Technical tips, advice and shared information.........That's what this page is all about. This is only a very small part of the tips that appear in each issue of the member magazine.
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Q: I have just purchased a 1988 Mazda RX-7 GXL with 115,000 miles on it. Most people consulted, including a dealer service manager, said the rotary engine is good for only about 100,000 miles before needing a rebuild. My engine burns no oil that I can see, including during engine braking. What are the symptoms of rotary engine failure? What can I do to keep what is now a good engine in good condition?
A: Rotary engines are inherently simple, and aside from giving them normal care, there is no special maintenance required. Of course, the easier you drive a rotary, the longer it will last, just like a piston engine.
Loss of compression past the apex or side seals is the main trouble with high-mileage rotaries, according to our research. Typically one apex seal goes, causing low compression and hard starting. Because each rotor gives three distinct compression pulses for each rotation, low compression from a bad apex seal is often heard as uneven cranking speed.
Compression testing will show poor apex seals, too. Rotary technicians favor a special, tracing compression gauge, but a standard dial indicating gauge is still useful. Hold the release valve open while testing to observe the needleís free movement, and pay special attention to comparing the results from one rotor to the second. They should give equal readings. Remember, there will be three pulses per rotor revolution. Two weak and one strong pulse are typical for a bad apex seal. Leaking side seals show as just one weak stroke and two strong ones.
On 1993 and later Mazda rotaries, any vacuum reading below 18 in. of idle vacuum is reason to suspect the rotor seals. On all rotaries, smoking through the exhaust during deceleration shows the oil consumption rings are going bad. The oil rings seal the rotors to the shaft. They are necessary because thee rotors are internally bathed in oil for cooling purposes. Also, earlier engines will blow exhaust into the cooling system when overheated, so check for bubbles in the radiator.
Q: I have a Ď91 Mazda 626 with a 5 speed tranny. I want to change the oil. I think I have 80 W gear oil in it. I am not real sure though since I gather manufacturers sometimes put Dextron II in without a dye. My owners manual says I can use Dextron II or GL 5 gear oil.
Is there a problem changing over to a synthetic Dextron II. Does all the old oil come out from the drain plug or do you have to do a few changes to get all the oil out?
A: My application book does say that either ATF or a 75 W - 90 GL-4 or GL-5 fluid is used in that transmission. It also says to "check lubricant specifications label under the hood". This would seem to indicate there may have been 2 different transmissions used in that vehicle, one using ATF and one using gear lube. See if you can find the label under the hood and then try. If they are the same, stay with it. If not, cross your fingers and go with it. I would tend to stay with what is in the transmission if you have had it for while and not had any problems.
Q: Hey guys ... I'm looking to buy a 2005 RX-8 with 26,000 miles. I hear you have to do a lot of stuff to cool down/warm up the engine before/after driving. What do you have to do exactly? The guy at the dealer said donít take a lot of short trips. What is a short trip classified as?
A: Just let the car idle for a few minutes before leaving and before turning off the car. If you just start up the car and go off, well thatís not good for the rotary engine. Same goes for cars with turbos.
Q: I just closed the deal on a 1995 Miata "M Edition". Purchasing from a Mazda dealer in Cincinnati OH. The car has 98K miles. Care is in VERY clean cosmetic condition very little wear anywhere on the interior/exterior. AC, power windows, etc. all work. It even has the original floor mats in the trunk (never used!). It has a clean CARFAX. Was originally purchased in the Cincy area and has always been a local car. Only thing I can detect might be a weak clutch. The dealer has replaced the valve cover gaskets, tune-up and drive belts (~$450 of dealer work).
Any ideas what I should check or do?
A: You mentioned drive belts. If they did not do the timing belt/water pump/tension pulleys, cam seals, CAS O-Ring and front Oil Seal, and you can't find documentation on the car showing where it was done, be ready to do that. You can do it yourself, in a weekend, if you're mechanically inclined. It's not too hard the first time, just be sure to do it all at once.
Judging from your statement that it was $450 worth of work, I am thinking they didn't do the above stuff, as most dealers would charge about twice that given the labor involved.
Timing belts are "recommended" to be changed at about 60K, some people have gone 100+K on theirs.. So no idea about yours, given what you've said.
That's more than reasonable for a Ď95 Miata, actually, especially one with 100K on it. Miata prices don't typically follow KBB unless you're buying from a dealer, or dealing with insurance... Not sure about Cincy, but at least most areas, Miatas sell for more than what the book says they should be worth, and if you find a good price one, they tend to be snapped up pretty fast.
