Ast Tank Elimation?
06-07-08, 12:09 AM
#1
Greasy bastards..
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Ast Tank Elimation?
time to eliminate the ast tank, just curious about the 1986 filler neck oem part#, i found the one from mazda trix, but this is no good at the dealer, the dealer's break down of these parts is very poor, so far 2 wrong parts, man i didn't think it would be this hard for a dealer to find this part, can't wait to try & order something difficult from them. thanks
06-07-08, 12:21 AM
#2
Call Ray Crowe at Malloy Mazda. Describe what you want, he'll have it for ya at the best price you can get for a new OEM part.
(888) 533-3400 or hmkparts@aol.com
(888) 533-3400 or hmkparts@aol.com
06-07-08, 12:37 AM
#4
Call Ray Crowe at Malloy Mazda. Describe what you want, he'll have it for ya at the best price you can get for a new OEM part.
(888) 533-3400 or hmkparts@aol.com
(888) 533-3400 or hmkparts@aol.com
Ray Crowe is the men! His a great guy to deal with
06-07-08, 10:46 AM
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I would strongly recommend you dont remove your ast... This is a very important piece to have on your car.. If you dont like the look then you can purchase one from one of many aftermarket companies.. The ast removes air from the cooling system, without it you run a high chance of getting air bubbles in the engine and causing a hot spot to create and engine failure.. Do not remove your ast...
06-07-08, 10:58 AM
#6
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You can safely remove the AST, but you will lose some capacity in your cooling system. It has been done without ill effects many times. Look here:
http://fd3s.net/coolant_tank_elimination.html
http://fd3s.net/coolant_tank_elimination.html
06-07-08, 11:02 AM
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time to eliminate the ast tank, just curious about the 1986 filler neck oem part#, i found the one from mazda trix, but this is no good at the dealer, the dealer's break down of these parts is very poor, so far 2 wrong parts, man i didn't think it would be this hard for a dealer to find this part, can't wait to try & order something difficult from them. thanks
comes with O-Ring. I paid $40.44 and $3.08 for the o-Ring Will sell for $25.00 +
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06-07-08, 11:22 AM
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i have read alot of info on fd3s.net alot of it is good, i dont think that ast removal is one of those, rotarymandan have you done this mod on your own car? Im just giving imput if you dont seriously damage your motor then you are lucky, Is that a chance you are willing to take.. im sorry but i dont just like to rebuild motors
06-07-08, 12:01 PM
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i have eliminated an AST tank, my car always gets a good ragging and it never let me down after i did it, it's been done many times before - with no problems and those scary air bubbles never affected peoples car... dont know why but i think its just a rumor, all ast bullshit...rx7 is the only car that people install an ast to....
06-07-08, 01:07 PM
#10
The FD comes with an AST from factory. With the sensitivity to heat inherent to rotaries, any air bubbles are an unnecessary decrease in cooling system efficiency.
Don't propagate incomplete information.
Have people removed them and not had a failure caused by the lack of an AST? Yes.
Have people had the factory AST break and expel the engines coolant all over the road? Yes.
Have people replaced their factory plastic AST with an after-market part for reliability and to maintain the function of an AST? Yes.
06-07-08, 02:53 PM
#12
I ran with no AST for 5+ years. It in my experience it does nothing significant. The only downsides are an insignificant loss in cooling capacity(can be remedied by installing a larger radiator which you should anyway) and it makes it slightly more difficult to purge the system of air after a coolant change.
06-08-08, 10:51 AM
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Have people removed them and not had a failure caused by the lack of an AST? Yes.
because they didnt purge the system of air after a coolant change
Have people had the factory AST break and expel the engines coolant all over the road? Yes.
because they HAD an AST
Have people replaced their factory plastic AST with an after-market part for reliability and to maintain the function of an AST? Yes
of course it works as good as without it..
mate just want to say that i'm all new to this but the amount of stuff i read before i done anything on my car , written by people much more compentent then you would make me have right to share this information.
heres some info(just googled it)
because they didnt purge the system of air after a coolant change
Have people had the factory AST break and expel the engines coolant all over the road? Yes.
because they HAD an AST
Have people replaced their factory plastic AST with an after-market part for reliability and to maintain the function of an AST? Yes
of course it works as good as without it..
mate just want to say that i'm all new to this but the amount of stuff i read before i done anything on my car , written by people much more compentent then you would make me have right to share this information.
heres some info(just googled it)
Date: Thu, 6 Aug 1998 21:35:28 EDT
From: KAWalanski@aol.com
I occasionally get into a compulsive rut which is difficult to shake while my old brain struggles to understand something without my conscious intervention. It has happened again this time with the Air Separator tank on my '93. Since buying my car last year, I cannot quiet this little voice in my mind which keeps asking what the air separator tank's purpose is, why it is needed, and how it functions, and it it has anything to do with the significant number of engine failures apparently due to overheating. I have assumed that Mazda needed this additional piece of plumping in the cooling system, otherwise it would not be there. Here are some questions, thoughts, findings and perhaps even conclusions which I've reached, so far, and the results of some experimenting.
