From online research, and talking to the mechanics at the Mazda Firm, I have to conclude that there is a small crack in my engine head.

. It is very small, so I have a few things that I am currently trying at this moment (and there are signs of it working).
I never changed my engine's thermostat (and I'm doing 180,000km currently, shame on me) and I believe it's sort of sticking in the open position (which is lucky for me). The temperature sensor in the HUD fluctuates up and down,
below the nominal engine temperature, hence the reason why I say it's sticking in the open position, else it would have started to overheat. Still doesn't explain why the head got a crack if the engine is running cooler than normal. Guess the temperature fluctuation caused rapid expansion and contraction causing the crack to form (I could, and probably am wrong with that theory). Whatever, the head is cracked. He is what I'm currently using to stop the problem:


Bar's Leaks - Block Seal Head Gasket Repair. Bought on Cipero Street, San Fernando, in Sherif's Automotive (Opposite Triple R electronics, near Republic Bank) for somewhere around $75 (can't remember exactly

). WARNING : PLEASE READ THE INSTRUCTIONS CAREFULLY BEFORE USING.
Currently, Mazda firm does not have engine thermostat for the van (priced at $175). They should be getting early March. Was also told from a friend that Ford doesn't have any at the moment either. So I bought an after market one ($135, on Cipero Street. The place is called (can't remember the spelling, Guya's. Again, it is next to Triple R Electronics). The brand is ummmm.... this:

Now to use it. To drain the engine and flush ALL the coolant out of the system, I took off the inlet water hose to the radiator (the one at the base of the radiator) and took out the thermostat. Got this from the Mazda manual for those who need it:


If you simply follow the inlet hose from the radiator back to the engine, you will find the thermostat housing very easy.

I simply not pushed a garden hose into the inlet hose of the radiator and sort of sealed it using my hand. The water filled up the radiator and pushed all the coolant (at least I hope so) out of the engine. I let it flow through for a good 5 minutes as I heard that coolant mixing with the stop leak can cause clogging. After, I put back in the
OLD thermostat and assembled the engine (why add the new thermostat and run the stop leak through it if your old one still works?) The stop leak is a dense fluid with something resembling sand in it. Didn't want to use my good thermostat with that flowing through it. Follow the instructions on the stop leak carefully and hope it works.
Oh, the instructions say use the entire bottle for big engines, and half the bottle for 4 cylinder engines with no A/C. So I ended up using 3/4 of the stop leak.
Also, this is what my old thermostat looked like:

I scraped off the build up of that green sediment thingy with a small screwdriver. Can't remember what it's called at the moment. I am currently at step 10, so late tomorrow evening I will report on the results. As of right now, the hard vibrations I normally get at start up has reduced significantly after about 10 seconds of running from cold start. Before, it took like 4 minutes of idle RPM to idle normal. So that is a good sign.