the Campro head perfectly and he claimed he has done 3 similar cases before without any further issues. After the engine got skimmed, the mechanic also cleans the radiator and change the water pump. After the engine head been reinstalled the mechanic found out the RPM got crazy(went up and down crazily). He went for compression ratio check and did the retuning but still got the RPM problem. Later he took out the thermostat and the RPM problem settled. Later got new problem, the Check Engine light will start to turn on once the the engine reaching 3500rpm. My brother went back to the mechanic for few times but still no change. He also tried to bring his car to other mechanics but still got the problem. The temperature is fine, never exceeding 90 degree celsius, but during driving it went lower than usual. But my brother cannot drive his car calmly as the Check Engine light still turned on once the RPM went 3500. Any opinion sifus?

xtremeleo said:

in dis case, i think its wise and may be ur best bet if u can get to any proton sc and ask them to do diagnostic check via a computer. dis check will pinpoint directly u to what is causing the engine check light to emit

Click to expand...

The diagnostic(as well as the tuning) has being done at proton SC after the first time Check Engine light turned on(the mechanic brought it there since he didn't have the diagnostic tool) and it detected the sensor failure(or something like that, I can't recall) but when the sensor being replaced, nothing changed so the car went back to the Proton SC for diagnostic and again it detected sensor error. This happened few times(and back to Proton SC for diagnostic). Finally we changed all the suspected sensor but still the Check Engine light turned on. My brother try to ask an opinion from another mechanic(other workshop) and the mechanic said as for the sensor it might be the Knock Sensor failure since he said from his experience, sometimes after the top overhaul(during dismantle and reassemble) the sensor might being damaged.
I've done my own research on the internet(2carpros.com) and I found out that they claimed "When a thermostat malfunctions it can stick in the closed position not allowing the coolant to circulate, causing the engine to overheat. This will cause the vehicle to overheat in a very short amount of time (about 5 minutes). Or the thermostat could stick open causing the engine to run too cold. In this case the service or check engine soon light could illuminate, followed by a trouble code."
Also in the internet, another mechanic also stated the same but he said it not happens in all cases and that's why I think they(both mechanics) stated could/might be illuminate instead of will illuminate. I think the situation where the thermostat stick open is same with the situation where my brother is not using the thermostat now isn't it? I've ask the Proton SC technician(during the diagnostic) either by not using the thermostat could causing the Trouble Code or not, but he wasn't sure. This morning my brother came to my house and he found out little oil(seems like the hot oil vaporized from the head gasket) came out from the head gasket. Is this leak can cause to Check Engine light turn on?
Please all sifus help my brother.

Thanks xtremeleo, pm sent.

amTonjet, yea a real headache. I'll post the cause once the problem being settled.

edi78: Yea might be your car got hantu haha

Anybody experienced this similar problem before? Any solution? Mind to share?