Why o-rings fail. My theory.
02-22-07, 12:31 AM
#1
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Why o-rings fail. My theory.
I've got a theory on why coolant seals go early sometimes on RX7s and would love to hear your feedback.
I think that electrolysis may be the root cause. Most of know that letting these cars sit with the same coolant for too long is bad. The engines are constructed of unlike metals sandwiched together. This is the way batteries work and why these engines are especially vulnerable. to electrolysis problems. I believe that in a very short time the coolant can get so acidic that it can eat away at the seals. When I first bought my FD it came with very low miles for the age of the car and I can only conclude that it sat in someone's garage for a considerable amount of time. The unwary owner probably had no idea that he should change the coolant often (or switch to electrolysis free Evans NPG). Shortly after purchasing my FD developed a coolant leak in a metal pipe and the cause was attributed to acidic coolant. It doesn't take a big leap to figure out that the same acidic coolant that caused the pipe leak could also have damaged my coolant seal. The coolant seal problem surfaced last summer when I had coolant loss problems and finally had it tested. It's the kind of problem that can hide for awhile until reaching a certain point where it causes something that is noticed (like coolant loss). I've heard other theories on why these o-rings fail early sometimes such as sitting and drying the seals out and overheating etc. But I think that the acidic coolant may be the main cause given the propensity for electrolysis and the tendency of humans to procrastinate maintenance. I apologize if this has been written about before. I thought of trying a seach but if you type in anything about o-rings in the search function you are likely to get a list of posts longer than my wife's list of things for me to do on our house.
I think that electrolysis may be the root cause. Most of know that letting these cars sit with the same coolant for too long is bad. The engines are constructed of unlike metals sandwiched together. This is the way batteries work and why these engines are especially vulnerable. to electrolysis problems. I believe that in a very short time the coolant can get so acidic that it can eat away at the seals. When I first bought my FD it came with very low miles for the age of the car and I can only conclude that it sat in someone's garage for a considerable amount of time. The unwary owner probably had no idea that he should change the coolant often (or switch to electrolysis free Evans NPG). Shortly after purchasing my FD developed a coolant leak in a metal pipe and the cause was attributed to acidic coolant. It doesn't take a big leap to figure out that the same acidic coolant that caused the pipe leak could also have damaged my coolant seal. The coolant seal problem surfaced last summer when I had coolant loss problems and finally had it tested. It's the kind of problem that can hide for awhile until reaching a certain point where it causes something that is noticed (like coolant loss). I've heard other theories on why these o-rings fail early sometimes such as sitting and drying the seals out and overheating etc. But I think that the acidic coolant may be the main cause given the propensity for electrolysis and the tendency of humans to procrastinate maintenance. I apologize if this has been written about before. I thought of trying a seach but if you type in anything about o-rings in the search function you are likely to get a list of posts longer than my wife's list of things for me to do on our house.
02-22-07, 01:07 AM
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I think your right about it being a reason as to why those seals break. Also though i think that you were on to something before you came to the conclusion of electrolysis. What i mean is. So you got this car that had been sitting for a long time. Then it got driven and a coolant leak was exposed. Fortunately you like your car. You fixed your problem. There are a lot of people who bought these cars initially that didnt know squat about cars and probably wouldnt have even fixed something like that. That is when it would have overheated. My car had rust water for coolant when i got it. I replaced all of the coolant hoses and flushed the coolant and got 6 months out of my motor before it died. Really frustrating if you ask me. Anyway. Good thinking and all the more reason to go with evans. However i heard that it was flamable. What do you know about that?
02-22-07, 01:24 AM
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Thanks for the feedback!
No I haven't read anything about Evans being flammable. Personally I doubt it because one of the things about evans is that it is supposed to be safe for pets and the environment. Most flammable liquids are toxic (ie gasoline). It is made from Propelene Gycol instead of the ethylene glycol used in most coolants so maybe I'll do a google search and check it out. Also I have a bottle of the stuff in the garage so I can check the labels for warnings. You could be right. Worth checking out. I would still use it of course but I'd carry a couple of fire extinguishers in the car. Here is link I got with a quick search: http://archives.glastar.org/0005/msg00071.html
Of course the ultimate test would be to pour a little on the ground and throw a match at it. lol.
