Radiator water temp needle - query For my vehicle Diesel Punto, i got done my second year 30,000km service done recently. Post taking delivery, after a cold Start, the pattern in which the Radiator Water temp needle rises up to optimal operating temperature has changed. 1. I am realizing that, post delivery the radiator water temp needle is climbing to operating temp (Dot center) earlier than originally it used to rise. I gauged this with pre defined distance which i am aware after a cold start, Why this change in behavior ?? 2. Unable to conclude, i checked for coolant leaks and visible spots in engine bay, All i could see was the coolant level during engine operation was at the low mark. After 30 mins of turning off the engine i opened the cap. 3. There was a release in pressure and some more coolant returned back to the reservoir there by increasing the coolant level now. Could this be vaccum or air lock as a result of which coolant was not flowing through the critical systems freely ? How much tight should i secure the cap ? 4.I was told in the affirmative by the service advisor that the coolant topped was a pre mix one and does not need any distilled water top ups. As a result of that pre mix top up the coolant is bright pink as against light pink earlier? Will pre mix coolant alone not harm the engine, acc to me some amount of distilled water top up is mandatory ? pl clarify.