The simple differences (a little long)
 

I just picked up a 86 GXL. It was listed for $3500 but I paid $1400 because the mechanics at the used car dealer didn't know rotary engines and couldn't figure out the coolant system problems. Here is what the problem was. (these pics are not of my car, they are off the forum, so if you see your engine, that's why.) Notice in this first picture, the radiator has the normal pressure cap with the tube for the overflow bottle attached. http://home.satx.rr.com/rx7pics/engine.JPG

Now the next picture will show the pressure cap as it comes stock on S4 engines; on the thermostat housing. There is no cap on the radiator itself. The overflow tube is supposed to connect to the plastic peice under the pressure cap. http://home.satx.rr.com/rx7pics/DSCF0006.jpg

On the car I just picked up, the plastic peice was their, but it didn't have the nipple for overflow tube, nor was there a place for a cap on the radiator. This means that for some reason or another, somebody replaced the plastic piece with one that wasn't cast with a hole or with a tube spout. Some cars that came with radiators with caps, also had caps on the thermostat housing. On these cars, the housing didn't have a place for the tube cause it was on the radiator. (You can't see the radiator in this one, but you can see that the pressure cap doesn't have a tube going to it.)http://members.shaw.ca/turborex/fc/engine2.jpg

My car had no over flow hooked up, so when it got up to temp, the coolant system was pressured with no place to vent. The coolant was forcing its way out of the upper hose and spraying all over the engine. It may have been forcing its way past the water seals cause when they started the car, it would smoke. Since fixed the problem and put stop leak in the coolant, it doesn't smoke or flood with coolant or anything, and it starts right up. I will do a rebuild since I don't know the history of this motor, but at one point or another, the over pressuring might have damaged or weakend a water seal. I haven't found a plastic piece to replace the one on my car yet but what I did was drill a hole in the plastic, and used high temp RTV to seal the outer shaft from a bic pen to the plastic piece where a spout should be. I boiled the shaft in water for 30 minutes to make sure it wouldn't melt. After half an hour, it wasn't soft, distorted or discolored. Its a ghetto fix, but it works. If anyone has a piece like I need, could you hook a brotha up? Thanks, and sorry this was so long, but I thought it was something worth mentioning.

Not sure exactly what you are saying, but it depends on year, not series; on wither there is a second cap on the rad or not.

For example the top picture and bottom pictures are for an 88, while the middle one is for an 87.

The rads also switch per year. The set-up on an 86 is also different, as the overflow tank is next to the coils.

I was told it was a S4/S5 thing. But anyway, my car had no overflow hooked up and nowhere to hook one up.

sounds like the wrong year rad with the wrong year car

sounds like a confusing problem to me :confused:

....Sounds like a simple problem, and he's already found a solution....

That's pretty sad that the mechanics couldn't figure this out.....

well, if you think about it, it's kinda sad that mechanics that work at Mazda dealerships don't know how to fix a rotary, and yet I've heard multiple times of that :D