No I haven't read anything about Evans being flammable. Personally I doubt it because one of the things about evans is that it is supposed to be safe for pets and the environment. Most flammable liquids are toxic (ie gasoline). It is made from Propelene Gycol instead of the ethylene glycol used in most coolants so maybe I'll do a google search and check it out. Also I have a bottle of the stuff in the garage so I can check the labels for warnings. You could be right. Worth checking out. I would still use it of course but I'd carry a couple of fire extinguishers in the car. Here is link I got with a quick search: http://archives.glastar.org/0005/msg00071.html
Of course the ultimate test would be to pour a little on the ground and throw a match at it. lol.
Last edited by Silverstone; 02-22-07 at 01:32 AM.
02-22-07, 02:12 AM
#4
you must have read some of my posts on the subject and got the wrong impressions about electrolysis.
electrolysis can only attack metals since it is an electrical charge that builds up in the cooling system and erodes metals, electrolysis can start early on if you use tap water containing minerals so always use distilled water when changing the coolant. as well as you said stagnant coolant should be changed to help prevent electrolysis as the protective additives in the coolant break down over time and lack of use. just like rusty water in a cup, over time anything that is in the water will begin to seperate and heavier atomic level materials will sink to the bottom and begin to seperate.
what electrolysis attacks first is the aluminum since it is more conductive(in this case apparently) than the cast iron materials. first places you will see erosion in these motors is around the exhaust ports and around the spark plug lands inside the water jackets. i have had to toss a number of good rotor housings because electrolysis 'drilled' through those areas.
next area of concern is the irons which tend to crack at the coolant seal walls, generally only older irons crack as age weakens the cast iron and many many heat cycles, after the cast iron weakens to a point it only takes a single overheat(generally in the area of 240+ degrees farenheit) to finally push those areas to fail.
many people tend to think coolant seals in 13B engines fail on their own which is a misconception, fact is the seals themselves rarely fail but the irons that hold them in place fail.
moral of the story:
change your coolant yearly, regardless of what the coolant manufacturer recommends. run the car on a regular basis to keep the coolant flowing and prevent settling. replace the thermostat every 30k miles and check the fan operation yearly.
#1 killer of all things 13B are in this post so keep what i said in mind.
electrolysis can only attack metals since it is an electrical charge that builds up in the cooling system and erodes metals, electrolysis can start early on if you use tap water containing minerals so always use distilled water when changing the coolant. as well as you said stagnant coolant should be changed to help prevent electrolysis as the protective additives in the coolant break down over time and lack of use. just like rusty water in a cup, over time anything that is in the water will begin to seperate and heavier atomic level materials will sink to the bottom and begin to seperate.
what electrolysis attacks first is the aluminum since it is more conductive(in this case apparently) than the cast iron materials. first places you will see erosion in these motors is around the exhaust ports and around the spark plug lands inside the water jackets. i have had to toss a number of good rotor housings because electrolysis 'drilled' through those areas.
next area of concern is the irons which tend to crack at the coolant seal walls, generally only older irons crack as age weakens the cast iron and many many heat cycles, after the cast iron weakens to a point it only takes a single overheat(generally in the area of 240+ degrees farenheit) to finally push those areas to fail.
many people tend to think coolant seals in 13B engines fail on their own which is a misconception, fact is the seals themselves rarely fail but the irons that hold them in place fail.
moral of the story:
change your coolant yearly, regardless of what the coolant manufacturer recommends. run the car on a regular basis to keep the coolant flowing and prevent settling. replace the thermostat every 30k miles and check the fan operation yearly.
#1 killer of all things 13B are in this post so keep what i said in mind.
02-22-07, 03:17 AM
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Karack,
Running the car on regular basis ---> I use mine only once a week or once every two weeks for very short time (8 to 15Kms). Should i make it a point to use it more frequently? Many thanks!
Running the car on regular basis ---> I use mine only once a week or once every two weeks for very short time (8 to 15Kms). Should i make it a point to use it more frequently? Many thanks!
