Causes for coolant seal wall to fail
05-16-11, 11:24 AM
#26
alright then, i do agree that the acidity of aged coolant/mineralized electrolitic coolant does not help the integrity of the irons but i do still believe that the metal is fatigued by age and heat cycling, i don't think you can also deny that cast iron is a brittle metal naturally and not allowing it to cool down slowly rather than letting the engine heat soak while the radiator cools then starting the engine which dumps all the cool water into the front half of the engine which cools it down rapidly is either the possible cause of failures?
most iron failures occur after overheating, if you don't agree with that then your customers are lying to you about cause of failure or you have been lucky enough to have only had customers who cared well for their cars who come in, or rather the reverse which would be old coolant but no other cooling system issues i mean.
yes i have also seen plenty of engines that sat, never were overheated and had ate an iron randomly which i would chalk up to your theory for failure.
most iron failures occur after overheating, if you don't agree with that then your customers are lying to you about cause of failure or you have been lucky enough to have only had customers who cared well for their cars who come in, or rather the reverse which would be old coolant but no other cooling system issues i mean.
yes i have also seen plenty of engines that sat, never were overheated and had ate an iron randomly which i would chalk up to your theory for failure.
Last edited by RotaryEvolution; 05-16-11 at 11:28 AM.
05-16-11, 12:08 PM
#27
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just some advice to you and everyone else on this thread... i got some more stronger coolant seals (frogot where from but i will find out) that will take at least 7 times for the coolant seal to blow.... although tested on a used 13b na motor from a 2nd gen it only lasted 5 times from overheating
05-16-11, 12:40 PM
#28
just some advice to you and everyone else on this thread... i got some more stronger coolant seals (frogot where from but i will find out) that will take at least 7 times for the coolant seal to blow.... although tested on a used 13b na motor from a 2nd gen it only lasted 5 times from overheating
05-16-11, 01:30 PM
#29
Racing Rotary Since 1983
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i agree w most of what has been posted above...
the rotary engine compression seal contains alot of engineering as it should since it's job is daunting and it's just a piece of rubber in a groove w a thin shield protecting it from meltdown. meanwhile it is anchored in cast iron and interfaces w aluminum... two quite dis-similar metals w re to expansion.
while coolant breakdown is always working against heat transfer generally rail failure occurs in the areas containing combustion chamber pressure/heat as evidenced by the photos in the thread.
my primary point is that if a compression seal is breached, if you start pushing coolant out, it is immediately time to rebuild the motor. if you fail a coolant pressure test, i e you are unable to hold constant pressure... time to rebuild.
once a compression seal is breached with every power stroke hot gasses are moving past the seal and directly attacking the seal rail which is only a tenth of an inch or so. in time and inevitably the rail will be eroded by heat and compression.
don't drive the car if you fail a coolant test or you will be buying a new iron.
we can learn from piston engines. visualise a four cylinder motor... (i know heresy)... let's say the cylinder head gasket is breached between one and two. one is TDC while two is BDC. so one pushes combustion thru the breach to the next cylinder which is down in the bore.... and vice versa. in short order the compression and heat will actually erode a path on the block surface between the two cylinder bores... maybe a tenth of an inch of pure erosion by an inch wide.
the same forces are at work on any slightly breached rotary compression rail.
the easiest way to blow your seals is boost the motor before you reach proper operating temps.
not helping the situation is the potential width-change in the rotor housings from being slightly overheated... as per factory spec rotor housing width must vary less than 2.4 thou from the coolest point (top) to the hottest area which not incidentally is where the pictures show the rail was blown away.
probably half the rotor housings i see on used FDs don't meet the standard.
and yes you can re-weld a rail but by the time you pay for the service you could just buy another good condition iron.
don't drive an engine w a coolant test failure.
always warm the engine before boosting
distilled water ONLY. minerals don't conduct heat.
howard
the rotary engine compression seal contains alot of engineering as it should since it's job is daunting and it's just a piece of rubber in a groove w a thin shield protecting it from meltdown. meanwhile it is anchored in cast iron and interfaces w aluminum... two quite dis-similar metals w re to expansion.
while coolant breakdown is always working against heat transfer generally rail failure occurs in the areas containing combustion chamber pressure/heat as evidenced by the photos in the thread.
my primary point is that if a compression seal is breached, if you start pushing coolant out, it is immediately time to rebuild the motor. if you fail a coolant pressure test, i e you are unable to hold constant pressure... time to rebuild.
once a compression seal is breached with every power stroke hot gasses are moving past the seal and directly attacking the seal rail which is only a tenth of an inch or so. in time and inevitably the rail will be eroded by heat and compression.
don't drive the car if you fail a coolant test or you will be buying a new iron.
