Bubbles Everywhere: Cavitation and the Cooling System [E220]
Thanks to our Partner, Pico Technology
Matt goes down a rabbit hole on the science of bubbles and comes back with something surprisingly practical: cavitation is a major source of cooling-system component damage, especially in and around water pumps. The “bad guy” isn’t the bubble forming—it’s the bubble collapsing, releasing intense localized energy, micro-jetting, and shock waves that pit and erode metal surfaces over time. The takeaway: approach cooling-system maintenance as anti-cavitation prevention, not just “keep it from overheating.”
Key topics covered
Why cavitation damage is often misattributed to electrolysis (and what’s actually happening)
The real destruction mechanism:
- Bubble collapse → extreme localized heat (doesn’t “cook” the system, but signals energy density)
- Micro-jet stream through the collapsing bubble “donut” → pitting/erosion
- Shock wave effects (ties into why ultrasonic cleaning works)
How bubbles form even in a pressurized cooling system
- Localized low-pressure zones behind an impeller blade
- Pressure drops along surfaces and restrictions (design or contamination-caused)
Why “radiator cap” is a misleading name
- Better term: degassing cap
- It maintains system pressure (key to preventing local boiling) and “burps” gas/vapor out
Coolant chemistry isn’t just freeze/boil protection
- The inhibitor package forms a protective barrier on internal surfaces that absorbs cavitation attack
- Over time that protection depletes → cavitation damage shows up
Water quality matters more than most people think
- Minerals/impurities can create deposits → restrictions → pressure drop zones → bubbles
- Contamination can also become nucleation points for bubble formation
- Distilled/RO water or properly formulated premix is the safer play
“Universal coolant” skepticism
- Use proper coolant type for the application—chemistry and inhibitor packages matter
Practical takeaways for shops
Start treating cooling-system service as evidence-based prevention
Testing and inspection that should be part of regular maintenance:
- Degassing cap pressure test (rated pressure matters)
- Coolant concentration (ideally with a refractometer/hydro refractometer)
- pH testing (imperfect, but can hint at inhibitor depletion)
- Voltage potential test with a DMM (if present, verify grounds and consider additive depletion as a possible indicator)
Recommend coolant replacement based on:
- Test results you can measure + time/mileage intervals (what you can justify)
Customer communication angle (the “why they should care”)
A simple way to explain it without going full science-documentary:
- “Coolant doesn’t just prevent freezing and overheating—it protects the inside of the cooling system.”
- “Over time the protective chemistry wears out, and tiny vapor bubbles can collapse and pit metal surfaces.”
- “We’re restoring protection, verifying pressure control, and preventing long-term erosion.”
Memorable moments / quotables
- “It’s not the bubble forming—it’s the collapse.”
- “We don’t think about cooling-system maintenance from an anti-cavitation point of view.”
- “We should stop calling it a radiator cap… it’s a degassing cap.”
Thanks to our Partner, Pico Technology
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Contact Information
- Email Matt: mattfanslowpodcast@gmail.com
- Diagnosing the Aftermarket A - Z YouTube Channel
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