I've had three Sonic and, eventually they all do this. The current offender is the 2013 LT Turbo Sedan with only 23k miles on it.
There is just enough air that has worked its way into the heater core that the pipes rattle upon acceleration when they are full of air. It is most noticeable on takeoff around 1500 engine rpm. The heat works after a few minutes (seems normal) and then the rattling stops.
No leaks anywhere and passes pressure test.
So, I've bled some air out by opening the pressure cap while still warm, and the reduces the rattle somewhat. But, you can tell there is still some air in the heater core by compressing the hose going to the top firewall connector. Its full about 3 inches below the fitting and empty above that when cold. When warm it is full.
I've also tried the funnel approach and that really does not work well, since the heater core is ABOVE the reservoir. Trust me - it is...
Since this is a recurring problem, really just an annoyance, I'm thinking outside-the-box here. It would be nice to have a bleed/fill port near that top connector. The hose is 3/4 inch, and I found the $2 connector online (link below.) Seems like it would work, but I'm not sure if I can/should run 3/4 hose directly to the aluminum tube with a clamp or retain the factory snap on fitting. Retaining the fitting may cause clearance issues and I want to lose as little coolant in the process as possible.
Let me know your thoughts.
https://shop.advanceautoparts.com/p/dorman-help-3-4-radiator-flush-tee-with-cap-47120/22140361-p
There is just enough air that has worked its way into the heater core that the pipes rattle upon acceleration when they are full of air. It is most noticeable on takeoff around 1500 engine rpm. The heat works after a few minutes (seems normal) and then the rattling stops.
No leaks anywhere and passes pressure test.
So, I've bled some air out by opening the pressure cap while still warm, and the reduces the rattle somewhat. But, you can tell there is still some air in the heater core by compressing the hose going to the top firewall connector. Its full about 3 inches below the fitting and empty above that when cold. When warm it is full.
I've also tried the funnel approach and that really does not work well, since the heater core is ABOVE the reservoir. Trust me - it is...
Since this is a recurring problem, really just an annoyance, I'm thinking outside-the-box here. It would be nice to have a bleed/fill port near that top connector. The hose is 3/4 inch, and I found the $2 connector online (link below.) Seems like it would work, but I'm not sure if I can/should run 3/4 hose directly to the aluminum tube with a clamp or retain the factory snap on fitting. Retaining the fitting may cause clearance issues and I want to lose as little coolant in the process as possible.
Let me know your thoughts.
https://shop.advanceautoparts.com/p/dorman-help-3-4-radiator-flush-tee-with-cap-47120/22140361-p
