I'm getting antifreeze blowing out of the coolant bottle while towing my 5th wheel. It leaves a white dried up mess on the area around the coolant bottle and brake master cylinder. There is no water in the oil and it doesn't show any loss of coolant level.

This link may help:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-10.html#post1923468

The white dried up mess is likely from the minerals in the water. Only use a 50/50 mixture of the recommended coolant and distilled water + SCA. I would flush the whole system, including removing both engine drain plugs, and start from scratch.

Also, only use full synthetic HDDO in the engine and full synthetic ATF in the transmission. This will help the engine and transmission to run much cooler:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-8.html#post1415281