Mazda RX8 13B Renesis Engine Problems
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The 5 Most Common Mazda RX-8 13B Engine Problems

Jake Mayock

Meet Jake

Jake is a founder of 8020 Media and TuningPro. He has over a decade of experience in the automotive industry including parts sales, writing, DIY modifications & repairs, and more. Jake is currently converting his N54 to a single turbo and building a Miata track car. He’s an experienced, hands-on automotive enthusiast who delivers in-depth, well-researched content.

The RX-8 and its 13B motor somehow won international engine of the year back in 2003. This was obviously before it had been on the market long enough for all of its problems to arise. Overall, the engine fell far short of the 13B-REW predecessor.

I had the joy of owning a 2007 RX-8 for about eight years. I loved the car – it was a ton of fun to drive, the handling was impeccable, but it gave me its fair share of problems. Unfortunately, these engines very rarely break 100k before failing. In this guide I’m going to cover all of the common problems with the RX8 and share my personal take on reliability after owning one.

Mazda RX8 13B Renesis Engine Problems

Mazda Rx-8 13B Engine Problems

  • Leaking Apex Seals
  • Ignition Coil Failure
  • Engine Flooding
  • Catalytic Converter Failure
  • Starter Failure
  • Excessive Oil consumption
  • Clutch Master & Slave Cylinder Failure

1. Leaking Apex Seals

Apex seals are the weakest link of the 13B RX-8 engine. The 13B rotary engine consists of two rotors which are shaped like rounded triangles. These rotors spin within a rotor housing that is oval shaped. The only parts of the rotors that come into contact with the housing is the 3 ends of the triangle. These are called the apex points and each point has an apex seal which is responsible for keeping compression within the combustion chamber.

The seals are use a spring which pushes them outwards against the rotor housing. Because the seals are metal and so is the housing, the seals are lubricated with oil to prevent internal damage.

2. Ignition Coil Failure

Likely the least worrisome problem on the list, the Rx-8 is known to eat up ignition coils. The Rx-8 uses a coil-near-plug ignition system in which the ignition coils sit grouped together and are connected to the spark plugs via spark plug wires.

Ignition coils usually fire every other RPM on piston engines. On rotary engines they fire every RPM. When you factor in a 9,000rpm redline, the ignition coils are firing so much more frequently than they are on piston engines. Ignition coils are electrical components and therefore naturally wear down over time. As they wear down they lose their ability to convert the electrical currents into the voltage levels necessary for the spark plugs to fire.

Ignition coils on the Rx-8 usually fail every 30,000 miles. When you replace the ignition coils it is also recommended to replace the wires and the spark plugs. Fortunately, a set of OEM replacements isn’t too expensive nowadays and replacing these components is an easy DIY.

3. Engine Flooding Problems

Driving your Rx8 through flood water is highly unadvised. However, engine flooding has nothing to do with outside water getting into the engine.

The cold start cycle on these rotary engines consists of the injectors dumping a lot of fuel into the combustion chamber while simultaneously feeding additional oxygen into the recirculating exhaust gases to further burn the exhaust gases and heat the catalytic converter up faster.

Flooding occurs when you shut the engine off too soon into its cold start cycle. Always warm your 13B rotary engine up before turning it off. By letting it warm up you can ensure that the excess fuel being poured into the combustion chamber is fully burned before the engine is turned off.

4. Catalytic Converter Failure

The catalytic converter fails a lot on the RX8. It however is less of an issue with the cat and more so an issue with bad spark plugs, spark plug wires, and ignition coils. When these components fail they result in extra fuel being dumped into the exhaust system which burns up the cat, clogging it.

When this happens, the melted metals inside the cat clog up the exhaust system creating a ton of back-pressure in the exhaust system. With this much back pressure the engine struggles to produce power and rev. Therefore the most common sign of a bad cat on the Rx8 is struggles revving the engine past a certain level. Usually it will start not revving past say 8,000rpms and then it will quickly deteriorate until it no longer revs above 4,000.

5. Starter Problems

The starter in the RX-8 is extremely poor at starting the car in cold weather. The ignition system is also poor in colder weather which causes the already weak starter to have to crank longer to get the engine going.

Mazda simply used a bad starter motor for these engines. While there was an early recall in 2006 and the motors were changed thereafter, older vehicles are still prone to this problem, albeit less commonly than the 2004-2006 models. Bad starter, bad ignition system = failed starter motor.

6) Other Problems

The RX8 isn’t an easy car to maintain. Taking proper care of it is essential to longevity. While the major problems with the 13B engine are listed above, I wanted to highlight a number of other problems that I ran into on mine:

Oil Consumption

While oil consumption in a piston engine usually isn’t a good sign, it’s completely normal on the 13B. Because the apex seals need to be oiled, oil naturally burns off as the engine rotates.

If you have leaking apex seals you could see increased oil usage but it is not uncommon to need to add 1 quart of oil every 1,000-1,500 miles. You need to be absolutely aware of this as a rotary owner as low oil levels can cause apex seal failure. Keep a quart or two of oil in your trunk at all times.