1. The system seems to be designed to eliminate tiny bubbles from the coolant, not to bleed the system of air. I've taken a look at the coolant at the top of the air separator tank and found it cloudy. I took a sample of the cloudy coolant and it became clear, like typical anitfreeze, after a week of sitting.
2. The presence of these tiny bubbles in the cooling system will significantly reduce the heat transfer efficiency of the coolant. Mazda engineers must have recognized this during the 3rd gens development and added the air separator tank to eliminate (reduce?) the problem. I have never seen an air separator tank on any other car. Has anyone else? Does anyone know of any other car which has an air separator tank?
3. So, where do these tiny bubbles come from? The only place I can figure is that it is the gas (essentially atmospheric gases) dissolved in the water and/or coolant when the cooling system is freshly replaced. The concentration of gas in a liquid is inversely proportional to temperature, so the higher the temp, the smaller the amount of gas which can be dissolved in the liquid, in this case the coolant/water mixture. But once these gases are removed from the coolant, the air separator tank would serve no useful purpose until the next time the coolant is changed and the dissolved gases again needed to be eliminated. Or, is there some other source of gas?
_________________
Date: Wed, 10 Dec 1997 20:56:57 -0500
From: Rob Robinette (robinett@postoffice.dca.net)
Here's how to remove the small black coolant "air separation tank" that's bolted to your 3rd gen's intercooler. First, why would you want to eliminate the air separation tank? Well, it has a tendency to explode and dump all your coolant at inopportune times, it blocks some airflow through the intercooler and eliminating it frees up some space in the engine compartment. Many people on the list have done this with no apparent cooling system problems.
You will need two things to eliminate the tank. First one is the 1986 RX-7 "Radiator Cap Neck" with the overflow tube, part # 15-17YA-N326, $30.20 from Mazdatrix (don't be confused by the name, the radiator cap neck doesn't attach to the radiator, it's the radiator cap located on the engine). You will also need a 3/8" hose coupler and two hose clamps. Home Depot and Pep Boys sells a 3/8" "Camel" Hose Repair Kit ($4). It's in the tool area with the air tool accessories. The part # on the front of the package is 52-465, the number on the back of the package is 657465 A.
The radiator cap neck swap is easy but be careful not to drop the round rubber o ring that will probably come up with the old neck. I dropped it down onto the engine compartment floor pan. I had to pull it loose to find the o ring (I was going to pull the pan anyway to take the plastic air restrictors in the nose air inlet out).
The next step is to join the hose that goes into the bottom of the air separator tank with the one that goes into the middle of the tank. The hose from the bottom of the tank will not have to run below the intercooler anymore so it's best to route it so that it comes up from the bottom of the engine directly below the radiator cap neck that you just swapped out. Bring this bottom hose directly up to the hose that was connected to the middle of the tank and couple them together using the 3/8" brass coupler that came in the hose repair kit. Don't forget to put the hose clamps on before you join the hoses.
The last step is to connect the air separator tank's overflow tube to the tube on the new radiator cap neck. This hose goes to the coolant overflow tank (in front of the right front wheel well). Just run the hose where you want it and cut it to fit. I lost about 1/2 a quart of coolant when I did this mod. I placed a medium sized bowl where the stock air box used to be to catch the fluid. Be sure to top off the coolant when you're finished. The mod isn't nearly as complicated as it sounds and there are a few pictures of the mod out there on someone's web site. Good luck.
From: KAWalanski@aol.com
I occasionally get into a compulsive rut which is difficult to shake while my old brain struggles to understand something without my conscious intervention. It has happened again this time with the Air Separator tank on my '93. Since buying my car last year, I cannot quiet this little voice in my mind which keeps asking what the air separator tank's purpose is, why it is needed, and how it functions, and it it has anything to do with the significant number of engine failures apparently due to overheating. I have assumed that Mazda needed this additional piece of plumping in the cooling system, otherwise it would not be there. Here are some questions, thoughts, findings and perhaps even conclusions which I've reached, so far, and the results of some experimenting.
1. The system seems to be designed to eliminate tiny bubbles from the coolant, not to bleed the system of air. I've taken a look at the coolant at the top of the air separator tank and found it cloudy. I took a sample of the cloudy coolant and it became clear, like typical anitfreeze, after a week of sitting.
2. The presence of these tiny bubbles in the cooling system will significantly reduce the heat transfer efficiency of the coolant. Mazda engineers must have recognized this during the 3rd gens development and added the air separator tank to eliminate (reduce?) the problem. I have never seen an air separator tank on any other car. Has anyone else? Does anyone know of any other car which has an air separator tank?
