Rotary Tech & Maintenence articles (+wav of blown eng)

[Razkal]

just some stuff i collected browsing the net and from random mags and books i typed up.
good sites are: www.wakel.net
www.project-r.tripod.com
www.craigsrotarypage.com

Troubleshooting RX-7 Cooling Problems

It seems that every spring when the weather turns hot, the RX-7 forums and mailing lists are flooded with questions related to overheating and running hot. The aim of this document is to help you troubleshoot any cooling problems you may have, thus avoiding the complications (ie. engine rebuilds) that come with overheating.
Overview
There is nothing particularly special about the RX-7 cooling system, except the fact that there are actually two in the car.
The first system is the one we are concerned with. This is the water system. Like any other car, it contains 4 key components; the thermostat, the radiator, the water pump and the fan. All are pretty standard, and overall fairly reliable.
The second cooling system found in the car is the oil cooling system. It consists of the two oil hoses at the front of the engine, the oil cooler, and the bypass thermostat. The oil cooling system is very reliable, and rarely causes problems outside of leaks. Thus, we are not concerned with this system and will be focusing our attention on the water system.
For the purposes of this document, normal operating temperature is defined as 1/4 on the stock temp gauge for '86-'88 car, and 1/2 on the stock gauge for '89+ cars. Note that the stock '89+ gauge is truly terrible and has basically three positions: cold, normal, and "new engine". If you see the gauge start to creep up, immediately shut down the car and deal with the problem. In '89+ cars, by the time the gauge reaches the "H" position, the car has been running way too hot for way too long.
Troubleshooting
The actual troubleshooting process is pretty straightforward. As the cooling system is fairly simple, the problems are also fairly simple, with easy (if not necessarily cheap) solutions.
Before You Begin
Replace all your hoses and flush the system. Replace both the upper and lower rad hose, as well as the heater hoses located at the passenger and drivers side of the engine. The drivers side heater hose is a very common failure item due to the oil saturation that results from it being directly under the oil filter. Any cracks in these hoses will result in loss of coolant and system pressure, which will most likely result in the car running hot or overheating. Flushing the system is important as it helps clean out the system, and replace old and tired coolant. Use a 30/70 mixture of ethylene glycol and water. Never use "red" coolant (Dex-Cool) as it is very corrosive to the seals inside the rotary engine.
If flushing the system and replacing hoses has fixed your problem, congratulate yourself and sit down with a drink of your choice. Otherwise, continue reading.
Overheating In Traffic (Stop and Go, Low Speed Driving)
Overheating in traffic and low speed driving has one common cause: the fan. During stop and go, low speed "creeping" and low speed driving, there is not sufficient flow of air through the radiator. Therefore, the engine has a fan to draw air through the front of the car. This fan operates off of a viscous fan clutch. Basically, the fan clutch is mounted between the fan and the engine. As cold air flows over it, the clutch loosens up, allowing the fan to freewheel on the shaft of the engine. The fan then hardly turns. As the air flowing over the clutch heats up (as the engine transfers more heat to the radiator) the clutch tightens up, spinning the fan faster and drawing more air through the radiator. The cycle continues as long as the car is running. Over time, this fan clutch can wear out, causing the fan to freewheel whether it is hot or cold. This causes reduced airflow through the radiator, and therefore high operating temperatures during low speed driving. This theory is easy to test, because once you get on the highway the car will cool right down.
Testing the fan clutch is pretty easy. Simply start the car and allow it to warm up to normal operating temperature. Shut it off, then give the fan a good flick with your hand. If it rotates more than about 1.5 turns, then odds are the fan clutch is worn. However, I have found this test to be a very bad indicator of the true condition of the clutch. A much better test is to simply pick another one up from a local wreckers (they are cheap and available) and swap it on. If this solves your problem, then the fan clutch was obviously the culprit.
As mentioned, replacements are available at many wrecking yards. You can also purchase a new unit from Mazda, but I don't even want to think of the cost. If your fan clutch is bad, you might want to put some serious thought into just replacing the stock fan with an electric unit. It will cost less than a new fan clutch from Mazda, and offer slightly less drag on the engine resulting in better throttle response. Good fans to use are made by Flex-A-Lite and are available from Summit Racing.
Overheating During High Speed Driving
High speed driving in this document is defined as highway or freeway driving. Overheating during high speed driving has two common causes: a blocked radiator and/or a missing underbelly pan.
As radiators get older, mineral deposits and corrosion build up and clog the core. If the coolant is not regularly changed, this problem is common as old coolant looses it's corrosion resistance after a few years. Checking for a clogged radiator is fairly easy. Remove the fan and fan shroud from the engine, then start the car and pay careful attention to the temperature gauge. Without the fan, the car basically has no cooling, so you don't want to overheat it. Allow the gauge to reach normal operating temperature, then immediately shut off the engine. Using your hand, feel the radiator for cold and warm spots. A good rad will be uniformly hot, whereas a clogged rad will have cool/warm and hot spots. Be careful, because the hot spots can be very hot, and the fins on the radiator can cut your hand. This test is not completely certain, as a clogged rad may be so bad that it uniformly shows "warm", even though very little heat is being transferred to the coolant. A rad shop can help you diagnose a clogged rad, and can mostly likely repair your bad one by either rodding it out or re-coring it.
