Mazda RX7 13B REW Engine Problems

5 Most Common Mazda 13B REW 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.

I owned an RX-8 for years, but man I always wished it was an FD RX-7. With sequential turbocharging and a rotary design, the 13B-REW was a lot more capable performance wise than its successor. It was more reliable too, but rotary engines aren’t well known for their reliability or longevity. While the 13B in the RX-7 was a bit stronger, it still suffered from a lot of problems and premature engine failure.

The RX-7 is prone to apex seal failure and low compression, bad catalytic converters, cracked turbo manifolds, various wiring and hose failures, and a tough maintenance schedule. We’re going to discuss each of these problems in depth below and discuss how to take the 13B-REW engine beyond 150,000 miles.

Mazda RX-7 13B Common Engine Problems

  • Apex Seals & Low Engine Compression
  • Catalytic Converter Failure
  • Vacuum, Radiator Hoses, and Wiring Harness
  • Rigorous Maintenance Requirements
  • Cracked Turbo Manifolds

1. Leaking Apex Seals

To keep compression high, the three triangle tips of the rotors must keep an airtight seal in the housing. Each corner of the triangle has a seal, called an apex seal, that is pushed against the rotor housing with a spring to form the airtight connection. Apex seals are generally made of metal, and because the housing is also metal, the seals need to be lubricated with oil.

On the FD RX-7, the apex seals are one of the most common ‘engine killers’. Because the seals require constant oil, the 13B actually consumes oil in excess of traditional engines. Therefore, additional oil usually needs to be added every few months.

Both excessive heat from the engine and a lack of oil can cause the apex seals to become worn or cracked. When this happens, the seals lose their airtight connection and the engine loses compression.

Symptoms of Bad Apex Seals

  • Rough idling
  • Engine shuts off during idle
  • Misfires
  • Big power loss and lack of acceleration

2. Catalytic Converter Problems

The 13B REW uses two catalytic converters. The first cat is located within the downpipe, and the second “main” unit is located after it. Because the sequential twin-turbo system generates a lot of engine heat, the first catalytic converter is prone to burning up and clogging up the main catalytic converter.

When this happens, the exhaust air flow becomes restricted, pushing the air back into the engine and causing engine temps and exhaust gas temps (EGT’s) to skyrocket.

The most noticeable symptom of a clogged main cat is excessive EGT’s. As this causes internal engine temps to increase, it can have catastrophic damage on the engines internals and the apex seals leading to total engine failure. The best option for preventing this issue is to install a catless downpipe on your FD RX-7. While this can create issues passing emissions tests, removing the cat will improve exhaust air flow and actually lower internal engine temps which will prolong the life of your 13B.

3.  Vacuum, Radiator Hoses, and Wiring Harness Failure

While the 13B REW is generally a small engine, it is also crowded into a pretty small engine bay. Because of the excess heat that the sequential turbo system produces, the temperatures within the engine bay are also very high. The excessive heat causes a number of frequent failure points across various hoses and wires located within the engine bay. Failure of these parts can cause electrical malfunction, boost leaks, engine overheating, and a number of other potentially dangerous problems.

Vacuum Hoses

Vacuum hoses must maintain internal pressure to function properly. The excessive engine heat can cause these hoses to harden and crack. When this happens, air can leak from the hoses, reducing pressure and causing a loss of power and overall performance. We recommend replacing all vacuum hoses with wrapped silicone hoses which can withstand much higher temperatures. The materials are super cheap but it is a rather labor intensive job, requiring 5-6 hours of work.

Radiator Hoses / Expansion Tank

The 13B’s radiator and coolant hoses, especially the ones that connect to the turbos, are also prone to warping and cracking. Additionally, there is a radiator/coolant expansion tank that is prone to failing. We recommend replacing the coolant hoses with high temperature silicon hoses. Also, there is a simple $30 modification that will completely remove the expansion tank and therefore prevent it from failing.

