Rx7 Buyer's Guide


I've had several million people (well, maybe not quite that many) e-mail me about buying a Mazda Rx7. The question usually goes: I'm thinking of buying a Rx7, can you tell me what to watch out for. Well, if you have that question then you're in luck... as I've deciced to post my accumulation of knowledge on my web page.

Terminology: 1st Gen refers to a Rx7 built between 1979-1985, 2nd Gen refers to a Rx7 built between 1986-1991.

Pictures: You can click any of the images below to see the full size picture.

So, you are going to look at an Rx7. I must let you know that you have excellent taste in automobiles and therefore must be a superior being. Congrats. Anyway, lets talk about mileage first:

MILEAGE

High mileage on a rotary engine is not necessairly a bad thing. I know of many, many rotary engines that went past 200,000 miles before they failed. There is one main key to rotary engine longevity: MAINTENANCE, specifically OIL CHANGES. If the oil in a rotary engine is changed every 3,000 miles or so, it will almost definitly last a long time... probably past the 200,000 mile marker. Inquire about the specific car's maintenance schedule. If the owner can provide maintenance paperwork, it is a definite plus for the car. While we are on the subject of maintenance, let me tell you about overheating a rotary engine. Overheating a rotary engine is very, very bad. It will cause tubular dowel leaks (I'll explain this later) if the engine is overheated slightly, and if the engine is driven very far while overheated it will kill the engine completely. So, if you are ever driving a Rx7 and the heat guage gets much above half way, stop and figure out what's wrong.

COOLANT RESERVIOR

Before you drive the car, pop the hood. Take a look in the coolant reservior (pictured below). You shouldn't see any oil or oily residue in the reservior. If you do, it means the car has an internal engine leak. Don't mistake the normal crud/mold that is usually in the coolant for oil. Oil in the coolant will form a sludge that floats on the top of the coolant. I've also seen the sludge accumulate in the bottom of the reservior... I guess it depends on the type/amount on antifreeze used.


1st Gen and 2nd Gen Coolant Reservior (respectively)


DRIVE IT

Ok, you'll want to drive the car. Start it... it should start within the first 4 or 5 seconds. Let the car idle for a minute or two while you are checking the gauges. The alternator gauge should show around 14 volts. The oil pressure gauge should be somewhere between 30-60 pounds. After the car has warmed up, you should have about 30lbs of oil pressure at idle and about 60lbs at 3,000 rpm. Don't worry if the oil pressure isn't exactly what I said, the gauges aren't extrememly precise. As long as you have at least 15lbs of oil pressure at idle and 50-60 at 3,000 rpm, you will be fine. Now, take the car for a drive, take it easy until the engine temperature comes up. The temperature gauge shouldn't go above half-way. If it does I would be wary of the car. While I'm talking about temperature, I would suggest that you never drive an Rx7 hard when it is cold. The engine is made up of alternating slabs of aluminum and iron, which have differenent expansion rates. If you drive it hard before the temp gets up to norm, you will cause accelerated engine wear. So, the engine is warm now... it should wind all the way up to red-line smootly. If it hesitates, misses, or sputters on the way to red-line, it may only need some service (spark plugs, plug-wires, etc.), but it could be an indication of a fuel or electrical problem. Rx7 transmissions are a little 'notchy' by nature, but the transmission should shift smootly with no grinding. Also, you shouldn't be able to hear any grinding, grating, or general bearing noise out of the transmission. You may hear a slight whine when you're in the upper RPM range, but that's normal (as long as its not too loud). Drive the car around some and see how you like it. Does the suspension feel firm, is there any play in the steering wheel (there shouldn't be). Finally, take it back to where you came from and shut it off. Wait about 5 minutes and start it again. It should start as easily as before... if it is very hard to start, or won't start at all, it is an indication of low engine compression (a very bad thing).

Ooops, I should have mentioned this earlier. It is normal for the engine to rev up to about 2,000 rpm and stay there when it is started cold. The idle will slowly drop down to about 800 rpm as the engine warms up. Now, this is important.... if you start and Rx7 cold and then immediately shut it off (while it is still idled up), it will flood. A flooded rotary engine is very hard to start if you don't know the trick to it. See the 'Repair' section of my page for details on the easy way to un-flood a rotary. If you don't want it to flood, just wait until it idles down to normal before shutting it off. I'll explain why they flood under those circumstances some other time. BTW, the cold-start-quick-shut-down procedure is the only thing that I know of that will flood the rotary... just don't do it and you won't have a problem.

SMOKE

Ok, it is normal for a rotary to puff a little white smoke when the engine is started cold. However, it should not be smoking at all after the engine has been running for 5 or 6 minutes. You will notice this smoke smells extremely gassy. This is because the rotary runs quite rich for the first minute or two after being cold started (hint: this has something to do with the flooding problem I mentioned above). You should see no smoke in the rear-view mirror while driving the car (unless it's really cold outside or something). If you see alot of smoke, or it smokes heavily under accleration, then stay away from the car, it has probably been overheated or abused at some point and is burning oil or coolant). Also, check the rear-view for smoke while running the car to red-line... you shouldn't see any. Also, red-lining a rotary will not hurt it at all (but I wound't do it while the engine was cold) unless the engine has some kind of major problem. A healthy rotary enjoys red-line (really).

