Like most of the people in HK I don't have a garage so I can only do limited DIY. Tool is not an issue as the next door to China mean lot of cheap tools. If you wonder the quality I would say "what you pay is what you get".
I can easily duplicate the situation by driving around for 10 min to heat up the coolant. I sent it to my usual indy today and explain to him one of the possibility is the expansion of old hose under pressure. However, he pointed out to me when the hose get old it get harder
. So, old hose under pressure most likely crack instead of expand.
He called me few minute ago said found leak in the transmission oil cooler. I think a leaking transmission oil cooler would mean just lost coolant but not going have what I am experiencing. Unless the coolant would go into transmission oil and when the pressure release the coolant get push back up from the transmission cooler.