Q: I just closed the deal on a 1995
Miata "M Edition". Purchasing from a Mazda dealer in Cincinnati OH. The car has
98K miles. Care is in VERY clean cosmetic condition very little wear anywhere on
the interior/exterior. AC, power windows, etc. all work. It even has the
original floor mats in the trunk (never used!). It has a clean CARFAX. Was
originally purchased in the Cincy area and has always been a local car. Only
thing I can detect might be a weak clutch. The dealer has replaced the valve
cover gaskets, tune-up and drive belts (~$450 of dealer work). Any ideas what I
should check or do
A: You mentioned drive belts... If they did not do the timing belt/water pump/tension pulleys, cam seals, CAS O-Ring and front Oil Seal, and you can't find documentation on the car showing where it was done, be ready to do that ... you can do it yourself, in a weekend, if you're mechanically inclined. It's not too hard the first time, just be sure to do it all at once.
Judging from your statement that it was $450 worth of work, I am thinking they didn't do the TB stuff, as most dealers would charge about twice that given the labor involved...
Timing belts are "recommended" to be changed at about 60K, some people have gone 100+K on theirs ... so no idea about yours, given what you've said.
That's more than reasonable for a 95M, actually, especially one with 100K on it. Miata prices don't typically follow KBB unless you're buying from a dealer, or dealing with insurance... Not sure about Cincy, but at least most areas, Miatas sell for more than what the book says they should be worth, and if you find a good price one, they tend to be snapped up pretty fast.
Q: Can anyone give the part number or the name of the plastic pieces that surround the radio, AC knobs and lighter in an 05 Tribute? Or tell me where to get the part?
A: You may want to look at this site https://parts.mazdaclub.com .
Q: My 1992 626 2.0 was set at high RPM (2000) at rest for years. I instructed my mechanic to lower it to improve fuel consumption when he replaced an over heated engine. The car stutters when RPM is lesser than 2000 ever since. The Mazda computer blames the distributor; that was replaced along with itís wiring, to no avail.
Please no lemon law suggestions my sister is the previous owner the one before is her friend, the mechanic is my friend.
A: I think your mechanic may be a
better friend than a mechanic
Q: Can anyone give me an idea what causes the check engine light to come on in a 2001 Protege, 2.0 engine. I have put on a new air filter, the gas cap is tight and in good shape. It has 77,110 miles on it, mainly freeway driving at 65-70 mph, 125 miles per day. It runs great!
A: If you take it in, they will tell you itís the O2 sensors (even when itís not). Iíve had a 1995 Protege, 2000 MPV, and 2006 MPV and they ALL have had problems with the check engine light. Iíve finally learned to ignore it and in a few weeks, it will go off by itself.
Power out of Dr. Wankel's Fascinating Engine
It looks like nothing else that was ever bolted to a transmissionís bell housing ó a chunky little cask made of alternating slabs of cast iron and aluminum, housing two triangle-shaped rotors that orbit an aptly named eccentric shaft. Itís otherwise known as Mazdaís Wankel engine (with the 12A variant powering our 1983 RX-7 project), and itís what makes the RX-7 the most commonly raced car in the Sports Car Club of Americaís Improved Touring A class.
Why, you ask? First, the Wankel engine itself is simpleógases move into and out of the combustion chambers through ports; no moving valve train parts mean no pushrods to bend, no rocker arms to snap, no valves to bounce off the tops of pistons. Consequently, they tend to tolerate the occasional overrev better than their reciprocating cousins. Wankels also have a reputation for longevity ó a well-maintained engine can be raced for three or four seasons without a rebuild. Letís not forget that the Wankelís handy carrying case wonít break the bank, either ó a 1979-1985 RX-7 can be found for less than $2000, almost cheaper than dirt. And heck, with the Wankelís being the winningest engine in IMSA history and a 4-rotor versionís having won at Le Mans in 1991, the rotary has the sort of competition pedigree that evokes warm images of Moet-soaked podium finishes and waving checkered flags.
With no budget for a fresh engine, weíd have to make do with our carís original 12A, a "well broken-in" example with just over 100,000 miles of service. It still ran strongly, didnít smoke much and didnít consume excessive amounts of Castrolís finest 20W-50.