02-22-07, 08:56 AM
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I've been an FC guy for a LOOONG time before I got my FD, and cooling seal failures aren't near as common on the FC as the FD. Most coolant seal failures on the FC are attributed to overheating by the owner - car busts a coolant hose, guy keeps driving kind of thing.
The big problem on the FD is Mazda designed the car to run MUCH hotter. FC's typically run at thermostat opening temp - about 80 deg. C. A stock FD will EASILY get into the 100 deg. C range on a warm day - the stock thermoswitch won't kick the fans on until 107 or so, which IMHO is CRAZY hot. Also, many FD's run higher pressure radiator caps, which puts more pressure on the whole system. Just not good.
IMHO, with proper fan control and running a reasonable radiator cap (.9 bar - you can run a stock FC cap) you can keep temps WAY down. My car runs like my FC - around thermostat temps most times, anywhere between 80-90 deg. C.
I will agree coolant electrolysis is a Bad Thing - coolant should be changed once a year, regardless. I've been through FC motors that have had regular coolant changes, and the rotor housing passages were a clean aluminum color, not yellow or orange with pitting and debris build-up.
Dale
The big problem on the FD is Mazda designed the car to run MUCH hotter. FC's typically run at thermostat opening temp - about 80 deg. C. A stock FD will EASILY get into the 100 deg. C range on a warm day - the stock thermoswitch won't kick the fans on until 107 or so, which IMHO is CRAZY hot. Also, many FD's run higher pressure radiator caps, which puts more pressure on the whole system. Just not good.
IMHO, with proper fan control and running a reasonable radiator cap (.9 bar - you can run a stock FC cap) you can keep temps WAY down. My car runs like my FC - around thermostat temps most times, anywhere between 80-90 deg. C.
I will agree coolant electrolysis is a Bad Thing - coolant should be changed once a year, regardless. I've been through FC motors that have had regular coolant changes, and the rotor housing passages were a clean aluminum color, not yellow or orange with pitting and debris build-up.
Dale
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02-22-07, 12:15 PM
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Originally Posted by Karack
you must have read some of my posts on the subject and got the wrong impressions about electrolysis.
electrolysis can only attack metals since it is an electrical charge that builds up in the cooling system and erodes metals, electrolysis can start early on if you use tap water containing minerals so always use distilled water when changing the coolant. as well as you said stagnant coolant should be changed to help prevent electrolysis as the protective additives in the coolant break down over time and lack of use. just like rusty water in a cup, over time anything that is in the water will begin to seperate and heavier atomic level materials will sink to the bottom and begin to seperate.
what electrolysis attacks first is the aluminum since it is more conductive(in this case apparently) than the cast iron materials. first places you will see erosion in these motors is around the exhaust ports and around the spark plug lands inside the water jackets. i have had to toss a number of good rotor housings because electrolysis 'drilled' through those areas.
next area of concern is the irons which tend to crack at the coolant seal walls, generally only older irons crack as age weakens the cast iron and many many heat cycles, after the cast iron weakens to a point it only takes a single overheat(generally in the area of 240+ degrees farenheit) to finally push those areas to fail.
many people tend to think coolant seals in 13B engines fail on their own which is a misconception, fact is the seals themselves rarely fail but the irons that hold them in place fail.
moral of the story:
change your coolant yearly, regardless of what the coolant manufacturer recommends. run the car on a regular basis to keep the coolant flowing and prevent settling. replace the thermostat every 30k miles and check the fan operation yearly.
#1 killer of all things 13B are in this post so keep what i said in mind.
electrolysis can only attack metals since it is an electrical charge that builds up in the cooling system and erodes metals, electrolysis can start early on if you use tap water containing minerals so always use distilled water when changing the coolant. as well as you said stagnant coolant should be changed to help prevent electrolysis as the protective additives in the coolant break down over time and lack of use. just like rusty water in a cup, over time anything that is in the water will begin to seperate and heavier atomic level materials will sink to the bottom and begin to seperate.
