It was weird, it doesn't leak while it's stationary even I rev the engine up to 4000rpm for as long as a few minutes. But just 5 minutes after I hit the road, there are water all over the bottom protection shield. And the reserved coolant bottle went down very quickly, I was filling about 1 litre water/coolant for every 20 miles I drove. (that's all before getting the radiator filled up with stop leak.)
Then a few days after the stop leak stuff was put into the radiator, the leak stoped. Another 2 days later, the heating stopped working.
I thought it was the water circulation, actually I cleared the radiator just now, and filled with clean coolant/water mix. It's now heating up at stationary even on idle, but as soon as I'm on road and getting some speed, the temperature gauge actually is dropping down. feel like the circulation is not working at all, but I had coolant cap off and watched it. I can see coolant flow pretty fast.
About the thermostat, I 'm pretty sure that's not the problem, as the radiator is not heating up at all, I can touch it bear hand, it's only a little hotter than warm.
Totally no idea what can be wrong now. I might just bring it back the repairer tomorrow.
Thank you guys for the help.
Regards,
DD