[viperover]

When you mention blowing the pipe would that be bursting or comming off the aaly pipe.

Fluctuating temp gauge is not a good sign indeed but firstly I would replace the sender unit before I possibly mention the dreaded head gasket issue, when thermostat was replaced previously did it over heat then.

Sounds like you have a blen motor failure on the climate control system..

 

[viperover]

Sender unit is a sensor that measures, in this case the temp of the coolant, it sends information to your dash cluster informing you via a gauge how hot the coolant is.

you say pipe is bursting, unless its a bad batch of pipes which I doubt seems you may a problem

 

[viperover]

Removing spark plugs can most of the time show which cylinder is problematic by looking a lot cleaner, like new compared to the rest of them