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How to Buy a Used RX-7By Rob RobinetteA Word about 3rd Generation RX-7 ReliabilityMany people ask me about purchasing a 93-95 (3rd Gen) RX-7 as an only, daily driven car. These cars are not known for their reliability and they are absolutely scary in any amount of snow. Many, many people have had to replace their engines well before 100,000 miles. And an engine overhaul is expensive ($5000 or more with labor) because the engine must be completely removed from the car. The turbo control system is complex and prone to problems. Repair and upkeep can be expensive because the cars are rare and most Mazda dealers are not familiar with them. I've heard hundreds of horror stories from people that had minor problems that were diagnosed by their dealer as something much more expensive such as "need new turbos" when only a vacuum hose was lose, or "need a new pre-catalytic converter" when the problem had nothing to do with the exhaust.I can't really recommend a 3rd gen for someone that doesn't have the ability or desire to learn how to maintain it themselves unless you are lucky enough (and rich enough) to be near one of the rotary specialty shops (PFS, Pettit, Mostly Mazda, Rotary performance, KD Rotary, etc.)The Test DriveThere are three things you must do before you buy a used 3rd gen RX-7 (93-95). First, take a thorough test drive. Hook up a boost gauge and verify a standard 10 psi boost to 4500 rpm then a drop to around 8 psi, then 10 psi boost in second gear. It’s easy to temporarily hook up a boost gauge to the intake manifold (it has a built in nipple with a rubber cap) and then tape the gauge to the windshield.There are engine control problems that will only show up when the car is fully warmed up. Look for smooth engine operation during light throttle and full throttle acceleration. Look for a "stumble" at 3,000 RPM under light acceleration. If the car does stumble you need to realize it may be impossible to fix this problem. There are some current owners that cannot eliminate that 3,000 RPM hesitation but many others have solved the problem by improving the engine to frame and battery to frame grounds. If the car doesn't run acceptably well then don't buy it unless the owner brings it up to your standards before you buy it. Don't assume that new spark plugs or a tune-up will make the car run right.After the test drive, restart the car after about 30 minutes of cool-down. The car should start easily and the idle should quickly stabilize at around 800 RPM. If it doesn't the engine bay may be too hot and causing vapor lock in the fuel lines.The second thing you need to do before purchasing the car is have the engine compression checked. This is really the only way to determine if the engine is healthy. Many RX-7 owners have had to replace their engines around 60,000 miles so spend the money and get it tested (see the Compression Test How To).Finally, if you do buy the car see the Reliability Modifications to make the car a little more bulletproof.Rob RobinetteThinking about buying an RX-7 but have heard horror stories?By Tom JellyThe 3rd gen RX-7 is a great car, but it does have some problems. These problems by themselves are not serious in nature, but if not addressed can lead to catastrophic mechanical failures that may damage the reputation of the marquee as well as put a sizeable dent in your wallet. You must remember that this is a high performance vehicle and requires maintenance commensurate with its capabilities. I will address each item in order of importance, with the most critical items last.The RX-7 has always been a high performance sports car as each new generation was introduced. With performance often exceeding competition that was priced far in excess (or for that matter, a multiple) of its purchase price, there are some areas where sacrifices were made to save money, while developments in the high performance aspects of the vehicle were well represented. The least critical of these areas are interior trim. The black console, door and dash panels were, on the 93 cars at least, coated with material that would not hold up. Many of these early cars had these panels replaced under warranty.Some early cars also had exterior paint problems, where the color coat did not adhere properly to the primer. By now most of those cars have been touched up or completely repainted, so don't disqualify a repainted car as a candidate for purchase.The passenger door handles are very fragile, often broken and cost $250 to replace, but can be repaired relatively easily.There were 3 recalls on these cars- brakes (vacuum hose modification), new (high temp) fuel lines and cooling system (pressure cap and fan control module). These should already have been performed by now.The inadequate ground wires between the engine and body should be supplemented with heavy duty cable. In some cars this will remedy the 3000 rpm hesitation that occurs when not fully up to operating temperature.There are some vehicles with 5th gear synchro problems. The use of Redline oil should prevent the problem from developing in the first place. If not, Mostly Mazda has a spring kit that will help alleviate the problem. The 5th gear synchro may also be cracked if there