The 2nd gen rads have plastic end tanks, so don't be surprised if it cannot be fixed. Luckily, aftermarket copper core rads are available from places like Absolute Radiator. If you have the money to burn, I would suggest installing either a Fluidyne or Koyo replacement. These are all aluminum, and offer much more cooling capacity than stock.
The second part of the problem can be the plastic underbelly pan. This is a plastic shroud that goes from the front of the bumper to the front subframe. It not only protects the engine bay components from damage, but serves to duct air through the radiator and oil cooler. If this pan is missing, air will hit the radiator, and be deflected down under the car instead of being forced through the car. The result is a 20%-30% reduction in cooling capacity, and increased operating temperatures. If this pan is missing on your car (as they often can be) then it should be replaced immediately. Replacements are available from Mazda, as well as most wrecking yards.
Constantly Overheating
What could be considered constant overheating would be overheating at idle and during any sort of driving. Normally, the car is started cold and the temperature just keeps increasing until the car has overheated. There are 4 main causes of this; thermostat, blocked radiator and water pump/belts.
The most common cause of constant overheating is the thermostat. While Mazda thermostats are very reliable, like everything it will eventually wear out. The thermostat then becomes stuck or sticky. This results in less (or no) coolant flow through the radiator. With no coolant being pumped through the radiator, no engine cooling will take place. Testing a thermostat is pretty simple, though rather pointless. For the minimal cost of a new unit ($20) it makes very little sense to test an old one as it is probably way past it's due replacement anyway. Replacing the thermostat is a standard maintenance item, and should be done once a year (at the same time you flush and fill your cooling system). If replacement of the thermostat cures the overheating problem, then it was obviously the cause. Note: Do not remove the thermostat entirely. This will result in an overheating condition. Always replace the thermostat with a genuine Mazda unit. Generic replacements will be unreliable in this application.
Clogged or blocked radiators must be really bad before they will cause constant overheating, so this is not a common cause. More than likely the condition was found before it got to this point. However, cars that have been sitting for a long time with the improper coolant mixture can have their radiators completely blocked with corrosion. Use the techniques explained earlier in this document to troubleshoot a clogged radiator.
In general, the RX-7 water pump is a pretty reliable unit. It's normal failure mode is leakage, which is indicated by coolant running out of the "weep hole" behind the pulley. However, badly corroded water pumps can result from long periods of sitting, and improper coolant mixtures. The result is that the impeller is slowly eaten away, dramatically reducing the ability of the pump to move coolant through the engine. This obviously results in very little cooling. The cure is to replace the pump. This should be taken as a "last resort", as normally this pump damage occurs over a long period of time and is noticeable by ever increasing coolant temperatures (over a period of months or years).
Slipping or missing belts can have a dramatic effect on the operation of the water pump. As is common practice, the airpump is often removed. The removal of the airpump drive belt from the water pump will cause the remaining alternator belt to slip under high load. This means that the water pump is not turning as fast as it should, reducing it's effectiveness. Of course, if the alternator belt then snaps, you have a water pump that is not turning at all. Presumably, this condition will be noticed by the driver before it becomes an issue (ie. lack of power, all idiot lights on, dropping voltage). Even if you still have both belts in place, the failure of either belt can cause the other to be kicked from the pulley. Again, a failure of this type is hard to miss. Older and rotted belts will also slip. The solution is, of course, to replace your belts as should be done every year.
Overheating At High RPMs
Constant driving at high RPMs will often result in increased coolant temperatures (as expected) and if continued for a long period of time (more than a few minutes), overheating. There are two main reasons. One, the engine is being asked to produce it's maximum power. This of course results in more heat, and is completely normal. The second reason is that at constant high speeds, the water pump cavitates. This means that instead of pumping, the impeller simply "churns" the coolant within it's pump housing, not really moving very much at all. After a number of minutes, this lack of coolant flow will cause increased temperatures or overheating. The solution is to install a set of under drive pulleys if you intend to run the engine at high RPM often (ie. track use). The under drive pulleys slow down the rotation of the water pump and other accessories, making them more friendly to constant high speeds.
Constant Violent Overheating (Coolant Gushing Out Of Overflow Bottle, High Temps, Car May Spew Clouds Of Steam)
This almost certainly indicates a failure of the coolant O-rings. Combustion gasses are being forced into the cooling system, over pressurizing it and causing coolant to be ejected as the gas bubbles force their way out of the system. Normally, the car will also emit clouds of sweet-smelling steam from the exhaust. The only cure is to rebuild the engine to replace the damaged seals.
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[Razkal]