Wiring Harness

Again with the excessive heat, the wiring harness can also make the wiring harness brittle and prone to failure. When this happens, it will cause a number of electrical problems.

4. Turbo Manifold Problems

The 13B REW turbo manifold, or exhaust manifold, connects the turbochargers to the exhaust system and passes air out through the exhaust system. Rotary engines, like all other traditional engines, experiences heat cycles. Heat cycles are simply the heating and then cooling of engine components and occurs when you warm an engine up and them turn it off and let it cool down.

The turbo manifold is made of metal, and metal expands under heat and contracts when cold. The constant expanding and contracting in conjunction with being connected to the vibrations of the engine cause the manifold to develop cracks in the metal. These cracks can either be small hairline cracks or larger, noticeable cracks.

Small hairline cracks likely won’t cause a very noticeable performance decrease, but once a crack exists it will continue to deteriorate. Once a larger crack forms, air will begin to slip out of the cracks and therefore reduce pressure within the engine. When pressure reduces, turbochargers become less efficient and have to work harder to produce the same amounts of power. Ultimately this puts added stress on the turbos, which can cause them to fail, and will also cause power loss.

Cracked Turbo/Exhaust Manifold Symptoms

  • Low boost, lack of ability to produce boost
  • Lack of acceleration, loss of power
  • Exhaust smells inside of the cabin
  • Whining or whistling sound from the engine

5. 13B-REW Rigorous Maintenance Requirements

While this isn’t necessarily an engine problem in itself, it does cause a lot of engine problems. These engines require proper maintenance and care. The majority of catastrophic failures with these engines are caused by owners who are not responsible or aware of the requirements of owning a rotary engine powered car.

While you should follow the recommended maintenance schedules, here are a few important items to keep in mind:

  • Add 1qt of oil every ~2,000 miles
  • Change the oil and filter every 3,000 miles
  • Only use non-synthetic oil
  • Never shut the engine off when it’s cold
  • A redline a day keeps the mechanic away (seriously, redlining it is good for the engine)
  • Prevent overheating

Heat is the killer of these engines. There are a handful of cooling system modifications that can be made for under $100 that can drastically improve the reliability of these engines. Check out the link in the next section for a detailed list of cooling mods.

Mazda FD RX-7 & 13B REW Reliability

The 13B REW can be a reliable engine. However, these engines were never made to be 300,000 mile cars. They require special attention and are not the cheapest cars in the world to maintain.

On a poorly maintained engine, expect to rebuild it by the 80,000 mile mark. For meticulously maintained engines, you can likely get beyond 120,000 miles before a rebuild is needed. The biggest killer of these engines is excessive heat. We recommend cooling system upgrades such as an aftermarket radiator, dual oil coolers, etc. Here is an awesome guide on 13B REW Cooling Upgrades.

With all that being said, these engines have a finite lifespan. Reaching the 150,000 mile mark without any major issues is possible if properly maintained. However, a majority of these engines will fail before that period, and if they do make it that far, they likely don’t have much left in them. Maintain the engine as if you want it to last forever, but understand that a complete rebuild will be a necessity at some point during the 13B REW’s life.

Upgrade the cooling system, replace the vacuum and radiator hoses, remove the downpipe catalytic converter, keep the engine well lubricated with oil, and follow the recommended maintenance schedule and the 13B REW will be bulletproof.

As far as the engine and its internals, the 13B REW can handle up to 700whp without any internal modifications necessary. The stock turbos are solid but they are generally capped at about 350whp and 15psi of boost. If you want to produce power beyond those levels, an upgraded set (or single turbo) will be required.

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One Comment

  1. Good and useful information. I have a 1994 RX7 that went into a dealership to have hoses to the turbos an engine replaced. The car came back running great but there is additional noise from acceleration over the normal engine noise. The dealer refuses to answer my questions about why saying they do not work on 1994 RX7s. My next stop will be Mazda USA then a lawyer.

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