is a grind every time 5th is selected.Proper (read- not too tight) belt tension is essential for water pump ($200-600) longevity. With stock cooling systems, there is a specific procedure for bleeding air from the system that must be followed when refilling or flushing.The Mazda dealer service department may be the greatest threat to these 3rd gen cars. DO NOT go to a dealer for service unless you get a recommendation FROM ANOTHER RX-7 owner first. Many dealers are not properly trained to service these cars and do more damage than repairs, but there are enough dealers and independent shops that specialize in this particular vehicle that service should not be a major problem.These cars, when fitted with just a few bolt on modifications, are capable of tremendous horsepower gains, but these modifications must not be lightly undertaken- proper fuel enrichment to accommodate intake and exhaust flow improvements MUST be provided. If you are purchasing a modified car, make sure fuel enrichment has been taken into account.Remember, for a combined total of under $600 in reliability upgrades (if you do most of the work yourself), you can have a bulletproof rotary rocket capable of embarrassing some very exotic machinery. There is no need to be afraid of the car. It just requires proper preparation, that although is not required for you basic Honda, will put a huge smile on your face when you put it through its paces. As you surf the web, take a look at the enthusiasm you see in the (many) RX-7 web sites you'll see. Racers, engineers and other technically oriented types are HIGHLY represented among the ranks of owners. People love the car for a reason, and these people wouldn't be so dedicated to the model if it wasn't so special.People keep asking me how to purge their cooling system. To purge cooing system: fill the passenger side overflow tank to the full line on the dipstick. Fill the black expansion tank near the IC to the top. fill the water pump mounted filler to the top. Start the engine and turn on the heat till it blows warm. Shut off the car and let it cool. *Remove the water pump filler cap. if the level dropped more than 1 inch, remove the cap on the black expansion tank and fill it to the top. (if less than 1 inch, fill water pump filler cap to the top, restart the car w/ heat still on, now you should be OK, just recheck every day or 2 until the level stabilizes). Replace the cap and top off the water pump filler cap. Restart the car w/ heat still on. Let it cool again. If the level drops at the water pump cap again repeat everything after * until it the level there stays within 3/4 inch from the top. If you can't get it to stay topped off after 3 iterations:Replace coolant overflow system w/ this setup: coolant_tank.htmThis should be done anyway because that little black expansion tank will split from the heat. This has caused slippery coolant to spray out under the tires and loss of control of vehicles in more than one instance. If you don't do the mod on the web page, replace the expansion tank anyway with the one from Pettit (approx. $135) to enhance reliability. If you still loose coolant, CAREFULLY check the hose from the black expansion tank to the coolant recovery tank near the air filter. Even a tiny pinhole or bad seal on this hose will prevent coolant from being siphoned back into the engine on shutdown, which will eventually lower the level of coolant in the engine. If everything still checks out, have the cooling system pressure checked and the spark plugs and oil checked for coolant- you may have a more serious problem.Tom JellyShopping AroundWhen looking for a used Rx-7, it is especially necessary to be patient and discriminating. Do not be surprised if you look at a dozen RX-7's before finding a good example. When it comes to mileage, the lower the better. There are far too many ways for careless owners to abuse and neglect the rx7. Oil changes should have been conducted regularly at every 3,000 miles or less. The car must never have overheated in any circumstance. Further, there are many examples of used rx7s on the market that have been "ruthlessly thrashed" on the race circuit or damaged by an unexpected off road excursion. There are three recall notices that must be done to any perspective rx7 is not completed already. The first is a coolant recall which replaces parts of the cooling system (water pump seal, thermostat gasket, upper radiator hose, etc.) with stronger and more heat resistant materials. The second recall involves the braking system and replaces a check valve and hose leading to the brake booster. Without this simple recall, the valve may stick under certain conditions and hinder power-assisted braking. The third and final notice that will need to be taken care of is the fuel system recall which replaces certain fuel lines under the intake manifold with lines made from material more resilient to the extremely high levels of under-hood heat associated with rotary-powered vehicles. One can also call Mazda's Custom Service line at (800) 222 5500. With the vehicle's VIN, they will be able to determine which , if any, recalls have been applied to the particular car. Unperformed recalls can be taken care of, free of charge, by any Mazda dealership.There