Howdy , I bought a 97 Tarago.About 2mnths after, had to replace head gasket. recently it ,(only at intersections)the revs started to drop.Nearly to the point of stalling. Took it to my mechanic and we took the idler assembly out and cleaned it.Refilled with water but,Now water is spurting from the overflow tank.Water Level drops, We refill it and it does it again.Water temp is perfect,Oil is perfect,It has got me stumped. Has anybody please got any suggestions.Muchly appreciated