what would cause my coolant seal wall to fail? It looks like it cracked and rusted but the rest of the cooling passages look good.

 

Corrosion, overheating, etc

 

Pic?

 

Can that happen if you overheat the car just one time? I feel like I'm walking on egg shells with my motor when I hear stuff like this. Mine didn't exactly overheat but it boiled over a little.

 

I believe that the main culprit is people not flushing their coolant system often enough, this allows the iron to rust out and then cave in. Another issue besides the old coolant is the use of tap water. You should always use distilled water in the coolant system. The minerals and iron in normal tap water form deposits inside the engine, which lead to internal rust and retaining wall failure.

Retaining wall failure is not the outcome of overheating, which results in melted coolant seals this is evident when the engine is torn down. The final symptoms are similar however coolant seal failure is typical more gradual than retaining wall failure, which usually causes drastic chamber flooding all at once. We have seen coolant seals in great shape however the retaining wall failure caused it to loop into the coolant passage.

 

What is the recommended coolant flush interval to prevent this? What coolant and it's ratio of distilled water do you believe to offer the best protection? What location in the coolant system would you place a sensor to monitor temps?

 

yes, the car did over heat when one of the fans failed
I also did not change the coolant often enough and used tap water

I hope this info helps some of you out there

that is the front iron housing by the way
now im looking for a front iron housing and it seems they are not easy to find
I will be posting a wanted ad in case anyone know of one please let me know

thanks for the info guys

 

i disagree, i already posted a thread devoted to this topic only just a few days ago in the 2nd gen section(they have more failures than 3rd gens do).

i've actually only seen 2 engines with coolant seals that liquified and they got more than just hot..

 

What is it you disagree with? FD's have plenty of coolant seal failure, actually far more than the FC. They both have their fair share of retaining wall failure. I see it on both high and low mileage engines.

So time to explain your statement. Not just some blanket "I disagree"

 

I agree - good post. Pretty sure this is what killed my coolant seal recently. I flushed once per year, but used tap water.

 

Stupid question but is poland spring water in the jug the same as tap? Lol

I recently blew a hose and had to add some prestone + poland spring water I got from a nearby quickchek. I never overheated my car and I will flush the car probably this summer with peak 50/50 but you think im fine for now?

 

didn't feel like regurgitating what i said in that thread here so i'll simply give you cliff notes.

cast iron is a brittle metal when heated and cooled rapidly. the thin casting walls due to mazda's negligence of their thickness causes them to fracture when cooled too rapidly after severe heating. the front and mid irons tend to break more often than the rear because the front half of the engine can be cooled more quickly after being superheated.

yes the irons can simply fail naturally but i have seen plenty of thin walls eroded simply by neglect that held up fine where others came in after a cooling system issue overheated the motor which resulted immediately in the torn down engine having a broken seal wall. i'll say it could have been the iron fracture that caused the issue first but usually the seals are too clean for me to believe it had been like that for long.

it takes a lot of heat to "melt" the coolant seals to the point that they liquify. in the only two cases where i have actually seen the seals turn to a liquid to fail the engines had been run so hot until they failed to run any longer.

generally in third gen engines when you see just a simple coolant seal failure you can trace the exhaust gases right through the gaps between the rotor housing and iron walls to the blown spot in the seal. this points to boosting on a cold engine burning the coolant seals because the gaps have not been sealed up by allowing the engine to fully warm up before beating on it(noted by dark and low spots on the rotor housing seal surface, usually right adjacent to the leading plug at the highest pressure point in the engine when running). old worn coolant seals are much more susceptible to this failure than new seals are.

i've spent a fair amount of time trying to figure out the cause and ways to correct it.

i followed RX007's post after he overheated his engine due to a cooling system failure, not related to the engine. overheated the engine then i pointed out the fractured front iron in his pictures because i had suspected it after he said he drove the car after overheating it, which is what killed the iron prematurely. i was looking for something of the nature knowing that it probably didn't come out unscathed by a severe overheat session with just the coolant seals failing(sometimes they do but it makes the irons that much more brittle for the next round).

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/first-engine-pull-pictures-945593/

but if you want to tell yourself and give your customers the impression that it is mainly a maintenance issue, that's up to you. i'm sure you will say it is because of all the crap in the coolant channels which eroded the wall, well we both know that they always have crap in them.

 

Well I disagree. I have seen plenty of overheated engines that do not have any wall failure. Conversely I have also seen plenty of retaining wall failures on engines that have never been overheated. Many of them super low mileage, that have spent most of their lives parked, just rotting away internally, then when finally fired up the wall collapses with instantaneous flooding of the chamber.

The seals do not need to be "liquified" to loose their ability to contain the cooling system.

I doubt Polland water is distilled, it is most likley a mountain spring water full of healthy minerals.