we can learn from piston engines. visualise a four cylinder motor... (i know heresy)... let's say the cylinder head gasket is breached between one and two. one is TDC while two is BDC. so one pushes combustion thru the breach to the next cylinder which is down in the bore.... and vice versa. in short order the compression and heat will actually erode a path on the block surface between the two cylinder bores... maybe a tenth of an inch of pure erosion by an inch wide.
the same forces are at work on any slightly breached rotary compression rail.
the easiest way to blow your seals is boost the motor before you reach proper operating temps.
not helping the situation is the potential width-change in the rotor housings from being slightly overheated... as per factory spec rotor housing width must vary less than 2.4 thou from the coolest point (top) to the hottest area which not incidentally is where the pictures show the rail was blown away.
probably half the rotor housings i see on used FDs don't meet the standard.
and yes you can re-weld a rail but by the time you pay for the service you could just buy another good condition iron.
don't drive an engine w a coolant test failure.
always warm the engine before boosting
distilled water ONLY. minerals don't conduct heat.
howard
05-16-11, 04:57 PM
#30
most iron failures occur after overheating, if you don't agree with that then your customers are lying to you about cause of failure or you have been lucky enough to have only had customers who cared well for their cars who come in, or rather the reverse which would be old coolant but no other cooling system issues i mean.
I have had engines shipped in that got so hot that the rotor housings warped to the point of seizing the engine solid. No cracked retaining walls. Same holds true for an ITS car that I watched drive the final lap without any coolant, since the cast ear on the front housing had broken off. He pulled into the pits and poured 3 ga of fresh water into the smoking hot engine. Coolant seals were shot but not a single chip in the retaining walls when I tore the engine down the next week.
The anecdotal list off experiences goes on and on.
05-16-11, 05:01 PM
#31
true, we can agree to disagree. i did have one car come back in 9 months after a rebuild with a cracked iron that the walls were all perfectly fine on during the rebuild. definitely wasn't an issue of bad coolant that killed it, but i'm sure you'll say that it was already eroded from impurities.
we all have our opinions on it and i'll stick with mine that they are all correct to a certain extent and we both have examples of extremes that don't hold true where an engine survived the test or failed without reasonable cause.
we all have our opinions on it and i'll stick with mine that they are all correct to a certain extent and we both have examples of extremes that don't hold true where an engine survived the test or failed without reasonable cause.
Last edited by mar3; 05-27-11 at 03:59 PM. Reason: Killed quote since reply was back-to-back to post in question...
05-16-11, 11:30 PM
#32
Too me this is the MAIN cause regardless of the temp variances. There really is some inconsistent wall thicknesses in these engines. Grab a set of plates and you will see the differences. My 20b had a total of 5 broken walls on my intermittent plate and one on the thick center plate. Every broken wall had unusually thin walls in it that location. Temp changes and corrosion also do play a role but, the less material you have, the easier they break plain and simple.
05-17-11, 05:51 AM
#33
The majority however is old coolant, there are always going to be the oddball situations in any failure diagnosis.
I see very thin retaining walls that have held up to all the years driving without any erosion and thicker walled irons with chunks missing with low miles. Also, I have seen it on all the irons, it is not just localized to the front and intermediate.
Word of advice, the next time someone tells you they never overheated their engine, don't start off by telling them they are lying to you. Good chance they are not.
I see very thin retaining walls that have held up to all the years driving without any erosion and thicker walled irons with chunks missing with low miles. Also, I have seen it on all the irons, it is not just localized to the front and intermediate.
Word of advice, the next time someone tells you they never overheated their engine, don't start off by telling them they are lying to you. Good chance they are not.
Last edited by mar3; 05-27-11 at 04:02 PM. Reason: Deleted text and reply to deleted comments by K...
05-17-11, 01:02 PM
#34
perhaps i just don't want to think that all irons are affected by this. because no matter how well you think your car has been cared for the sad fact is that coolant starts to rapidly deteriorate in quality in as low as 1 year(i generally recommend changing the coolant yearly to my customers anyways but knowing that i don't do it myself i doubt they have either).
the example i used of the failure after the rebuild is one in several hundred, haven't seen it before or since as for to my knowledge every engine i have built is still on the road for the past 9 years with a few exceptions of small handful of turbo engines that blew rotors(every rotary is obviously susceptible so it is not a build issue).
next question though that i have wondered about the acidity issue, why do the outer coolant seal walls not break? the walls that generally fail do not technically have any pressure being applied to them(with the exeption of maybe 10 psi) as similar to the outer coolant seal walls which are equally as thin. the inner walls do however see more heat. if the hypothesis is because the coolant seals push on them, i'm not sure i really believe that as most of the time i have to chisel them out of the groove because they are solidly in place.
