Causes of Bulging Coolant Storage Tanks
A bulging coolant storage tank is often a sign of excessive internal pressure, which can stem from several issues.
Primary Causes
- Faulty Pressure Cap: The cap is designed to release pressure when it exceeds a safe threshold (typically 10–15 psi). If the cap's valve sticks or fails, pressure builds up in the cooling system, forcing the tank to expand and bulge—plastic tanks are particularly vulnerable to this distortion.
- Coolant Contamination: Mixing different coolant types (e.g., ethylene glycol and propylene glycol) or introducing oil into the system can create chemical reactions. These reactions generate gas, increasing pressure.
- Blown Head Gasket: Can leak combustion gases into the cooling system. The gases, including carbon dioxide, get trapped, causing pressure spikes that bulge the tank.
- Overheating Engines: When the engine runs too hot, coolant boils, producing steam. Steam expands rapidly, overwhelming the system's pressure-relief mechanisms.
- Physical Damage or Aging: Cracks or weak spots from impacts, corrosion, or prolonged exposure to high temperatures can compromise the tank's structural integrity.
Warning: Ignoring a bulging tank is risky—it may eventually rupture, causing coolant loss and engine overheating. Diagnosing the root cause (pressure cap, head gasket, or overheating) is critical to prevent further damage and ensure the cooling system functions safely.