This has been bugging me for a while, and I've heard
all the traditional ideas, they just don't adequately describe what is going on. I think I've finally figured out the problem:

The phenomenon is known as electrochemical degradation, or ECD.

It occurs because the rubber O ring, liquid coolant (ethylene glycol antifreeze and water), and the engine internals/radiator fittings form a galvanic cell or "battery." This chemical reaction causes microcracks in the O ring, allowing the coolant to attack and weaken the rubber.

With the rotary's abundant aluminum and iron internal plates in close proximity to each other we literally have a more powerful "battery", hence the premature failure.

How to prevent O ring failure from happening again after you get a rebuild? (which HAS been happening in epidemic proportions) easy: eliminate the aqueous based coolant - and while I am not a fan of Evans because of it's extravagant price - (and I really don't think it works any better to cool than a well maintained glycol based OEM system) - it just could be the best investment available to keep that rebuild running forever.

That's my thesis and I'm sticking to it.

 

Racing Beat light weight aluminum side housing will get rid of most of the iron (only double the cost).

If that thesis gets you in to UCLA hook me up with some chearleaders!

 

I like informative posts.

 

ONLY?!! Sign me up!

 

Me too! Even if I can't understand them... LOL

 

Actually, Mr. Wankel (the forum member) tells me that o-rings fail because of some right-wing conspiracy to protect the interests of piston engines.

 

Hmmm interesting. However, distilled water isn't electrically conductive, would ECD still occur in that case?

 

^ distiled water? Do you think "ANY" race shop or dealer will go out of their way to buy distiled water or will they use free tap water? Even if you provide the water they may forget and still use tap and not tell you.

 

 

Evans coolant isn't aqueous-based? What is its primary composition then? (not being a smart-***, just seeking info)

 

Your coolant will absorb minerals from the coolant system which should make it conductive.

 

Nope, no water. Water would contaminate it.
Search for their website to read more about it.

 

It's not electrical conductivity that matters, its the chemical reaction. Ever note that only copper tubing is (or should be) used with piping leading directly into a water heater? That's because if steel-based pipes were used, electrolysis (which is sort of what RonKMiller is talking about) would eventually corrode those pipes into a complete mess.

 

Running 100% distilled through the winter, even when the car is stored in a garage, will kill your O-rings. Don't ask how I know this :p

Also, if you run pure distiled you will have corosion problems. On a positive note it definately lowered my temps over the 60/40 mixture I used to have.

Semi related question: Isn't there a way to use a metal rather than rubber seal?-maybe press a tube into the coolant passage section that connects the housings.

 

Excuse my manners.

GREAT THREAD

 

Glycol- (come derivative of it) is used for coolant

 

I was thinking the same thing. Like zinc or some other "soft" metal, or maybe a hard metal that was stranded and tightly braided. The braided metal might let some gas through, but we could finally put that AST to work.

 

Ron AKA Mr. Minister of Optimistic Information may have something here.

It's a known fact that one can determine when to change coolant by measuring the voltage difference between the coolant and the block. If it's more than 1.0 V, change the coolant. Don't believe me? Take a sensitive digital voltmeter, stick the positive probe into the coolant fill cap and the other probe on the block, you'll see a voltage difference.

Now as to distilled water: Yes. water is a great solvent meaning that it loves to dissolve all other stuff around it. Distilled water has almost no minerals in it so it tries to dissolve the block. That's why I run coolant mixed with tap water: plenty of minerals in it.

But hey, this same action occurs in pistons also but I don't see alot of head gasket problems in 15 years old Toyota (iron block/ aluminum head) or Mazda pistons (iron/aluminum). Hell, even NA rotaries last 150K or more.

So I think your premise is part of it: the heat cycling, the voltaic degradation, the make up of the o-ring itself. But like you said, there ain't no icoolant ring problems with rotary just like there is no Americans in Bagdad.

 

Yes. But that requires the housing and the end plates to be of the same material. The o-ring allows for thermal expansion of different materials. And the o-rings are designed to move in its groove for sealing.

When I first split open the old Subaru flat four I found that it doesn't have a head gasket b/w the block and the head as they are of the same material. B/c it's the same material, they expand at the same rate w/o requiring a gasket in between. Don't know about the new Subaru motors though.

 

Not sure I agree (I really am not sure). I think it's simpler than that - Mazda used a material that was inadequate for the job.

Viton? (Not metal, expensive, but cheaper than a rebuild)

Wrong. It's actually a left wing conspiracy resulting from poor fuel economy.

 

Most aqueous solutions (water!) are corrosive to ferrous and aluminum alloys that build weak oxide layers. Even austenitic stainless steels are suceptible to aggressive cracking and under deposit pitting at coolant system temps.

Distilled water only helps prevent gross mineral fallout/deposit as compared to tap water. If your chosen coolant has a poor add pack and reacts with blowby gases or decomposes with time/temp it will suffer from mineral deposit too.

Evans, good choice for me so far.

 

What about silcone O rings? Do they make them and do they last longer?

 

. The conversation about the alloy end plates is what made me think about press fitting

 

The silicone O-ring gaskets are supposed to last longer...at least that's what Dave Barninger told me when he reassembled my Malloy reman with better parts

 

Only problem with Evan's is that it has almost HALF the thermal conductivity of water. Ouch.

Also, it is (Propylene Glycol) 100% water soluble, so don't listen to that nonsense about getting 100% of the water out of your system