Clutch Master & Slave Cylinder

For whatever reason, the clutch on manual RX8’s is problematic. The slave cylinder and master cylinder fail frequently. Over 5 years of ownership and 50,000 miles, these parts went out on me twice. The most noticeable sign is that the clutch is extremely soft or easy to push in. Getting the clutch to catch becomes a total pain which leads to grinding a lot of gears.

Manual Transmission Synchros

Manual transmissions have gear synchronizers which adjust the speed shaft so that the collar and gear synchronize their speeds before the engine reengages the transmission. The synchros notoriously fail on manual Rx8’s which will cause you to grind a lot of gears.

Synchro’s most frequently go bad from over shifting or pulling/pushing the shift knob too hard or far into gear. The best $75 investment you can make is buying a synchro saver which prevents you from putting the shifter too far into gear.

Maintenance Requirements

Always keep the oil levels high enough. Keep a quart in your trunk and top the oil off every 1,000-1,500 miles. Change the oil every 5,000 miles (at most) religiously. Don’t let the engine overheat and don’t let it get low on oil.

And my favorite: a redline a day keeps the mechanic awaySeriously, redlining these engines is good for them as it helps wipe away any carbon buildup.

Mazda RX8 Reliability

Unfortunately, the 13B engine is extremely unreliable. However, most of the RX-8 reliability problems are due to poor maintenance. That said, most of these engines will start to lose compression by the 100,000 mile mark because of the apex seals.

Complete engine failure is not uncommon at the 80,000 mile mark either if the engine was poorly maintained. Even on a meticulously maintained 13B you are probably lucky to hit 125,000 miles before the engine needs a rebuild.

In addition to the likelihood of complete failure, the starters, ignition coils, spark plugs and wires, clutch cylinders, and catalytic converters fail frequently. During my years of RX-8 ownership, I also ran into a handful of ancillary problems like broken door locks, waterlogged headlights, grinding synchro’s, sway bar end link failure, among other random problems.

The RX8 is a fun car to own and drive but in todays day and age I would not expect to find a reliable one that doesn’t have a fresh rebuild. All of this goes to show why these cars can be purchased for half the cost of an early 90’s Miata with double the mileage.

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7 Comments

  1. Good article. I have been running an 05 RX8 for 4 years now (summers only) and found it to be reliable but it needs attention. So far I have replaced the crank sensor, starter, and plugs (coil wires were done just before I bought it). The car is a blast to drive and I plan on keeping it for a while yet.

    Jeremy Stiles
    Prince Edward Island

  2. Hello Jake

    What in your experience could make a RX8 with 85000km give these symptoms one after the order.
    – Car started with difficulty, then started jerking and went off
    – Grinding noise during crank
    – Starter engages but won’t crank
    – Engine won’t crank at all now

    But when the starter was disconnected from the engine and tested, it spinned.

    Plus the newly changed oil now look black

    1. Hey Andre – my initial thought would be a bad battery lead connection, if not the starter. Have you confirmed that the battery and all connections are good? This wouldn’t cause any grinding during start, but it certainly could cause a no start. The grinding noise sounds like a starter issue to me, it could be that your starter is still alive but really weak. It’s possible that it could spin when disconnected but not have enough juice to spin the flywheel. Alternatively, if the solenoid is bad its possible it could still spin but not be able to engage the pinion on the starter with the flywheel.

      Let me know if you find anything else out, but all things point to the starter to me. Also check fuses and make sure you don’t have any bad ignition-related fuses or relays.

  3. I have my second rx8 ..let’s start with the first one brand new 7 miles after about 30,000 i received a notice from Mazda corp. stating i need a recall done even Tho i had no issues of flooding (i always warmed the engine and revved before shut down)so after they did there so called tune my engine was never the same at all it blew or locked up on the way to work(i don’t dog my cars) they replaced the engine only to fail again. Being more than just ticked off i had it towed to a different dealer and told the service manager and his top rotary tech please put the computer back the way the factory had it since i had no issues at all. Well, the third engine was perfect, and the tech told me he returned the OEM specs. sad to say after only 1,000 miles a drunk driver totaled my belove 8 it flips upside down. lucky I was not hurt at all except for my feelings into the car. I waited four years and finally bought a used rx8 with 66400 on the clock I’ve noticed the engine has been replaced but several 10mm bolts missing here and there. done all my own repairs and tune, oil changes. I work at a dealer. had tech put in a clutch flywheel and all the reg stuff for a complete job he left the bolts loose on the pressure plate and boom now i need a new starter and transmission!!so lesson learned i will be doing the complete job myself…i love my 8 and i just won’t have anyone work on it again. Live in Virginia waiting on trans from Florida. Sorry about the long story don’t let anyone but a pro touch your beloved 8!!!

  4. RX-8 2006. Is it safe to use INJUCTOR CLEANER (Lucas upper cylinder lubricant ) in this engine ?
    Thanks; Bill H.
    P.S: Vary informative articles onthe RX-8 Engine.

    1. Yepp, any injector cleaner is safe. Sea foam is probably the best. But glad you enjoyed it! I owned my RX-8 for 7 years before moving on from it but am gonna have to pick another one up at some point for fun.

      1. My RX-8 has the SHANKA SPORT UP GRADE. I KNOW ABOUT THE UP GRADE FOR BUSHINGS AND SHOCKS. Are the brake pads, front & rear different from a regular RX-8 ?

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