Radiator water relation with exhaust

[Rubba]

The car is running very well and radiator coolant was decreasing to the half every 60km. nothing is coming out from the exhaust and i have checked the radiator system , nothing came up. I suspected it was the radiator it self, so i moved on.
Last week i was driving at night i ran over a hole in the road i didn't see it, the car was running loud and it was running like a ricer car lol, i immediately said it is the exhaust manifold because the sound was coming from the front. That night almost 4 riced cars was revving at me and tailgating xD
Next day after i was home i have changed the manifold since it was cracked and also the catalytic converter because it was clogged.
After running the car for a while the water didn't decrease anymore ._. So i'm really confused :/

Also when i was running 140+ kmh i feel a heat from inside the car, but now it's gone.

[eljay]

Could you be more specific about "coolant decreasing to the half"? Does this mean that you had to add half the capacity of the coolant (~1.5 gallons) or is it only half of the coolant expansion tank/reservoir? Did you actually add any coolant every 60km? If yes, how much and how many times?
If it was only decreasing to half the expansion tank and now you've noticed no heat, you may just have a bubble in the system and should bleed it properly.

[Rubba]

Yes i had to refill it over and over, if i don't add any coolant the reservoir will be empty.
After 60 km it will decrease to half (maybe lower or higher) depending on distance and way of driving.
But now it's fine again with no obvious reason.

[coffeysm]

Could be a hose, leaking radiator, and/or something that only expands when it gets hot under pressure. Try renting a pressure tester from an auto place and see if it can hold and look for leaks.

I know on my 3.0 I think I'm losing coolant from that front pipe with the bleeder screw. It's all white and flaky looking, I have a new pipe and bleeder screw that will be going in when I do the timing belt soon.

[blitz2190]

there is also a chance its the cap to the reservoir, they sometimes fail at higher pressure and leak. I had to chase that one for a bit on my friends car when we did a pressure test and nothing leaked because the tool required us to remove the cap and it tooks its place.