i can however believe that the seals can erode to the point that gases will start to bypass and push on the walls(up to several hundred psi) but i have seen perfectly good seals hold fine until the wall broke with no sign of blowby(9 month example). i'm sure the seals do absorb most of the pressure but may put a small amount of that onto the seal retaining wall(i say a small amount because the seals literally do not break their seal against the rotor housings or chafe themselves apart in the valley).
if the acidity issue eroding the irons is the main culprit then every engine out there has a chance to fail prematurely no matter how well it is inspected and probably even maintained beyond this point, if the irons have been reused. in all honesty it really doesn't bother me either way because i believe i have found a cure for it anyways, but with anything it takes time to do tests when longevity is concerned.
and i'm not trying to make anything personal, you simply disregard that cast iron is a fragile metal to which i simply disagree and is part of the issue regardless. i do believe it has to do with heat and the fragile glass like metal involved, which is simply my opinion that you try to disprove with every post so... yeah.
the example i used of the failure after the rebuild is one in several hundred, haven't seen it before or since as for to my knowledge every engine i have built is still on the road for the past 9 years with a few exceptions of small handful of turbo engines that blew rotors(every rotary is obviously susceptible so it is not a build issue).
next question though that i have wondered about the acidity issue, why do the outer coolant seal walls not break? the walls that generally fail do not technically have any pressure being applied to them(with the exeption of maybe 10 psi) as similar to the outer coolant seal walls which are equally as thin. the inner walls do however see more heat. if the hypothesis is because the coolant seals push on them, i'm not sure i really believe that as most of the time i have to chisel them out of the groove because they are solidly in place.
i can however believe that the seals can erode to the point that gases will start to bypass and push on the walls(up to several hundred psi) but i have seen perfectly good seals hold fine until the wall broke with no sign of blowby(9 month example). i'm sure the seals do absorb most of the pressure but may put a small amount of that onto the seal retaining wall(i say a small amount because the seals literally do not break their seal against the rotor housings or chafe themselves apart in the valley).
if the acidity issue eroding the irons is the main culprit then every engine out there has a chance to fail prematurely no matter how well it is inspected and probably even maintained beyond this point, if the irons have been reused. in all honesty it really doesn't bother me either way because i believe i have found a cure for it anyways, but with anything it takes time to do tests when longevity is concerned.
and i'm not trying to make anything personal, you simply disregard that cast iron is a fragile metal to which i simply disagree and is part of the issue regardless. i do believe it has to do with heat and the fragile glass like metal involved, which is simply my opinion that you try to disprove with every post so... yeah.
Last edited by RotaryEvolution; 05-17-11 at 01:32 PM.
05-18-11, 07:27 PM
#35
question to the engine builders here... (and others too ...)
is there any benefit (or possible benefit) to take new irons and measure the wall thickness all around, and then "weld up" (not sure on correct terminology here) those areas that are "thinner", to be as thick as the "thickest" areas of the wall? basically evening out the wall thickness by shoring up the thinnest areas.
not that Im looking to use this as a "one all" preventive measure, but as one more thing to add to the list of :
- change coolant often, max 1 year, of course only distilled water... being in CA, a 70/30 or 80/20 mix is "better" to reduce said corrosive agents.
- don't drive more than 10ft if there is a catastrophic coolant leak, i.e. hose blows off. pull off the fwy, wait for a tow truck.
- dont let the car sit for long periods, get out and drive the damn car! If the car does need to sit/storage, then drain all coolant.
- dont boost till engine up to temp.
- (maybe) weldup areas of wall that are thinner.
also, are there any tests can be done to test the pH of the coolant to see if it has deteriorated outside its "normal/safe" pH range?
is there any benefit (or possible benefit) to take new irons and measure the wall thickness all around, and then "weld up" (not sure on correct terminology here) those areas that are "thinner", to be as thick as the "thickest" areas of the wall? basically evening out the wall thickness by shoring up the thinnest areas.
not that Im looking to use this as a "one all" preventive measure, but as one more thing to add to the list of :
- change coolant often, max 1 year, of course only distilled water... being in CA, a 70/30 or 80/20 mix is "better" to reduce said corrosive agents.
- don't drive more than 10ft if there is a catastrophic coolant leak, i.e. hose blows off. pull off the fwy, wait for a tow truck.
- dont let the car sit for long periods, get out and drive the damn car! If the car does need to sit/storage, then drain all coolant.
- dont boost till engine up to temp.
- (maybe) weldup areas of wall that are thinner.
also, are there any tests can be done to test the pH of the coolant to see if it has deteriorated outside its "normal/safe" pH range?
