Oh-oh rotary coolant smell!!

Hey guys,

So spring seems to have finally sprung here in New England. I went out to the garage this afternoon, and started cleaning up a bit. Also was going to try to do some burning in the back yard. To do so I was going to use the REPU to collect the brush around the property. I checked the oil, and coolant in the truck, and proceeded to fire it up. Shortly after firing the engine I smelled the strong odor of coolant. It isn't coming from the exhaust however, but very strong in the engine bay. Am I looking at a full engine rebuild because of a coolant leak internally, or is it possible I just have a leak somewhere that I can't see yet? I'm letting the engine cool now, and hope to get a system pressure tester on it later. Pray for me.

Mine does this every time it sits for a while. The water pump housing gasket drools onto the header flange.

Alternatively, if you have an engine with coolant passages to the intake manifold, the O-rings there love to swell up and turn into coils and the rotor housings themselves corrode there. Then you get a very small coolant leak... onto the exhaust manifold.

It never leaks enough on mine to actually hit the ground, but there's telltale greenish-white staining on the front cover and the top of the header flange.

Just went through this yesterday, drove my car for the first time in a few months.

Pressure testing shows 1 psi lost in an hour, when pumped to 13 psi. No leaks that I see so far. Just pumped up to 15 psi. See if that reveals anything. Not getting a good feeling though.

Chris

Relax. If your REPU has the original engine/intake setup, it's probably the intake O-rings, and you'll never really see them leak, you'll just see some green stain on the header.

It's extremely common and nothing to get worked up about. A pair of 19mm (20mm?) freeze plugs fixes the problem permanently.

I think I replaced those o-rings a year or so ago. I was getting coolant pooling on the top side of the manifold at the rotor housings. I see no clues of a leak. The only thing that I don't understand is that I can smell the coolant the strongest in the engine bay, but not in the exhaust.

Chris

The last time I had that issue, it was the radiator. A very slow leak at the top, it would only leak when hot and under pressure. The leak was so slow it evaporated as fast as it came out. Eventually it showed up as a green stain on the radiator.

Unless you have oil and water mixing or coolant smell in the exhaust, I doubt it's a internal engine problem. It'll be something in the engine compartment leaking.

I can fix that for you, take the drivetrain out of the car that has been abandoned in your backyard and install in the REPU. And maybe beef up the rear end a little while you are there.

Look at the rad. It could be leaking/steaming in the front and it is then sucked back as steam into the engine compartment. A cold pressure test may not show it as the level is a bit low. When hot it evaporates and or you are just getting the steam out of the cooling system and it is not really leaking any coolant.

Maybe rad, but it won't reek of coolant with the engine running the way a leaky intake gasket will.

Spray a hose at the area between the intake and exhaust, and see if the smell goes away.

I keep re-iterating this because it is the #1 coolant leak on carbureted rotaries, and every year on rx7club there will be four or five "OMG coolant smell!" posts.

Just 'cause you did 'em already doesn't mean they aren't leaking. Mazda made them out of something that isn't coolant safe, or something, and they fail constantly. Between that, rotor housing corrosion preventing new O-rings from sealing for very long, and generally not wanting to have to deal with it when swapping intake manifolds, I plug the rotor housings on every engine I build. (Except the peripheral port engine I built, the intake ports went through that area )