Is My Engine Blown?

The rotary engine is very reliable. With only 3 major moving parts, it is immune to the little problems that may plague piston engines. However, because the rotary relies on such few major parts, this also means that it is more likely that a failure of an internal engine part will be catastrophic. Combine this with the general lack of knowledge on the rotary possessed by the general public (with regards to operation, maintenance and modification) and you will find that the "blown engine" is more likely to happen in a rotary then a piston engine. This is simply the reality of the RX-7, and should not be taken to mean that the rotary is unreliable and prone to destruction. It just means that proper maintenance and operating procedures should be observed.
Many potential buyers look at cars with a supposedly blown engine as a way to save money, or start the buildup of a high horsepower car by installing their own fresh power plant. Others are experiencing weird symptoms that can indicate a blown engine, but are not sure. For example, stuck fuel injectors can produce the exact same symptoms as an engine that has lost compression, as can malfunctioning ignition systems. This document is to assist this person in determining whether or not the engine is blown.
But first, let's decide on what exactly "blown" means. For this document, blown means that the engine has lost compression on one or more rotors. This is normally due to apex seal failure. The seal cracks, pits or just plain gets ejected from the rotor, causing two rotor faces to lose their compression (one apex seal is responsible for sealing two rotor faces). Often, the damaged seal will travel around the housing as the engine rotates, crashing into other apex seals and damaging them as well. The result is a bad housing, and probably a damaged rotor. Small cracks can also form in the apex seal, resulting in much lower compression then normal, but no other damage to the housing or rotor. The point is that it is fairly easy to find a blown engine with a simple compression test.
The Mazda compression tester is the quickest and easiest way to determine the compression of a rotary engine. However, since these units are quite expensive, we can assume you don't have one. If you do, then obviously you wouldn't be reading this document so there's no real point in telling you how to use it. A simple tester can be made by using a standard automotive compression gauge. Remove the one way check valve, and install the tester into the leading (lower) spark plug hole in the front rotor. Make sure your battery is fully charged, remove the EGI fuse, then floor the pedal and crank the engine while an observer looks at the gauge. You are not looking for excellent numbers, just three even bounces above 70 PSI. If the rotor has lost one apex seal, you will get one strong bounce followed by two very low bounces. If all seals are damaged, then you will get three bounces that barely register on the gauge. Repeat for the other rotor.
If you don't have a compression tester, it is actually still very easy to determine the state of an engine. Remove the leading spark plug from the front rotor, make sure the battery is fully charged, and then crank the engine while listening to the air exiting the spark plug holes. It should be an even rhythm of "psssst" sounds, one per every half revolution of the eccentric shaft. Something like "psst...psst...psst...psst...psst...psst". An engine with a bad seal will be very obvious in that you will hear an irregular pattern of "psst" sounds or one "psst" for each revolution. For example, you would crank the engine and hear ".........psst...psst..................psst...psst...." or something like "psst.............psst...........psst.............psst.". To help you recognize the sound, a recording of a blown engine is below. This engine lost a seal in the front rotor, leaving only one rotor face with compression. It is in Microsoft Wave (.WAV) format and is playable on probably every machine out there.

