I just replaced the water pump new and took out the thermostat because it was stuck closed and didn't have the 40 bucks for a new one yet. When I had the van engine running and normal temp between 185 and 210 I took off the radiator cap not thinking and I had a fountain of coolant coming out of the radiator. Could this be a sign of a blown head gasket? It also has the 6.0 v8

  • Welcome to Motor Vehicle Maintenance & Repair! It should be of note, removing the thermostat is NOT a good thing. Many of today's engines use the thermostat not only to control/maintain engine temperature during operation, they also control direction of coolant flow throughout the engine. By taking the thermostat out of the engine, you can cause unforeseen issues which may exhibited as other issues. Really, get a new thermostat in there as soon as possible. As an aside, I believe fred's answer/advice to be spot on. Mar 30, 2018 at 11:18
  • is this an actual radiator cap, or the cap on the overflow tank?
    – agentp
    Mar 30, 2018 at 22:21

1 Answer 1


The coolant system of a typical internal combustion engine is designed to operate at greater than atmospheric pressure. In so doing, the temperature of the coolant can be raised above "normal" boiling point.

As you've noted, your engine reached normal temperatures, which would also imply that it has reached normal pressure as well.

When you removed the cap, the previously-pressurized coolant system was subjected to a rapid reduction of pressure. This very likely resulted in much of the coolant going from a liquid state to a vapor state, also known as boiling.

Your fountain of coolant is the result of the removal of the cap. There is no indication of a head gasket problem. If you begin to see milky foam in your engine oil, or oil in your coolant (check when cold) you may have that concern.

  • 1
    It is worth stating that removing the cap while at operating temperature is extremely dangerous and injury could occur.
    – CharlieRB
    Mar 30, 2018 at 12:00
  • Also, if you can see inside of the radiator itself, start it up and look inside you radiator. A lot of times you can see bubbles of exhaust gas come up through your radiator if you have a blown head gasket. Just make sure it is cold when you remove the cap to take a look... ;p Mar 30, 2018 at 19:54

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