what electrolysis attacks first is the aluminum since it is more conductive(in this case apparently) than the cast iron materials. first places you will see erosion in these motors is around the exhaust ports and around the spark plug lands inside the water jackets. i have had to toss a number of good rotor housings because electrolysis 'drilled' through those areas.
next area of concern is the irons which tend to crack at the coolant seal walls, generally only older irons crack as age weakens the cast iron and many many heat cycles, after the cast iron weakens to a point it only takes a single overheat(generally in the area of 240+ degrees farenheit) to finally push those areas to fail.
many people tend to think coolant seals in 13B engines fail on their own which is a misconception, fact is the seals themselves rarely fail but the irons that hold them in place fail.
moral of the story:
change your coolant yearly, regardless of what the coolant manufacturer recommends. run the car on a regular basis to keep the coolant flowing and prevent settling. replace the thermostat every 30k miles and check the fan operation yearly.
#1 killer of all things 13B are in this post so keep what i said in mind.
02-22-07, 10:55 PM
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Oh one more thing to keep this thread alive:
I bow to Karack who has seen the insides of many rotor housings on a regular basis. Let me just say that I think my theory was based on the assumption that electrolysis causes the coolant to reach an extremely low Ph (very acidic). I assumed the acid was attacking the polymer o-ring causing the o-ring to fail. But Karack is saying that the o-ring itself isn't what he sees failing on his rebuild jobs, so this sort of shoots my theory into oblivion.
I bow to Karack who has seen the insides of many rotor housings on a regular basis. Let me just say that I think my theory was based on the assumption that electrolysis causes the coolant to reach an extremely low Ph (very acidic). I assumed the acid was attacking the polymer o-ring causing the o-ring to fail. But Karack is saying that the o-ring itself isn't what he sees failing on his rebuild jobs, so this sort of shoots my theory into oblivion.
02-22-07, 11:06 PM
#11
My personal experience says that boosting on a cold motor is one way to hurt your coolant seals. I was running late to work on a chilly day, did a hard acceleration run on an onramp, coolant temps were 100-140F. A week or two later I had excess coolant coming out of the overflow tank.
When the motor is still cold, the housings haven't expanded and fully closed the gap yet; what you get is coolant seals exposed to a lot of combustion pressure before the motor warms up. Remember, boost adds both air and fuel, so you've got a much stronger "bang" when the spark happens.
-s-
When the motor is still cold, the housings haven't expanded and fully closed the gap yet; what you get is coolant seals exposed to a lot of combustion pressure before the motor warms up. Remember, boost adds both air and fuel, so you've got a much stronger "bang" when the spark happens.
-s-
02-23-07, 12:47 AM
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Originally Posted by sevensix
seems like it supports your theory, but instead of the seals been corroded/eaten away, its the housing surfaces around the seal that deteriorate. 
guess i'll be changing my coolant soon
guess i'll be changing my coolant soon
02-23-07, 02:24 AM
#14
i can only count on one hand how many motors that i pulled apart that actually only had a coolant seal fail, in fact it is less than that, i haven't seen a single motor of the ~50 so far that have only had a simple coolant seal failure only. well actually scratch that i had one where a customer ran the car with no water pump and it literally turned the coolant seals to liquid. that was impressive but at the same time i warrantied that motor out of generosity but i was surprised to see the engine saw temperatures in excess of 300*F and did not crack an iron.
FDs are used to higher temps normally but as i said they also have 10 years less of heat cycles on the engines so i am still seeing electrolysis killing FD motors more than iron failures. excessive temps can also be cause for the electrolysis build up in the system since excessive heat also wears out the additives in the cooling system quicker so protection is lost. whenever possible i do as Dale mentioned and lower the fan turn on points on the FDs so they do not run so hot naturally.
the other downside to the FDs and electrolysis is mazda decided to start machining around the spark plug areas inside the water jackets on the rotors housings in S6 motors, this exposes a more raw aluminum vs the cooked and sooty rough surface that is left from casting. electrolysis can setup early on in those machined areas and i have seen some very fine electrolysis set up in those areas. on one rotor housing the pinhole was so fine it was about the size of the head on a pin and went directly for the spark plug and sometimes pressure testing the engines does not turn up these pinholes and they can only be found during run in of the engine.
i have had many more nightmare builds on FDs than i have had on FCs since very rarely does electrolysis set in on FC rotor housings and i have never seen it set in on irons. when irons fail the whole casting where the coolant seal sits completely caves in because it is a weak/thin area.
my biggest beef with mazda on the 13B engines is if they would have merely made the coolant seal walls casting thicker these engines would be nearly bulletproof aside from tuning screwups.