Notice the long pauses between "psst" sounds. A good engine will have a steady beat of "psst" sounds that are strong, and well pronounced. On the off chance that you have a bad side seal, you could hear a pattern of two "psst" sounds, a pause, then two more. This will look like "psst...psst..........psst...psst.......". The engine is still blown, but all the apex seals are intact. An apex seal failure will always result in the loss of compression on two rotor faces, and thus one "psst" with a long pause before another.
What if the engine is out of the car? Well, you can't do a proper compression test, but you can at least check the general condition of the seals, and normally tell if it has low compression.
You will need to arrange the engine so that you can get access to the 19MM bolt at the front pulley. Remove the exhaust manifold, but leave the spark plugs in place. Now, using a 19MM wrench, turn the engine over three times. While you are turning it over, listen for a distinct "chug" every half turn. This is caused by the pressure differential as the rotor sweeps by the exhaust port. If a chug is missing, or sounds significantly weaker then the others, then you have a problem. As with the "psst" test, a chug will normally be missing for two rotor faces.
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[Razkal]

I Overheated My Car. What Now?

Most RX-7 owners will never have to worry about an overheated car, but if you are one of the unlucky ones, the information on this page should be useful. By now, I'm sure you know that rotary engines don't take to overheating very well. Overheating usually results in warped housings, which results in the water o-rings not seating very well. This condition causes coolant to leak into the combustion chamber. Obviously, this is a bad thing.
If the car is overheating, the first thing to do is pull over. If you were running the car hard and idling would help reduce the temperature of the engine in a natural way, let it idle until the temperature gauge reads normal temp. If the car suddenly overheated due to lack of coolant or other reasons, shut off the engine immediately and allow the car to completely cool down.
With the car cooled down, it may be driven to a convenient place and examined for damage. If the car begins to run hot again, shut it down and have it towed.
Does the car still run? That is always a good sign. What you want to do is look for possible damage. Does the car belch out huge clouds of white smoke after it is started? This could be caused by coolant leaking into the chamber and being burned off by the running engine. It is rather normal for an engine to expel a could of steam when cold started or operated in cold weather, but excessive amounts of sweet smelling smoke almost certainly indicate burning coolant.
Does the car consume coolant, with no noticeable external leaks? If you continue to add coolant to the car with no external leaks seen on the engine, it may be being burned. The coolant may be leaking into the engine internally. This is what creates the cloud of white smoke. The best way to test for this condition is to look for bubbles in the coolant. With the car completely cold, remove the coolant filler cap. Now start the engine and look at the coolant through the filling hole. Do you see a steady stream of bubbles coming from somewhere in the engine? Now, rev the engine by grabbing the throttle lever at the front of the engine. Does the coolant bubble up and/or gush out? If these two conditions are present, it is a pretty good sign that the coolant O-rings are leaking and allowing coolant to enter the engine, and combustion gas to enter the coolant.
If you have performed the above test and suspect engine damage, it is best to have the cooling system pressure tested to be absolutely sure. Any damaged pressurized system will leak coolant into the engine, resulting in hard starting and cloud of white smoke. Most rad shops can provide this service.
Now, if the car shows no loss of coolant and still runs properly after being overheated, consider yourself lucky. Now would be a good time to figure out what caused the initial overheating and correct it so the situation does not re occur.
If you have suffered engine damage, the only cure is a full rebuild. The car may still be driveable, but the condition will continue to get worse until the car no longer runs. This may take days, weeks, months or even years. There are various temporary fixes that can be employed, but they are just delaying the inevitable. Better start saving for that new engine.
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[Razkal]