 

i did mention that it doesn't always take severe overheating to break the walls, sometimes they just fracture and your low mileage comment contradicts the issue of water impurities being the culprit(but you are correct that they don't help and will thin out walls that may have once been acceptable, but i have let go plenty of gnarled iron walls that have yet to fail even now, close to 10 years since i built them).

cast irons should have never been cast so thin, the thinner it is the more easily it will crack when heated and rapidly cooled, add in impurities in the cast and even a perfect looking wall can crack with simple acceptably normal driving habits.

BUT more often than not if you were to blow a radiator hose for example and keep trying to gimp your car to a service station, the results wouldn't be favorable for that engine. and i dont just mean for the coolant seals.

a perfect iron can crack for several reasons and i don't think that either of us are incorrect but i would simply say that both of us are correct to a degree. the main issue is that it needs a workaround or the problem will ALWAYS exist regardless of how well a person takes care of their vehicle.

 

I don't think this was my case, but also seems to be quite common. Interesting theory.

 

Any opinions on distilled vs. de-ionized water? Same? Or is one better than the other for engines?

 

no experience with de-ionized. distilled is readily available most anywhere so no use beating yourself up to get specialty water for a simple purpose, like the evans guys who need to top off their cooling systems and have none readily available.

 

Do you think the different expansion rates of iron vs. aluminum contribute to hot gases getting past the coolant lands when the engine is cold and you get on it too early?

 

yes, of course there is some seals that can take the abuse better such as the rotary aviation/mcmaster carr coolant seals but they do have a tendency to chafe the outer skirt off(wear holes in the outer layer) after about 2-3 years of daily use which can eventually lead to premature coolant seal failure symptoms. i'm still a bit torn on what seals are best for everyday high performance use, the OEMs are great when new and elastic even for this issue but they are not reusable if you ever need to tear the engine down for one reason or another.

i also use a high temp silicone sealant when assembling the engines on the seal surface areas to help seal any intermittent expansion gaps in the engines.

 

Nah i know poland spring water is not distilled, just wondering if its bad to have put that into my car in the meantime over tap water (which i've never done).

And i didnt know how bad it was internally to boost on a cold engine. I have done that a couple of times in the past. That is now put to an end.

 

this motor I had in my car for over 30k miles in only 10yrs so I fall under the category of hardly driven and not so good coolant maintenance history. My car is basically stock except for dwn pipe and cat back.

i dont boost until its up to temperature, fyi

Can anyone comment on welding the cast iron coolant seal wall?

I have seen some pics and I know people have tried it. This is not something I am willing to gamble on, but I am curious if anyone has done this with some success.

I am curious because i have seen this repair before and now I was offered an iron housing that had been welded to repair the broken seal wall to replace my broken front iron and was assured it would be fine. I said, no thank you.

So, im still searching for a front iron hosing not ported.

 

rather than saying things twice i'll just put a link to the other thread since this is a much more common issue with 2nd gens.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/why-do-coolant-seals-fail-some-answers-you-should-know-953847/

 

This would be exactly the scenario that I previously posted. I would have to say that the majority of the engines I have seen with retaining wall failure fall into this category. The issue is that very low mileage cars have a tendency to have less maintanence done to them as they are rarely driven. For example we have cars come into the shop with 40K miles that have never had the fuel filter changed in 17 years.


I guess there is someone in this thread that can't seem to grasp the concept that mileage and age are not directly related.

10 or 15 year old coolant is still 10 or 15 years old regardless of mileage. The major problem is that the pH of the coolant changes. The pH indicates the acidity of the coolant. As coolant oxidizes, acids can form that will lower the pH. If the pH is too low, corrosion of iron will increase. If the pH is too high, corrosion of copper and aluminum will increase.

The conductivity also changes. Conductivity is the measure of the coolant's ability to conduct electricity, and is proportional the amount of dissolved solids in the coolant. As the coolant ages and more inhibitor is added to replenish lost corrosion protect, solids build-up and the coolant eventually becomes saturated. At this point solids can start to build up on the walls of the cooling system adversely impacting on the systems heat transfer capability

The solids (or previously mentioned "crap") do not get into the coolant system via some sort of magical method. They were always there as part of the engine, that is slowly disintegrating with time.

 

even flushing the cooling system professionaly seems to not get out all of the junk floating around in these complex passage engines.

so what's your fix then? i've pulled apart engines i built only a year prior and they have solids in the system again where i cleaned the engine thoroughly and drained the radiator completely. i can't say it was due to old coolant or lack of maintenance but that the solids were somewhere still in the system or really just do build back up that quickly and there is no easy way of getting it completely out or eliminating it from coming back.

 

Here is a good example of an engine with 35K original miles on a S5 Vert with retaining wall failure. Car sat in storage in FL most of it's life. Car was sold to our customer and within 2000 miles of daily driving the wall collapsed. Notice the coolant seals, bearings, housings are all in great shape. http://www.banzai-racing.com/kendall...down_03-05.htm