FDs are used to higher temps normally but as i said they also have 10 years less of heat cycles on the engines so i am still seeing electrolysis killing FD motors more than iron failures. excessive temps can also be cause for the electrolysis build up in the system since excessive heat also wears out the additives in the cooling system quicker so protection is lost. whenever possible i do as Dale mentioned and lower the fan turn on points on the FDs so they do not run so hot naturally.
the other downside to the FDs and electrolysis is mazda decided to start machining around the spark plug areas inside the water jackets on the rotors housings in S6 motors, this exposes a more raw aluminum vs the cooked and sooty rough surface that is left from casting. electrolysis can setup early on in those machined areas and i have seen some very fine electrolysis set up in those areas. on one rotor housing the pinhole was so fine it was about the size of the head on a pin and went directly for the spark plug and sometimes pressure testing the engines does not turn up these pinholes and they can only be found during run in of the engine.
i have had many more nightmare builds on FDs than i have had on FCs since very rarely does electrolysis set in on FC rotor housings and i have never seen it set in on irons. when irons fail the whole casting where the coolant seal sits completely caves in because it is a weak/thin area.
my biggest beef with mazda on the 13B engines is if they would have merely made the coolant seal walls casting thicker these engines would be nearly bulletproof aside from tuning screwups.
02-23-07, 06:48 AM
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I use distilled water, with a 70water/30antifreeze mix as I do not use my car in the winter months, but still run it to keep things going...but I also add BG Supercool additive to the cooling system. Suppose to keep the PH balance normal and prevent build up of acids and electrolysis. We sell BG products at work and all of them work really well, esp the 44K fuel additive. Didnt know if anyone had any thoughts about this product. Some have said that redline water wetter eats coolant seals over time, but no real hard evidence, not sure about royal purple's purple ice coolant additive, but those are more for reducing the surface tension of the water to transfer heat better from what the product says.
02-23-07, 12:19 PM
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Those bastards.
Originally Posted by Karack
my biggest beef with mazda on the 13B engines is if they would have merely made the coolant seal walls casting thicker these engines would be nearly bulletproof aside from tuning screwups.
Those bastards.
On evans, doesn't anyone else agree that it's just better not to have to worry about all this changing and sitting etc, and use a coolant that has no water, is higher temp, and won't kill your cat? Isn't it the fact that there is not any water to conduct electric charge a better stategy than just relying on additives?
02-23-07, 02:30 PM
#18
Originally Posted by ITR
Karack,
Running the car on regular basis ---> I use mine only once a week or once every two weeks for very short time (8 to 15Kms). Should i make it a point to use it more frequently? Many thanks!
Running the car on regular basis ---> I use mine only once a week or once every two weeks for very short time (8 to 15Kms). Should i make it a point to use it more frequently? Many thanks!
once a week is fine, letting a rotary sit for longer than that they tend to start getting bitter and begin acting up, throwing intermittent fits, etc.
i don't see a problem with the Evans coolant so long as it does what it is supposed to do which is keep the engine cool. the benefits of a no pressure cooling system would be beneficial to a rotary engine.
Originally Posted by Sgtblue
I wonder if re-torquing the tension bolts would help. Say every 50 or 60k. Lot of work, but many or most usually have to drop the transmission for one thing or another about that often anyway.
mazda never made new molds when they made changes to put the coolant seals in the irons vs the rotor housings. to save a few bucks the castings are basically identical to how they were 30 years ago, with only minor changes to port size and front cover mounting.
Last edited by RotaryEvolution; 02-23-07 at 02:39 PM.
