COOLANT CAP FULL

If a lot of gas escapes before it comes out as steady liquid, that’s a strong sign that there is a high pressure fire ring leak.

COOLANT CAP FULL

If, after driving awhile at full operating temp and before cooling down, the reserve tank level has been seen to rise substantially and the pressure tank liquid level is visibly low (this is what triggers the Vanagon low coolant warning flashing LED, and on earlier vans the temp needle will also peg high), then remove the front grille and crack open the radiator bleeder bolt while the engine is still warm. But such a large leak would almost never be seen in real life because long before it reached such a state the engine would have become practically unusable due to the dynamics explained in the next section.Ģ.

Such a leak would be obvious on a leakdown test, and would be big enough to allow coolant to be forced into the cylinder after shutdown, which would cause the spark plug to look very clean, if one were to look, or could even push enough liquid in to cause hydro-lock on the next starting attempt. If it were a fire ring leak and it was able to produce gas bubbles at the very low in-cylinder pressures when idling, the leak would have to be a big one. The same engine was leakdown tested as having excellent combustion containment. Installing a cap that bench tested as holding the specified 1 bar made the bubbles stop. The pressure cap doesn’t have to be failed wide open for this phenomenon to occur, I have seen bubbles rising in the pressure tank at hot idle with a cap that was still holding 6-7psi.

Coolant cap