LEAKS TO LOOK FOR

After driving the car, pop the hood and take a look for oil and coolant leaks. Coolant leaks are fairly rare, but easy to fix if spotted, so I won't go into them. Now for the oil leaks: there are several common types that rotarys develop. The most common leaks come with age and are easy and inexpensive to fix, so I'll talk about them first. You will usually see a lot of oil beneath the oil filter on the driver's side of the engine. It is there because most people manage to make a mess when chaning the oil. However, it is common on older engines (past 100,000 miles) for the two o-rings beneath the oil filter pedestal to fail, causing a lovely leak. Fortunately this is an easy leak to fix. You need two $2 o-rings, a 10mm wrench, and about 10 minutes to take care of this leak (see the 'Repair' section for the details). The oil pressure unit just below the filter can also leak (but it's rare), but it is also a fairly inexpensive fix (about $40 for a new one). Below is a picture that may help you visualize what I've been talking about:



Now take a look underneath the front of the car. Do you see any evidence of leaks? It is common for the oil cooler to leak in the 1st Gen cars. The oil coolers in the 2nd Gen cars do leak ocassionally, but not as often as the 1st Gen cars. To diagnose an oil cooler leak, just look under the car. The oil cooler looks like a small radiator that sits just below the real raditator. Look on the driver's side of the cooler where the two oil lines connect to it. If there is a buildup of oil there, or if oil is actually dripping on the ground, then you've found a leak. Take a look at the pictures below for clarification. You can get a really good look at the oil cooler on my race car (below), because I haven't gotten around to installing the front valence (which usually covers it up). The area where the oil lines connect is circled, but they connect from the back-side (kinda hard to take a picture of).



Here's what's nice about the oil cooler leak. It is a good bargaining point. It costs around $350 to buy a new oil cooler. So you can point that out and hopefully get the owner to lower his price. However, upon getting home, you can remove the oil cooler and take it to a radiator shop and they should be able to fix it for around $30. Now, don't come crying to me if you can't have your cooler fixed for $30. You may actually have to buy a new one, but in every single case I've encountered, the old cooler could be repaired inexpensively. See the 'Repair' page for the details.

You may see some oil around the oil pan, but I wouldn't worry about it unless there are major amounts of it, or it is dripping onto the ground in decent amounts.

Now we come to the 'bad leaks' section. Rotarys will sometimes develop leaks between the aluminum and iron housings on the driver's side of the engine. These leaks are usually caused by 1) overheating of the engine or 2) use of synthetic oil (it causes the internal seals to shrink) or general poor maintenance. Said leaks are called 'dowell pin leaks' because they generally start where an interal dowell pin is located. The dowell leak has pros and cons. On the bad side, you have to rebuild the engine to correct the problem, which is pretty expensive. On the good side, the dowell leak will not usually affect the performance of the engine (unless you let it run out of oil), it will just use a little more oil than usual and make a messy engine compartment. Take a look at the engine below. It had a good dowell leak going on in the upper left corner, and one trying to start in the lower right corner (no oil came out there yet, but you can seal the internal sealing agent being forced out). The picture on the far right shows another common area for the oil from dowell leak to gather. This particular engine didn't have the problem there, but if it did, you would see oil gathering in the dip just to the left of the MAZDA emblem.



ELECTRICAL PROBLEMS

The 1st Generation Rx7s had very few, if any, electrical problems. However, the 2nd Gen cars, especially from '86-'88 were plauged with a few common electrical ailments. Namely the Logicon (heater/AC controls), clock (clock/warning light cluster), CPU (horn, brake lights, etc.), and the CLUSTER SWITCHES (windshield wipers mostly). Now, before you freak out, let me tell you that almost all of the above problems can generally be repaired for nearly nothing. All that is required is to remove the bothersome component and resolder it. The only exception is the wiper switch, which can sometimes be resoldered, but sometimes has to be replaced (about $250). If you are at all handy with a soldering iron, you can view my 'Repair' page for details on fixing these problems almost for free (I guess solder costs somthing). Basically, Mazda used a sub-standard soldering process on their circuit boards, so vibration sometimes causes the solder joints to break... causing them to need resoldering. At any rate, check out all of the electrical controls. Does the header/AC fan work? Does the defrost work? Do all the little buttons on the heater control panel do what they're suppose to? Does the windshield wiper intermittent setting work? Does the horn work? Does the clock work all of the time? Just try everything out. If you find something wrong, you can use it as a bargaining chip. Plus you'll know that you can usually (but not always) repair the problem with a good old RS soldering iron.

OTHER NOTES

Lets see, what have I forgotten? A rotary engine will use between 1/2-1 quart of oil every 3000 miles, depending on how hard you drive it. This is normal, its suppose to do that. It uses oil to lubricate the apex seals and the used oil gets burned up in the combustion process. On this note, you might want to stay away from Synthetic Oils in a rotary engine. For one thing, they don't burn as well as mineral oils, hence they leave a residue in your engine (because the rotary engine purposefully burns oil as parts of its lubrication process). Secondly, some of us believe that synthetics cause certain o-rings and seals to shrink, there-by causing leaks.

If you are looking at a Turbo-Charged 2nd Gen car (Turbo II), all of the above stuff applies. You should also look for cracks around the exhaust manifold where the turbo charger bolts on (passenger side of engine). The boost gauge should come up smoothly and completely and there should be no lurching or dropoff of power at you approach the higher rpms. Also, there should be no strange sucking or whistling sounds when the boost is up.

Finally, I have only written about the Rx7 specific stuff that you should look for on a used car. All the 'normal' used car look-fors apply (tires, shocks, brakes, etc.).

Ahh, my fingers are tired... especially after drawing all those nice pictures for you guys to look at ;)

I hope this helps out. If you have any questions, e-mail me at disney@utkux.utcc.utk.edu


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