02-23-07, 02:43 PM
#19
Originally Posted by Silverstone
On evans, doesn't anyone else agree that it's just better not to have to worry about all this changing and sitting etc, and use a coolant that has no water, is higher temp, and won't kill your cat? Isn't it the fact that there is not any water to conduct electric charge a better stategy than just relying on additives?
However, Evan's just isn't as practical in the odd case of a blown hose or something. People just can't get some water or coolant and get home. That's mostly what turns people off Evan's for street cars.
02-23-07, 03:55 PM
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Originally Posted by Mahjik
IMO, that's not Evan's strong point. IMO, Evan's strong point is the lack of pressure it requires over conventional coolant/water mix. The less stress you can put on the cooling system, the better.
However, Evan's just isn't as practical in the odd case of a blown hose or something. People just can't get some water or coolant and get home. That's mostly what turns people off Evan's for street cars.
However, Evan's just isn't as practical in the odd case of a blown hose or something. People just can't get some water or coolant and get home. That's mostly what turns people off Evan's for street cars.
Also, I'm not sure that it is correct to say you can't mix evans with water if you are in a pinch. They say not to on the container but that is because it defeats the good points of evans. Isn't Sierra coolant just basically Evans with water mixed in? (Propelene Glycol) Read this link: http://archives.glastar.org/0005/msg00071.htmlIn a few years you might only be able to get propelene glycol based coolant. Ethylene glycol is going the way of freon and lead many other toxic consumer products.
Right now I am running evans with standard oem caps. I've read that you can take the rubber out of the fill cap and run at 0 pressure. Because of my slight o-ring problem I've been worried about losing coolant out the cap from the extra exhaust gases going in but I wonder. Maybe I should try taking the rubber out and just see what happens. I have an extra mazda cap that I mothballed earlier last year in favor of a new mazda cap which replaced it. I'll just bring some extra coolant along and take if for a short run using a rubber free cap. Anyone have any opinions on this?
Hey as far as being stuck on the road without coolant, I think it is a small price to pay for the benefits of evans to just keep some extra evans in the car. Hell I know guys who are so paranoid that they keep a couple of extra rotor housings in the trunk just in case. lol.
Last edited by Silverstone; 02-23-07 at 04:09 PM.
02-23-07, 03:59 PM
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Originally Posted by Karack
i will take the next 10 engines i break down and let you know my findings but i will bet that just about every 180 bolts will still be torqued to min.
02-23-07, 04:22 PM
#24
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Originally Posted by DaleClark
I've been an FC guy for a LOOONG time before I got my FD, and cooling seal failures aren't near as common on the FC as the FD. Most coolant seal failures on the FC are attributed to overheating by the owner - car busts a coolant hose, guy keeps driving kind of thing.
The big problem on the FD is Mazda designed the car to run MUCH hotter. FC's typically run at thermostat opening temp - about 80 deg. C. A stock FD will EASILY get into the 100 deg. C range on a warm day - the stock thermoswitch won't kick the fans on until 107 or so, which IMHO is CRAZY hot. Also, many FD's run higher pressure radiator caps, which puts more pressure on the whole system. Just not good.....
Dale
The big problem on the FD is Mazda designed the car to run MUCH hotter. FC's typically run at thermostat opening temp - about 80 deg. C. A stock FD will EASILY get into the 100 deg. C range on a warm day - the stock thermoswitch won't kick the fans on until 107 or so, which IMHO is CRAZY hot. Also, many FD's run higher pressure radiator caps, which puts more pressure on the whole system. Just not good.....
Dale
At the track one day, looked at an FC (non-turbo) and I think the oem radiator was huge compared to my FD ... much more frontal area. Even Mazda overheated an FD at the track, and redesigned the intake and cooling ducts in 1999. See SAE article at bottom of link (rest is a good read too):
http://www.rx7.net.nz/newrx7.htm
02-23-07, 06:36 PM
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instead of just guessing about the presence of or effects of electrolysis why not go out get your meter and measure it in the coolant fill neck?
warm the car up a bit
open cap
put meter in ac volt range
put one lead on battery -
other one in the coolant but not touching the sides
warm the car up a bit
open cap
put meter in ac volt range
put one lead on battery -
other one in the coolant but not touching the sides