How many watts of your solenoid?
if it requires 4 watts for continuously holding, it works ok and only warm/hot, But if it is a 6 watts or more solenoid, it will burn, and will give potential problems.
High wattage solenoids are not bad, but for our application, are bad. We only have really low flow rate of co2 gas in our aquarium co2 system, but high wattage solenoids are designed for much larger flow rate(and high pressure holding capacity), the fast flow media/fluid can carry away the heat in these high flow solenoids. In our co2 systems, co2 gas never flow fast enough to carry away the heat-the high wattage solenoids will burn and fry.
Solenoids about 100psi rating, 3 watts and below power consumption are perfect for our co2 systems, some are even better such as clippard mouse solenoids and numatics solenoids, they are below 1 watt. There are even rare and expensive 0.5 watt solenoids, Parker(900) or Burkerts(2822). These solenoids are expensive and not readily available in commercially available co2 system.