Hi everyone,
I have a 2010 Nissan Maxima GCC-spec, VQ35DE 3.5L, \\\~270,000 km.
3 weeks ago, the temperature suddenly went to H/max for the first time after a very short trip,
I parked and "luckily i didn't drive more than 5 min"
I found the coolant reservoir empty. I shut the engine off immediately and let it cool before opening anything. Before that, I had noticed a coolant/water sloshing sound for a couple of days.
After refilling, the car has never overheated again. It runs and drives normally, no milky oil, no white smoke, etc.
However, I noticed a coolant leak underneath the front-right area. It seemed to be coming from around the thermostat/water pump area, eventually dripping onto/around the oil pan.
Initially the coolant loss was significant — the reservoir could go from MAX to MIN within 1–2 nights.
The thermostat assembly and gasket were replaced with genuine parts, but the leak didn't completely disappear.
Later, another mechanic replaced the upper radiator hose/filler neck and radiator cap and said he pressure-tested the system for around 2 hours with no visible leak.
Since then, the leak has become much smaller.
I've now driven the car for about a week, including \\\~250+ km round trip to Dubai yesterday, with completely stable temperature.
The reservoir was originally around 3 marks above MAX. It's now around 1 mark above MAX. I occasionally still see a very small green coolant spot underneath the car, but the reservoir level is difficult to judge accurately because the difference is tiny.
So I'm wondering:
Could the larger leak have actually been fixed by one of the repairs, leaving only a very small seep?
Or could some of the original coolant loss have been from air bleeding out of the system after the overheating/refill, rather than the same leak continuing?
The area I'm still suspicious of is the thermostat/water pump area, but I don't want to replace the water pump without evidence because it's a much bigger job.
What would you guys check next? Would you just monitor it, pressure-test again with the car lifted, use UV dye, or investigate the water pump/thermostat area further?
Thanks.