are a few more problems typically associated with the early third generation RX-7's. Most apparent is Mazda's less-than-perfect painting process. Premature paint chipping is usually isolated to the car's hood and the rocker panels aft of the rear wheels. This problem was eventually solved when a more traditional panting technique was applied at the factory. Another aesthetically challenged area of interest is the RX-7's plastic interior that has been known to peel terribly over time. This problem was likewise fixed by the factory. Finally, when shutting the drivers side door, don't be surprised if it takes a good slam to close fully. The doors on RX-7s are notorious for their high effort requirements. Then again, anyone to weak to operate the door on a high performance sports car is too [much of a pussy] drive one, 'nuff said The Test Drive. Perhaps the most revealing analysis of the RX-7 will be conducted during the test drive. If the car is started when cold, the engine should immediately jump to 3000 rpm. Mazda refers to this function as the "accelerated Warm-up system". You should think of it as cruel and unusual punishment. Gently 'blipping' the throttle should drop the engine speed to 1500 rpm. After a few minutes of conservative driving, the idle should settle between 750 and 950 rpm. If the car has very low mileage (less than 20,000) the engine may idle slightly higher due to a "mileage switch" that is activated during the extended break-in period., Another unusual quirk of the car is a noticeable fuel-related hesitation at 3,000 rpm when the engine is cold. This is completely normal and should lessen dramatically as the car warms up. It is also very important to remember that with rotaries, like conventional piston engines, most internal wear and tear occurs during cold operation. During this time, it is absolutely imperative that driving at high rpm or under boost should be avoided at all costs. Once the car is up to operating temperatures, the real evaluation begins. Unfortunately, a stock RX7 is not equipped with a boost gauge making boost testing more of a "seat of the pants" experience. It may not be too unreasonable to bring a boost gauge and vacuum line and tap it into the small nipple on the passenger side of the intake manifold before the test drive. The vacuum line could then be fed under the hood and through the window to the gauge that can be taped to the dashTo check the boost pattern, cruise in 3rd gear at 35. As the road ahead clears, accelerate under wide open throttle. Boost levels should quickly spool to 10 to 12 psi. Just above 4500 rpm, the boost level should drop briefly to approximately 8 psi and then slowly build up to 10 psi by redline. If boost levels are unusually low or erratic, there could be problems with the complicated turbo control system of the turbos themselves. Listen carefully for knock under prolonged boost [heh heh]. Knock can be caused by running inexpensive, low octane gas or by lean run conditions caused by clogged injector or dirty fuel filters. If detonation is detected, lift off the throttle immediately and look for cars elsewhere. In a rotary, if you hear a knock, the motor is already likely to be damaged. A characteristic common with rotaries is their lack of low end torque. If the engine speed drops below 2k, the car is essentially crippled. However, right around 2500, the turbos quickly come to life and things start to happen,, Upon first drives, the car may feel "jumpy" when tooled about around town. Eventually, the driver will get used accustomed to the unique throttle management required by the power plant. RX-7s are also known to exhibit a chronic hood latch squeak that can drive some owners into fits of frustration. This noise can be fixed easily, as we will see in this project series. Clunking noises from the suspension, on the other hand, are not so readily ameliorated. Cars manufactured before May 31, 92 (check drivers side door jam) come equipped with an annoyingly noisy upper a-arm bushing. This can be replaced with an updated version, but at a remarkably high labor cost. The trans should shift precisely and smoothly. It is not uncommon for rx7s to develop 5th gear synchro damage, typically cause by a botched 2nd to 3rd gear shift. If damage is present, shifting quickly from third to 5th gear (without letting the engine speed reduce) will result in a terrible grinding sound. Repairing a 5th gear synchro is very expensive since it involves removing and disassembling the tranny. Finally, check for warped rotors, cracked wheels, engine leaks and the typical areas involved when inspecting a used car. whew,.. ohh dangit, L there's more It is also a good idea to check the water temp gauge toward the end of the test drive,. The needle should point slightly below the middle temp range., Also critical to the longevity of the motor and turbo is a nice cool down period of at least thirty seconds. Spirited driving on the track can require up to 5 minutes of cool down to let the iron and aluminum components of the engine recover from their thermal expansions. It is also normal to hear the boiling and bubbling sounds from the engine after the ignition has been turned off. |
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