Merging onto the highway this past January (Jan 2016), my vents started blowing a heavy mist of coolant. Obviously, my heater core had ruptured.

The dealer was able to replace it and it worked great till about June. Once again, I was merging on the highway, and the vents blew out a huge mist of coolant. I was frustrated, but the dealer replaced it again (this time under warranty of previous work). They flushed the block with vinegar 10-12 times. Said they kept getting rust out. Everything was fine after that.

...Till last week. I passed someone on a two lane road (similar throttle to merging on the highway). Once again, the vents blew a very large mist of coolant.

What could be causing this?

The dealer things the block is acidic. Is this even possible? I know the coolant can become acidic, and I know the block can have a charge due to an electrical problem. But I don't see how a properly grounded iron block can be "acidic"?

Am I missing something, or is the dealer scraping for something to tell me?

Third time in 8 months. I don't think the dealer is fixing the core issue (no pun intended).

Truck is a 2010 year model.

 

Vinegar is an acid, ascetic acid. Vinegar will also dissolve calcium depostis if tap water has been used in the system. I only use distilled water in my cooling system. If it isn't flushed out really well, the vinegar could be causing the problem possibly?

 

In 1997 there was a TSB to add a restriction in the inlet of the HC. Basically coolant was flowing too strong to make the 90* end down into the HC. And the coolant would actually blow out the neck of the HC

This truck is several generations later, but still the same basic modular 4.6/5.4 architecture