05-18-11, 10:43 PM
#36
question to the engine builders here... (and others too ...)
is there any benefit (or possible benefit) to take new irons and measure the wall thickness all around, and then "weld up" (not sure on correct terminology here) those areas that are "thinner", to be as thick as the "thickest" areas of the wall? basically evening out the wall thickness by shoring up the thinnest areas.
is there any benefit (or possible benefit) to take new irons and measure the wall thickness all around, and then "weld up" (not sure on correct terminology here) those areas that are "thinner", to be as thick as the "thickest" areas of the wall? basically evening out the wall thickness by shoring up the thinnest areas.
Yes this can be done as a preventative measure. You don't have to have new irons for this and it could easily be done on used irons. I have one thin brittle looking wall left that is still holding up. I may go ahead and just break the wall off so I can do a repair now so it doesn't break on me later down the line. The reason I want to break it off is because I would rather NOT weld brittle already eroded metal. I would rather build up new metal from scratch.
05-19-11, 09:49 AM
#37
most rebuilders would not attempt to repair the walls because it is a risk and considered only a temporary repair as it is difficult to get any filler metal to bond with cast iron. welding onto the existing metal may weaken it so i can't really comment on adding material to the thinner walls but that may be an option. keep in mind that when you weld on a material the penetration will go all the way through the ~2mm thinner walls unless you use low heat settings, which won't really do much to cast iron for bonding.
Last edited by RotaryEvolution; 05-19-11 at 09:52 AM.
05-20-11, 05:17 AM
#38
There are coolant pH test strips available at most auto parts stores. This is the most effective way of monitoring the pH. You can pick up a container of 50 for less than $20 at Napa # FIL 4106
05-20-11, 12:10 PM
#41
I have not seen any yet, but it can still happen. All the aluminum housings are susceptible to corrosion due to incorrect pH levels.
FB housing with similar coolant seals in the rotor housings
another
FC housings with too much corrosion
FB housing with similar coolant seals in the rotor housings
another
FC housings with too much corrosion
05-20-11, 12:23 PM
#42
BDC Motorsports
I'm with you on this, Banzai. Same experience I've had. Always seems to be a corrosion thing due to lack of proper maintenance on the coolant. I've even done it myself keeping an engine running with 100% water only over the long term.
B
B
05-20-11, 03:39 PM
#43
Damn that apex seal thing is kinda ghetto. Sometimes the customers themselves will authorize cheap fixes if the shop informs about such damage to save them money. For your average 13b, replacing those plates aren't that big a deal as there all over the place. As for me, if I wasn't capable of building engines and had a shop build my motor, I would have the shop find a way to repair that damage by any means. If that shop wasn't capable of doing the repairs, then I would have them send it to a machine shop that could. As expensive as the 20b thick irons are, there's no way in hell I would replace that plate if I didn't have too.
Edit: Oh by the way, my welded walls are holding up just fine.
05-22-11, 06:41 PM
#44
eventually there will be no option but to repair parts that we have, which is why i hold onto those broken irons waiting for various techniques to be developed to repair failures.
Last edited by mar3; 05-27-11 at 04:04 PM. Reason: Killed quote since reply was back-to-back to post in question...
05-24-11, 11:31 AM
#45
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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.
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.
Anyone tried this stuff?
http://www.amsoil.com/storefront/ant.aspx
Last edited by mar3; 05-27-11 at 04:04 PM. Reason: Merged back-to-back posts...
05-24-11, 11:35 AM
#46
the block drain actually does a very good job at getting about 95%+ of the coolant out of the engine, the radiator drain actually doesn't work quite as well as the block drain does so removing the radiator from the car and flushing it out will help get alot of the crap out of the bottom of the end tanks. there's nothing wrong with flushing the system with tap water, just let it drain for a few minutes before adding your mixture.
+/- 1% tap water won't affect the system that much.
+/- 1% tap water won't affect the system that much.
Last edited by mar3; 05-27-11 at 04:06 PM. Reason: Killed quote since reply was back-to-back to post in question...
05-24-11, 11:41 AM
#47
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Right - previously I had flushed the system WITHOUT draining the block, so there was still tap water in the system.
Is there a special (stainless steel) bleed valve available that would make draining the block faster/easier?
Is there a special (stainless steel) bleed valve available that would make draining the block faster/easier?
05-24-11, 11:47 AM
#48
probably but it's still not in an easy place to reach and adds another possible failure point versus the reliable old bolt/plug.
i haven't really looked into it because it would just take forever to drain adding a petcock to that spot which would also get clogged up easily. petcocks can act as a filter keeping all the crap in the system in it that your intention was to remove.
i haven't really looked into it because it would just take forever to drain adding a petcock to that spot which would also get clogged up easily. petcocks can act as a filter keeping all the crap in the system in it that your intention was to remove.
Last edited by mar3; 05-27-11 at 04:05 PM. Reason: Killed quote since reply was back-to-back to post in question...