There was, however, lots of oil and crud on the outside of the engine and transmission, so we thought a logical starting point would be to pull the whole mess out with a cherry-picker hoist and clean it up as much as possible with multiple cans of Gunk degreaser, a scrub brush and lots of paper towels.
That accomplished, we replaced the engineís front and rear main oil seals, the oil pan gasket and the transmissionís main seals, a move to delay repeating the entire de-crudding process for as long as possible. Seal removal and replacement is straightforward enough, prying out the old pieces with a big screwdriver and tapping the new ones in gently with a hammer; but getting access to the engineís rear seal is more complicated ó the flywheel, held on the eccentric shaft by a huge gland nut thatís torqued to about 350 lb.-ft., needs to come off. Youíll need a special wrench that looks like a Land of the Giants prop (its bar-stock handle is nearly 3 ft. long!), as well as a means of immobilizing the flywheel, to break it loose.
With sunlight now glinting off the engineís freshly scrubbed castings, we got down to the business of extracting more power in a racing class with a rather narrowly written set of rules. The largest gains are to be had with a less restrictive exhaust; to this end, Racing Beat provided us with an ideal "street port" system ($568.00 complete) consisting of a header, two pre-silencers and a Prima Flow main muffler in the stock location. Made with a 716-in. header-to-engine flange and 2.0-in.-diameter thick-walled steel tubing, this bolt-in system is designed to handle the rotaryís extreme exhaust temperatures (up to 2000 degrees Fahrenheit under full throttle and high load, versus maybe 1400 for a piston engine). And though IT class rules donít allow for power the cheap and easy way (i.e., porting), the "street port" system works very well for non-ported engines too. Key to its design are primary tubes that run nearly the length of the wheelbase, merging just before entering the main muffler at the rear. The effect here is to keep each rotorís exhaust pulses separate until the last possible moment, thereby increasing the scavenging effect and producing more power, especially at high revs. How much? Perhaps 25 bhp, bringing our total to about 125.
With exhaust fitted, our attention turned to induction, but first we removed the complicated web of emissions-control valves and vacuum lines, many of which connect to fittings in a plate at the base of the stock 4-barrel carburetor, fittings that need to be plugged with caps available at any auto parts store. The air injection pump and its associated hoses and clamps can be taken off at this time too, along with the check valve that bolts to the side of the intake manifold (the resulting hole is neatly capped with a block-off plate made by Racing Beat).
The rules permit updating and backdating of parts, and we learned that the intake manifold from a 1979-1980 RX-7 flows the best, because it lacks whatís called the "shutter valve" that helps prevent backfiring on deceleration. Willing to trade a little backfiring for better flow, we obtained a 1979 manifold from Dave Lemon of Mazdatrix, who, in addition to building street and race Wankels and offering a full line of hop-up parts, has a pretty good inventory of used spares.
For 12A RX-7s, the stock carburetor must be retained, but can be rejetted (we left the primary jets stock, but changed the secondaries from 160s to 175s, those numbers corresponding to orifice diameters measured in hundredths of a millimeter) and can be stripped of any emissions-related devices. We removed the choke butterfly and shaft to improve airflow, and plugged the resulting holes by hack sawing the shaft in two, mushrooming the ends with a hammer and reinserting each piece from the outside of the carb. A blob of silicone sealant on the shafts makes the whole setup airtight. The last internal carb change was to replace the stock needle valves in the float bowls with ball-type valves (called "Grose Jets," about $7 apiece, from Mazda Competition Parts) that are said to better maintain the fuel level under racing conditions.
With larger jets admitting more fuel, we thought the stock fuel pump (underneath the car, just ahead of the rear axle) might be overtaxed, so we installed a 6-psi Facet fuel pump ($41.00, from Racing Beat), plumbed in parallel, to ensure adequate flow. And in case this proved to be too much pressure, a Purolator fuel-pressure regulator ($15.70, from Racer Wholesale) was spliced in near the carburetor.
Capping off our carb (literally) is Racing Beatís Power Pulse air filter assembly ($50.00), made of powder-coated spun aluminum with a washable foam filter element. While this element offers no improvement in airflow over a clean, stock paper element, its flow isnít impaired by significant amounts of dirtósomething that canít be said about the stock element. And while cleaning and re-oiling the foam is a messy, disgusting job, it certainly beats buying a new paper element every two races!
