Did coolant flush 3 weeks ago and right after till today I can hear loud sloshing noise inside the car coming from vents when car is cold (overnight). After few minutes of driving when it's close to operating temp the noise is gone.
The noise increases with engine rpm and car never behaved like that before the flush.
What I did was:
1. Flushed old fluid.
2. Poured in distilled water with radiator cleaner additive, ran the car according to cleaner instructions, flushed out dirty mix, checked out thermostat for any debris.
3. Poured in new distilled water,ran engine, flushed, repeated 5 times till coming out water got clean.
4. Poured in new 50/50 coolant mix, ran the car with radiator cap off using spill free funnel with heating on max, revved engine a bit few times, some big bubbles came out.
Then after week ago tried to burp the car again with front on the jack for higher radiator point. No changes.
Seems there is no leak in the system because coolant level in radiator and reservoir is still at same full level after 3 weeks, daily driven.
It's blowing hot air while heating on max and carpets are dry.
My last hope is to flush heater core alone back and forth with garden hose.
Car is 2006 Evo IX.