Mazda Forum - Mazda Enthusiast Forums - 2008 Mazda 3 1.6L MZ-CD cylinder head gasket

Hello everyone,

I have a 2008 Mazda 3 1,6L MZ-CD and I have been having problems with the coolant system. The coolant is turning black but it doesn't seem to be oil.
I have drained the coolant and flushed the system and now have been filling with only distilled water to test the system and after a short drive, the water turns a dark color looks like dirty water not oil.
There also seems to be a leak somewhere because the level drops but extremely slow though.
I haven't had any problem with the temperature of the motor, but I am having problems with the hot air through.
It is a bit unstable, as I drive with the hot air at max it fluctuates a bit. Sometimes warm and sometimes colder but not how it used to work. Before with max heat, the air was always very hot.
I haven't noticed any white smoke coming from the exhaust.
I have an OBD reader and the coolant temperature is always around 68°C-72°C with the motor warm and driving.

So my conclusion is that the is a problem in the cylinder head gasket that is letting the coolant come in contact with exhaust gases causing the dark color.
Since this is an expensive bill if I go to a mechanic, I am going to but the gasket on Ebay and try to change it myself. I have most of the tools I need but I am unsure of the cylinder head bolts.
I have the repair manuals for the model I have but it doesn't say what type of bolt is used, and before I start taking thing apart I want to make sure I have all the tools.
Does anyone know what type of bolts is used?

Thanks for the help