The "ATF Trick": The Real Truth

If you have been involved in the RX-7 community, you have probably heard mention of the "ATF trick", or "ATF treatment". It is often prescribed for serious flooding situations, and sometimes as a general maintenance item. Especially on a certain forum. However, misunderstandings about the use of automatic transmission fluid, or ATF, in rotary engines has caused damage to quite a number of cars. I am hoping that this page will provide a little info on the "ATF trick" that is rarely heard.
Basically, the ATF trick consists of introducing automatic transmission fluid into the working (combustion) chamber of a rotary engine. This is usually done by removing the leading spark plugs, and using a funnel and tube to pour a few ounces of fluid into the engine. The engine is then either rotated by hand or cranked over with the starter to distribute the fluid inside the engine. Common practice is to then leave the car overnight to allow the fluid to "do it's magic". The idea is that ATF dissolves any carbon deposits and cleans out the internal mechanism of the engine. ATF is also used in a situation of severe flooding. It is again poured into the engine through the spark plug holes. The ATF absorbs the extra fuel, and allows the apex seals form a better better seal and build up compression. The engine then starts and burns off the ATF.
The problem is, quite a number of people use the ATF trick as a general cure-all. What they don't realize is that ATF is in fact bad for the engine. ATF is a fairly corrosive liquid, designed for the environment in an automatic transmission. The seals and materials in an automatic transmission are different than those in the working chamber of your engine. While ATF may not be corrosive to the bands, clutches and gaskets in an automatic transmission, it is corrosive to carbon (which is good, and why it cleans the engine) and has been shown to affect the rubber O-rings used to seal the rotor housings together, as well as the o-rings used on the oil seals. ATF attacks all those seals, and if they were marginal to begin with, they will most certainly be ruined by the ATF trick. This is why there are so many complaints that sound like "I did the ATF trick a week ago and now my car smokes and burns oil". The ATF has damaged the seals, allowing oil to leak into the working chamber and be burned off. This is bad, and can only be cured by replacement of the seals, which of course requires disassembly of the engine. Since the ATF trick is most often used on marginal engines to try to increase the performance, problems are fairly common. So using ATF as a general "cure all" or engine cleanout method is not a good thing.
Another use is to try and free an engine that has become "carbon locked". Carbon locking occurs when a chunk of carbon dislodges from the rotor housing and jams the apex of the rotor against the housing. This prevents the engine from turning. ATF is poured into the engine in an attempt to dissolve the carbon. This procedure is entirely acceptable, as a carbon locked engine is usually on it's last legs anyway, and there's not a lot that can be done to make it run any worse. Because of the damage caused by carbon locking, the engine usually blows shortly after the carbon has been cleared.
Excessive use of ATF also has other side effects. For one, the spark plugs are fouled much more quickly. This is due to the deposits that build up as the ATF burns. It may not be a big deal, but fouled spark plugs need to be replaced otherwise they will cause loss of power and gas mileage. The same deposits that clog spark plugs are also blown into your exhaust. If you are running catalytic converters, the soot and forign matter may begin to clog up the honeycomb inside. If the converters were already marginal to begin with, the ATF treatment may be the "last straw". Of course, the engine oil should always be changed after using ATF since it will be contaminated. A slightly more amusing side effect are the intense clouds of strange-smelling white smoke. Be aware that the ATF trick will produce enough smoke to fill a neighbourhood quite effectively. This has resulted in concerned neighbours calling the fire department, police, etc.
The original use for ATF was to clear flooding. It is entirely acceptable in a situation of severe flooding to use ATF to restore engine compression and allow the engine to be started. ATF does not usually sit in a flooded engine long enough to cause damage to the seals, as shortly after the ATF is poured into the engine it is burned off on startup. However, oil works just as well and is much more benign.
There you have it, when you can and when you cannot use ATF. I hope that this saves at least a few cars out there.
Note: I have received alot of flack for this page. Many people were confused by my previous use of the term "side seals". What I really meant was "oil seals" or "oil o-rings". My mind always reverses them whenever I talk about the engine internals. This serves to confuse alot of people, and make me look like an idiot. I have corrected the terms above to make things more accurate. Obviously, ATF cannot attack the side seals in the engine because they are metal. The "ATF debate" is also not new. It has been going as long as there have been rotary engines, and won't stop anytime soon. Some have said ATF is the best thing since sliced bread, others have had their engine seriously damaged. This page is based on my experiences with ATF, and the fact that I personally know owners who have ruined their engines with this "fix all". For what it's worth.
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[Razkal]

http://www.aaroncake.net/rx-7/blown.wav
^blown engine recording...just so u can confirm..
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[NarendZORCE]

Alternatively you can use this link:

www.zorce.com/tech/blown.wav
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