My other thought is that some medications have short term memory problems as a side effect. Is your brother on any medications ? If her is, he could go to www.drugs.com , type in the name of the drug and see if memory issues are a side effect. Finally, is your brother having sleeping problems ?
For some vehicles, you're advised to change the coolant every 30,000 miles. For others, changing the coolant isn't even on the maintenance schedule. For example, Hyundai says the coolant (what many refer to as antifreeze) in most of its models should be replaced after the first 60,000 miles, then every 30,000 miles after that. The interval is every 30,000 miles on some Mercedes-Benz models, but on others it's 120,000 miles or 12 years.
Antifreeze is a liquid used to cool engines. It is also called engine coolant. This article discusses poisoning caused by swallowing antifreeze. This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should call your local emergency number (such as 911) or the National Poison Control Center at 1-800-222-1222. See also: Ethylene glycol poisoning.