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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