Foaming and Cavitation in the Cooling System

Previously A1 has provided details and interesting facts relating to cooling systems.  
We have discussed coolant and compatibility and electrolysis or stray electrical current, both of which have a major effect on cooling system performance and life span.  

Now I want to share our experience on cavitation corrosion which is also a silent killer of cooling systems.                                   

Foaming and Cavitation in the Cooling System
The little bubble that causes big trouble
1. Can foaming coolant cause overheating?   Yes
2. Does a foaming coolant cause corrosion?  Yes
3. Is foaming an indication of poor product quality?  Yes
4. Will foaming shorten the life of coolant?  Yes
5. Is there a way to tell if a coolant will foam in service?  Yes

The major concern with a cooling fluid that foams is the tremendous effect it has on the circulation of coolant throughout the whole cooling system.  When a coolant foams it interferes with the effectiveness of the water pump, the effect each and every bubble is displacing fluid and replacing it with air.  A water pump designed to pump 15 litres a minute of fluid may in fact be pumping 10 litres of fluid with the balance in the form of foam (entrapped air) so the ability of the cooling system to dissipate heat is greatly reduced and overheating is likely.

A second concern about poor quality coolants that foam in their ability to induce a severe form of corrosion called cavitation corrosion or erosion, this form of corrosion is predominant in high turbulence areas of the cooling system such as the water pump.  The rear face of the water pump can be totally washed away behind the impeller in a matter of months if the foam induced cavitation is excessive.  Also cavitation becomes more severe the faster the water pump revolves, so a slow revving V8 engine will be far less prone to cavitation than a high revving V6 or 4 cylinder.

Foaming is an indication of the suitability of a product for use in the cooling system, basically the less a product foams and the quicker the foam it generates disappears, the less chance it has of causing cavitation erosion damage to the cooling system components.

A coolant that foams will shorten the life span of the inhibitor system, as the excessive amounts of oxygen constantly in the system accelerate corrosion and the inhibitors will be consumed in a shorter period of time leaving the system vulnerable to corrosive attack.

The quickest test for a product that will foam in service is to just shake the container it comes in and observe the amount of foam produced (it should be almost nil) and the time it takes to disappear (5 seconds is considered the maximum limit).  If it takes longer that this you should be wary of this product, and check with the manufacturer as to why.

A1 use the Valvoline Zerex range of coolants and corrosion inhibitors which contain the best silicone Anti Foams available in automotive use today.  Having said that there are many good brand coolants in the market so just make sure you do the "Shake Test".

We are the specialists in Automotive Cooling Solutions!