I got a call from a customer who felt his motor was running a little hot in the fall and thought he should address it during the off season. We decided to pop the caps off the heat exchanger, check it out, and take it from there.
I popped off the heat exchanger caps on a warm Maine early spring day.
Noticing the very diluted color, of the propylene glycol, I took a cup of it home and tested it with my sight refractometer. The freeze point was around 25F on a test strip but the refractometer reading was actually worse than the test strips and is far more accurate.
I called the customer to inquire about the "winterizing" process. The owner had decided to undertake the winterizing himself in the fall, and claimed to have sucked 2 gallons of -50 RV antifreeze through the system.
I now needed to pressure test this HX. After removal and pressure testing it was discovered the heat exchanger had frozen and split in the tube pack. The low temp that winter had been about -14F.. A repair like this costs a fair amount of money, and certainly far more than sucking in an extra gallon or two of antifreeze. Think about this the next time you decide to suck in "untill you see pink".... Westerbeke, the maker of this engine, suggests an entire 5 gallon bucket!!
RV antifreeze/propylene glycol is not intended to be diluted and should be used full strength. When diluted the freeze and burst points rise rapidly, because it is already diluted from the factory..
When in doubt suck in another couple of gallons or test it!!