I have had my 2006 automatic RX8 w/ approximately 90,000 miles since November of 2015 with no issues. A few days ago, I was driving on the highway, not even pushing my RPM'sand was doing 80-90 at the most when I felt as if the car rapidly downshifted itself 2-3 gears. After this happened, it seemed fine and it was running fine, despite me babying it to the closest gas station. After pulling in and checking out my engine, it was quite clear it had somehow overheated without me even noticing. I checked my coolant immediately and even went into the gas station to get distilled water hoping to god that I didn't damage my rotary. I didn't notice any damage to my cooling tank or anything of that nature but the coolant indicator still remained on and the engine would not start.

I had it towed to my normal mechanic who also worked on my 3 series BMW and they have always been loyal and 100% straight with me. The next day, I was told what I feared; the engine had overheated, there was a crack in my cooling cap and I was told I needed a new engine -- Any time they tried adding water to the tank and starting it via the plugs the water spurts everywhere on them. I don't even know if it can be rebuilt. So I was told I'm looking at about 3 grand in total with labor and that I can get a new engine with 74,000 miles for $2050.


I literally just had it serviced there too a few days prior for a new tire and oil change which they claim has nothing to do with it. At this point I honestly have no idea what to do and what could of caused this. My coolant light never came on to tell me anything whilst driving and I checked the coolant level manually earlier in the week. Why did my engine overheat like this when I literally had done nothing to even push it to overheating. How screwed am I? Can the engine be rebuilt? I just wanted to get a few other opinions on here on what could of possibly happened.

Thanks in advance.

 

I would not bother with a used engine, it's too risky. Either contact a reputable rebuilder (pineapple racing, rotary resurrection, etc) or get a reman from Mazda. But really it comes down to what the car is worth to you because a proper rebuild and install will cost more than the car is worth resale wise.

 

Where does the water "spurt" from?

You could just need a new coolant tank, which is a common point of failure. If it is spurting from the top side, it might be the coolant tank or a hose or fitting. The radiator has plastic tanks, which are also known to crack.

If it [the overheating episode] was really bad, you could have blown an engine seal, which means you would be losing coolant under the engine. This is similar to blowing a head gasket in a piston engine, but not as cheap or easy to fix.

 

Damn. I'm so sorry bro. You could've avoided this if you kept an eye on the coolant temp gauge. And yes, the coolant tank neck is known to crack. A similar thing happened to a friend of mine last year. He was also doing about 90mph on the highway and he saw the coolant temp gauge go up. He didn't pull over ASAP because it wasn't in the red zone, but he did about 5 minutes later. As he was coming to a stop, the car died on him. Turned out the coolant tank neck had broken. We tried to start it but it didn't start. Whenever it cranked, coolant shot up from the radiator cap. Car went home in a tow truck and he got the engine rebuilt.

I'm guessing that's what happened to you. Coolant bottle neck snapped, coolant lost pressure and quickly boiled over, spilling most of it out of the tank neck. Running an engine with little to no coolant = disaster.

**** happens. When you get the engine replaced or rebuilt, make sure to get a coolant temp gauge. That will tell you if somethings wrong, way before it damages the car.

Stay strong man.