(Wasn't seeing much activity in New Member Technical, so I copy-pasted this here.)
I own an '88 vert. One way or another, the coolant seals are bad and I get a big puff of white smoke on startup. Obviously I need to rebuild, but I'm not 100% certain on what I need.

First of all, I have 2 engines, and I'm not sure which to rebuild:
1. 130k miles, the original one from the car, taken out many years ago. Pretty sure this one has a bad seal, I never saw it while it was in the car, but I'm told it could barely move the car.
2. Unknown miles, from a junkyard, the one whose coolant seals went bad. It felt a bit tired but ran OK.

As for tools, I have access to all the wrenches, sockets, torque wrenches, feeler gauges, micrometers, 't' gauges, etc etc etc. you could ever want, and can borrow a Milwaukee impact gun from a friend. I know I'll need a 54mm socket for the flywheel, as well as the flywheel stopper. I'm told I'll need emery cloth, fine files, high grit sandpaper (not sure if what I already have is good enough). Am I missing anything?

And the parts. A friend on a discord server told me the Atkins overhaul kit is good if you use Mazda OEM seals, so if my rotors, housings, irons are good I'll probably get Atkins' "Overhaul kit A" (link to Atkins kit) as well as 2 rotors' worth of side, apex and corner seals from Mazda. Again, if I'm missing anything please let me know

Finally, actually doing the job. I haven't rebuilt a rotary before and I don't know anyone who has, in fact the only engine I have personally rebuilt was a single cylinder, pushrod Briggs.But I think I'd be able to do it, especially with help (I know plenty of people who know 10x what I know who'd be willing to help me) and the magic of Youtube videos.

 

About the only tools you don't have listed is a pilot bearing removal tool. PILOT BEARING TOOLS, INSTALLER & REMOVER | Mazdatrix Which is basically a slide hammer. Dial calipers are useful. A rotary was the first engine I built and that was way back in the '90's before everyone had internet. Luckily word of mouth hooked me up with some local rotary guys.

 

the nice thing about the rotary is that its really simple. your 1 cylinder briggs engine is more complex....

if it was mine i would pull apart the original engine, and see what it needs. use the junkyard engine for hard parts, if needed.

racing beat sells the engine gaskets and seals as a kit too, you should check the price. the cheap way to build is to measure everything, and then only order what you need, instead of the full kit.

manuals are here Foxed.ca - Mazda RX-7 Manuals

 

Not sure if I made this clear, the junkyard engine is what's been in the car.
From what I'm told, my grandpa got the car, barely running, from an auction for cheap, my dad found that junkyard engine and put it in drove it a little, then the car sat for 15 years in a barn. Then we dug it out last summer because I needed a car. (Older sister took the Corolla off to college.)

 

even better, crack open the engine that is out of the car and see what you're starting with

 

As mentioned above about dealing with the pilot bearing\tool, I rented and used one from autozone and it worked great FYI

A couple of things I might have gone above and beyond with:
I bought the coolant leak tester from pineapple racing, not required but I didn't want to install the engine to find out of an issue there(not sure how common of an issue that is).
I also used a pineapple racing engine stand adapter but I hear it isn't required per say, I've heard of folks using a bucket or table?
As well I added a new oil pump\chain while I was that far in.

I also used an RX8 (there are 2 so had to get the right one) metal front cover gasket instead of the paper one and didn't use an oil pan gasket, instead used hondabond HT etc.
For added measure I also bought and installed an oil pan brace.


The follow materials were used:


Mazdatrix rebuild video ( it was good not excellent just my opinion)

Haynes Manual

Local builder for some guidance

 

or a trash can! i have a 3 sided milk crate and this works great. the front housing goes face down, you build up, and then its 3 sided so when you need to lift the E shaft, you can put a jack in there (or piece of wood or whatever), and then the center iron goes right on.

the part where its easier is that getting it from the floor to the engine hoist is easy, getting from an engine stand to a hoist is always really weird

 

Bad coolant seals are the most misdiagnosed engine failure mode on these cars.
Suggest you do a coolant system pressure test to see if there are any leaks and if you get any coolant in the combustion chambers.
Also suggest you pressure test the fuel system. Leaky fuel injectors could also cause a puff of smoke at startup.

 

I'm also getting coolant overflowing out of the reserve tank, as well as bubbles and overflowing when the cap at the t-stat neck is removed, and the engine is run for a few minutes, so I'm preparing for the worst, hoping for the best.
I will borrow a pressure tester and test it if I can, but the last time I pressure tested it (in auto shop class in HS last year), it needed an adapter and I'm not sure if Autozone or anyone will have it.
(Results of that last test were that the radiator cap was faulty, and opening at 7 psi instead of 13)

As for the possible stuck injector, I hadn't thought of that. It would certainly be nice to have a simple fix.

 

I pressure tested my later confirmed blown coolant seal engine, and it dropped almost an imperceptible amount. So pay careful attention to the starting pressure, it may not drop much.

Everything else you describe sounds like a coolant seal unless you've done some coolant work recently and it's misrepresenting itself. My final straw before I gave up that it was something else was the combustion gas tester for coolant. Teardown confirmed blown inner coolant seal on the front rotor.

 

Well, I have done a lot of coolant work. What really confuses me is that, last fall, I had 0 coolant issues, or at least none that I noticed. I watched the temp gauge when driving and it was always 1/3 to 1/2 of the gauge.

Then as soon as we bring the car back out this spring (keeping it away from road salt), the coolant started overflowing, dumping out the reserve tank. Then later, the upper rad hose got a pinhole leak in it. Then I replaced the lower rad cap (and I discovered my s4 had an s5 rad). Then the clamp came loose on my lower rad hose. All while nothing else had any major problems. Coincidence, I'm guessing, but a pretty crazy one.
I didn't know at that point that it was probably my coolant seals. I didn't smell any coolant in the exhaust, and I still don't. I wrote off the smoke as worn oil control rings, it's just a tiny bit blue.

EDIT: Just before posting, I remembered that one time, when I revved it in a parking garage (me and my buddies being the teenagers we are) it blew a pretty huge smoke ring. The same whitish-blue color as it did on startup. I heard that's a symptom of oil control rings, not 100% sure though. I could probably find the video and send it, if anyone wants to see the color of the smoke.

I did end up overheating it (not super horribly, about 2/3 coolant gauge) AFTER the symptoms had already started. But they didn't get any worse.

Anyways, I'm going this weekend to start it one last time then drain the coolant. I don't want to risk getting the inside of the engine rusty.

 

that is normal, the 86-88 has a real gauge and 65c is the bottom line, 110c is the top and normal running is about 1/3rd of the way up, around 80-85c

 

Just rent a block tester and buy block test fluid from a local auto parts store. $10 in the end… open the radiator cap, pour block testing fluid up to the mark in the block tester. Block test fluid is blue. If it picks up exhaust gasses from the coolant, it turns yellow. You’ll know if your rotor housing coolant seals are bad.