Weíre down to finishing touches now. A set of low-resistance Race Ignition Wires ($93.00, from Racing Beat) adds a bit of color and undoubtedly a hotter spark, and is the only deviation from the very robust stock electronic ignition system that was introduced on the 1981 RX-7. Make sure that the cap and rotor are in good condition. For cooling, the stock radiator will suffice for IT racing, provided it is relatively corrosion-free (luckily, ours was). But youíll want to remove the thermostat and plug the water pumpís internal bypass, which we accomplished with a large-diameter bolt (hacksawed down to about 12 in. in length) and copious amounts of JB Weld, an incredibly strong 2-part epoxy/metal compound available at most auto parts stores. The cooling fan? We tossed it, knowing that above 30 mph or so, ram air dissipates more heat than the fan ever could. Weíll just have to keep an eye on the coolant-temperature gauge if we do any extended jockeying around in the pits. As a last nod to improved cooling, we replaced the stock drive pulley with a special small-diameter one (about $60, from Mazda Competition Parts), which spins both the water pump and alternator more slowly. This reduces water-pump cavitationóair whipped into the coolant, the bane of effective heat transferóat extended high rpm and frees up a bit of power as well.
So what we have is a strong-running but high-mileage 12A Wankel that is fluid-tight, clean and makes perhaps 135 bhp. To make sure it remains together for as long as possible, we installed a 10,000-rpm tachometer and oil-temperature and pressure gauges (retail priced at $131.90, $89.25 and $55.75, respectively) supplied by Auto Meter to monitor vital functions. The tach mounts to the steering column with a hose clamp and special bracket, but we went the extra mile to showcase the other gauges. Staff composites guru (aka Road Test Editor Kim Reynolds) laid up a nice sheet of carbon fiber that we trimmed, filed and drilled for a center-console gauge panel, which also houses pull-knob switches for the lights and wipers, a starter button and an electrical-system continuity lamp. The brushed-aluminum bezels and faces of the Pro-Comp Ultra-Lite-series gauges play nicely off the dark carbon fiber, making for a semi-exotic yet functional finishing touch.
As you may have deduced from this story, our RX-7, resplendent in its freshly applied, zippy paint scheme, has already sampled its first taste of racetrack, putting yours truly through SCCAís competition school at the Streets of Willow circuit near Lancaster, California. With Novice Permit in hand, Iíll keep you posted in About the Sport on how our project car fares in actual competition
The engine in my 1991 RX-7 would act as if it were going to stall and rpms
would fluctuate wildly. The dealer did not know what was causing the engine to
act this way. About a month after this started the engine died.
It lost compression in the first chamber with only 80,000 odometer miles on
it! So I just wanted to let my fellow RX-7 owners know that if your engine
starts to shudder and stutter get the compression checked out. I was unaware of
this compression problem that plagues RX-7s.
The dealer told me that the rebuilt engine is good for another 100,000 miles.
Needless to say, I did not get that much out of the other one. However, I have
owned two other '82 RX-7s and I got over 120.000 miles each on those engines.
How often should you change your vehicles transmission fluid? While most
manufacturers recommend changing the fluid every 30,000 miles, I have slightly
different thoughts. For starters, the key to a long and healthy transmission
life consists of one thing - clean fluid. Once a transmission fluid becomes dark
brown or black, its days are numbered. Transmission fluid should ideally be a
transparent pinkish red. When it becomes too dark, this is a sign that the
clutch plates are wearing away and blending in with the transmission fluid.
Think of a piece of sandpaper. If you rub a piece of sandpaper against
something, the grain wears away. This is what a clutch plate in a transmission
is similar to. Once that grain wears away, not only will the transmission fluid
discolor, but the transmission will eventually begin to slip.
The key to keeping the transmission healthy is to keep that fluid clear! My
personal recommendation for accomplishing this is to change the transmission
fluid every 20,000 miles up to 60,000 miles, then change it every year. This
will insure that the fluid remains clear and will most importantly extend the
life of the clutch plates. A transmission service every year is about $60.00. A
new transmission will cost about $3,500 installed.
One other point of interest. The majority of late model vehicles use a screen
as a filter. This screen can usually be cleaned out and reinstalled. Most
vehicles also have a drain plug which allows the fluid to be drained without
removing the entire transmission pan.
If you are having a problem with rough idle do the following:
Q: What is a throttle body, and why do I need one? I
took my 1993 626 for its annual state emissions inspection, but the garage
couldn't perform the diagnostics because the car was idling too fast. I then
took my car to the dealer and had them check out the idle.