1988RedT2 MegaDork
8/27/22 9:45 a.m.

As some of you may remember, my son and I rebuilt the 13BT in the Turbo II last year.  We've probably put 500-600 miles on it since then, and one thing is obvious.  The engine leaks coolant.

Cold starts are easy and smoke-free and the engine runs very well, but from the time it starts, until the time it is switched off, it drips coolant from the rear of the engine.  It would seem to be getting progressively worse, as it now takes maybe 8 to 12 ounces to top off the system after a 15-minute drive.

My hunch is that in failing to lube the tension bolt seals we may have torn one or more of them on final torqueing.  Is there another likely avenue? 

Thanks in advance!

Slippery GRM+ Memberand PowerDork
8/27/22 10:06 a.m.

Can you pressurize the cooling system and find the leak that way? You can buy a cooling system tester at Harbor Freight for cheap.

kb58 SuperDork
8/27/22 10:27 a.m.

I've watched my brother rebuild his a few times, for what that's worth...

The only way you might get lucky is if it's a leaking hose and the coolant is running down the outside of the engine, dripping off in that location. If it's clearly coming from inside the engine, it's sort of a done deal... it has to come out.

Javelin GRM+ Memberand MegaDork
8/27/22 11:19 a.m.

I second a pressure test. 

j_tso HalfDork
8/27/22 11:19 a.m.

Is the leak coming from between the engine and transmission bellhousing?

I wouldn't think a tension bolt seal, they're only torqued to 27 lb-ft, unless someone was really rough putting them on the bolts.

Around that area my first thought would be a freeze plug.

But first make sure it's not any of the hoses. There are 2 on each side of the rear iron, plus the temperature sensor.

1988RedT2 MegaDork
8/27/22 11:52 a.m.
j_tso said:

Is the leak coming from between the engine and transmission bellhousing?

I believe so.  I will pull the flywheel cover the next time I start it.  Last night before I shut it off I saw coolant dripping (mostly) from the bottom right corner of the rear iron, but it's hard to be sure of where it originates.  It will likely be a while before I can devote the time to working on it.  Other vehicles in the fleet are demanding service and repairs and are relied upon for transportation, whereas the RX-7 is not.

RacerBoy75 New Reader
8/27/22 2:20 p.m.

I've rebuilt many rotaries, but it's been a long time ago. My hunch is what the OP said about the tension bolt seals or o-rings. Of course I would check everything external before yanking out the engine again. 



Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
8/27/22 8:42 p.m.

Is it leaking from between the engine and trans, or is it leaking from the back of the engine?


There are four core plugs behind the flywheel, and of course the tension bolts.  I have heard of tension bolts backing out or breaking on turbo engines, but never experienced it personally.  Possibly because I have never had a turbo rotary.


I'd be more inclined to believe that it is a failed hose from the rear end housing to throttle body, since the core plugs leaking is almost unheard of and tension bolt breakage, while possible, is extremely rare.  The bolts should not leak just-because because they are torqued to more than an oil drain plug gets torqued to.  (I usually reuse the tension bolt washers because they are so expensive...)

j_tso HalfDork
8/28/22 1:31 p.m.

In reply to Pete. (l33t FS) :

I had a leaking core plug on my first rebuild. It was on the front iron by the AC mounting bracket where it's totally visible but inaccessible because of the front cover. I fingered(hee hee) some JB Weld on it and that seemed to solve it.

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