Is it more cost effective to buy a new car?

12 year old car with above average miles,probably has the auto transmission. If you pull the pan and timing cover you might as well do the timing chain,possibly new main seals and oil pump,service the tranny....by the time your mechanic gets done he'll be thanking you for paying for his new boat. Not sure what you may have done during the years for other repairs/maintenance but if you haven't rebuilt the tranny,got new drive axles/CVs,new struts and shocks then they vehicle is going to turn into a money pit if you can't do the work yourself. I would find comparable vehicles on CL within 500 miles of you and price your Mazda at about 85-90 % of the average price you find;the vehicle has served your needs,and while I can't say I like car payments,at least they are same every month and not $500,then $900,then $1200 to fix the next thing(s) that breaks.

ANY cover is more than likely available at a salvage yard.

There are THREE numbers to consider when answering your question.

1. How much can you sell the vehicle for AS IS?

2. How much will it cost to repair the vehicle?

3. How much will the vehicle be worth after repair?

If the total of 1. and 3. is greater than 3. it is time to replace the vehicle.

I check the OBD II emission system with my scan tool & its at yellow, but no codes.

That literally CAN'T be true. OBD II scanners don't report a color. Either there ARE codes, or there is NOTHING.

That depends on the book value of your present car, how much the repairs to it will cost, and how reliable it is outside of this breakdown.

And, you could buy a new-to-you used car, which would be cheaper than a new car.

With that problem and that many miles I think it would make a good 'Mechanic's Special' on Craig's List.

In all likelihood the cost of the repair will far surpass the current value of your Mazda. Time to send it to the crusher.

YES ITS TIME TO SEE IF YOUR BANK ACCOUNT ,LETS YOU UPGRADE ,IT DOES NOT HAVE TO BE NEW BUT A 2 YEAR OLD CAR WILL DO FINE