I'm wondering still after my coolant seals blew what can cause the thinning of metal in housings in a rotary engine, specifically a s4 engine.

I had an engine rebuilt that had a hole in it in a housing where the coolant passage was and 25k miles later it blew again.

I'm wondering if wear/age and/or being previously overheated can contribute to it breaking again for the same reasons, is this something that happens in all rotary engines. (Basically having been overheated made the engine warped /thinned out; potentially cracking the metal, etc)

I overheated the engine initially after installing it a few times because I was unaware that my clutch fan was bad; it wasn't extremely overheated just up to about half on the temp gauge. After the car was shutoff the overflow would gurgle and make a lot of noise and steam would come out if I took the cap off.

The engine was going low on coolant over time, buzzer going off, I always kept an eye on it filling it regularly.

In the winter it was impounded, when I got the car back I started it up and it was sputtering blowing white smoke out like a banshee.

The impound obviously didn't get a key, but I'll never know if they did start it and mess it up on me. I ended up selling the car after because I couldn't remove the engine where I lived.

I'm looking to get another rx7 in the future

rotary > pistons

 

Overheating will warp the housings, neglecting coolant maintenance causes rapid erosion/thinning of the seal lands.

 

The thinning and pitting of the cast housings is called cavatational erosion caused by tiny air bubbles that are formed on the housings especially in rusty areas from vibration in the little engines , where the tiny bubbles actually implode against the cast housings causing a tiny microscopic piece of iron to come loose from the cast ( that is what forms the black **** in the cooling passages , the brown is obviously rust and it also contributes to the problem ) I think that is also why all the air bubbles in the cooling system even when things are working well .

If you have it analyzed you would find that it is mostly iron . most coolants have additives to help prevent this action but you can also buy additives for the cooling system that pretty much stop it ,.. Using good clean demineralized water if that's a word also helps . In the past this problem was very common in diesel engines on the cylinder sleeves , some of them were so bad they actually made holes in the sleeves and allowed coolant to leak into the cylinder .. There are those that think I am crazy but that doesn't mean I'm wrong .. have a good one . Gerald m.

 

I once rebuilt a customer's engine and saw the sealing surface on the front iron near the intake dowel had a corrosion damage. It was so bad the sealing surface lost a good chunk of iron and the engine was burning coolant. Poor coolant maintenance can cause corrosion and let water leak into engine. Other one is overheated housing starts to warp during operation and expose the water seal directly to detonation, which cause the seal to break. The same engine that had water corrosion also had the detonated water seal.

 

So the other housings that was reused could have basically done the same thing.

rotary > pistons

 

Yes...careful inspection of the parts going into a rebuild can avoid both problems.

 

Why? simply put, Mazda was DUMB.

they moved it back in later series. but too late.

 

I had it rebuilt by rotary resurrection, kevin landers. It ran for 6 years but only 25,000 miles before the seals really blew out. I drove it hard, redlining quite often to the end of the tach (7-8k), was streetported with full exhaust, ignition, etc. Running with open 5/6 ports.

 

I lost two motors to this problem. Save the money and buy new irons (while you still can.)

 

the walls don't thin out over time, each iron will have different wall thicknesses from the next, there is no rhyme or reason why some irons have many thin walls and some actually don't have thin walls at all. casting variances and tooling that cut the coolant seal channels always has some leighway.

electrolysis and acidic erosion attacking the walls weaken them. excessive heat(rapid expansion and contraction) eventually cracks the walls with the help of compression pushing the seals against the wall to create the fracture.

not everyone has $1500 to buy new irons with, then you also may as well replace the rotor housings as well which is another $1100, new bearings, oil pump, all new seals... looking at $4k+, not in everyone's budget.


https://www.rx7club.com/group-buy-pr...ntion-1006993/

 

Beat me to it:

https://www.rx7club.com/group-buy-pr...ntion-1006993/

 

buy rotary evolutions revolutionary rotary savers!

i hear that each one is tenderly and meticulously hand crafted with care.

 

heh, that is true. i have to weld the seams with an oxy acetylene torch and clean up the seams afterwards. the material is also cold rolled and trimmed before it even gets to me. they may not look like much but there is a bit of time into each one of those little strips of metal.

i originally tried tig, mig, arc then spot welding... the results were more lost material than finished product. stainless isn't a very easy material to weld, add in the fact that the material you are welding is about as thick as a few dollar bills stacked up and a fraction of an inch wide.