We've had to clean collectors on more than one occasion, and won't mention call letters. The photos below show one instance when coolant broke down and the collector sustained damage. The damage can be degenerative. A damaged collector does not exchange heat as well as an undamaged collector. The increased heating causes additional damage to the collector. Left unchecked, the IOT will ultimately fail due to overheating.
Here are some shots of an IOT collector that sustained some damage due to coolant failure. Click on any of the shots for a larger view in a new browser window..
Here are some shots of the same collector after it was cleaned on site. Note there is some permanent damage to the collector.