3. So, where do these tiny bubbles come from? The only place I can figure is that it is the gas (essentially atmospheric gases) dissolved in the water and/or coolant when the cooling system is freshly replaced. The concentration of gas in a liquid is inversely proportional to temperature, so the higher the temp, the smaller the amount of gas which can be dissolved in the liquid, in this case the coolant/water mixture. But once these gases are removed from the coolant, the air separator tank would serve no useful purpose until the next time the coolant is changed and the dissolved gases again needed to be eliminated. Or, is there some other source of gas?
_________________
Date: Wed, 10 Dec 1997 20:56:57 -0500
From: Rob Robinette (robinett@postoffice.dca.net)
Here's how to remove the small black coolant "air separation tank" that's bolted to your 3rd gen's intercooler. First, why would you want to eliminate the air separation tank? Well, it has a tendency to explode and dump all your coolant at inopportune times, it blocks some airflow through the intercooler and eliminating it frees up some space in the engine compartment. Many people on the list have done this with no apparent cooling system problems.
You will need two things to eliminate the tank. First one is the 1986 RX-7 "Radiator Cap Neck" with the overflow tube, part # 15-17YA-N326, $30.20 from Mazdatrix (don't be confused by the name, the radiator cap neck doesn't attach to the radiator, it's the radiator cap located on the engine). You will also need a 3/8" hose coupler and two hose clamps. Home Depot and Pep Boys sells a 3/8" "Camel" Hose Repair Kit ($4). It's in the tool area with the air tool accessories. The part # on the front of the package is 52-465, the number on the back of the package is 657465 A.
The radiator cap neck swap is easy but be careful not to drop the round rubber o ring that will probably come up with the old neck. I dropped it down onto the engine compartment floor pan. I had to pull it loose to find the o ring (I was going to pull the pan anyway to take the plastic air restrictors in the nose air inlet out).
The next step is to join the hose that goes into the bottom of the air separator tank with the one that goes into the middle of the tank. The hose from the bottom of the tank will not have to run below the intercooler anymore so it's best to route it so that it comes up from the bottom of the engine directly below the radiator cap neck that you just swapped out. Bring this bottom hose directly up to the hose that was connected to the middle of the tank and couple them together using the 3/8" brass coupler that came in the hose repair kit. Don't forget to put the hose clamps on before you join the hoses.
The last step is to connect the air separator tank's overflow tube to the tube on the new radiator cap neck. This hose goes to the coolant overflow tank (in front of the right front wheel well). Just run the hose where you want it and cut it to fit. I lost about 1/2 a quart of coolant when I did this mod. I placed a medium sized bowl where the stock air box used to be to catch the fluid. Be sure to top off the coolant when you're finished. The mod isn't nearly as complicated as it sounds and there are a few pictures of the mod out there on someone's web site. Good luck.
06-08-08, 05:17 PM
#15
The Dirty Mexican
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The previous owner of my FD performed the AST elimination mod. He ran it like that for an unknown amount of time, and I've ran it for another 3+ years with zero overheating issues. As Rotary Experiment Seven mentioned, the only downside I've noticed is that it does make it slightly more difficult to purge the system, and even that's not such a big deal.
06-09-08, 11:49 AM
#16
Greasy bastards..
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i appreciate all the info on ast elimation, i will be removing it for sure, all i really need is the oem mazda# for the 86 filler neck, i would order from mazdatrix, but as u can see i'm in canada, probably 2 weeks for the part, oem stuff 2 days, just the mazda break down doesn't list this part
06-09-08, 02:54 PM
#17
Original Gangster/Rotary!
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I used to be part of the pro-AST camp, but have since switched sides. Been running without one for years, and we're so sure of the safety of the elimination that we perform it on many of our customer's cars that have fresh motors that we warranty
06-10-08, 12:09 AM
#18
Buddy, Your illiterate posting proves to me that you need to lay off. Your first post said "all ast are bullshit."
This is incomplete information. So I will stand by my statement. Oh, and spell-check is your friend, and perhaps grammar check too. Don't be a tool.
By the way, A post that says "I rag on my car day in and day out and I have never had a problem, and because of my experience with ONE vehicle; all AST's are bullshit."
There is more than one logical fallacy here. If you don't know what that means, then perhaps you should go ask someone more competent than yourself to explain it to you. You gave no information, just a broad statement based on little experience. And then you feel justified in picking apart my post... which happens to have at least more experience behind it than yours.
In conclusion, I will state that your original post was incomplete. You cannot refute this. So where did you get the gumption to call me incompetent?
Next.
Edit -
Ironically enough, I will not be running an AST on my next engine build. I was merely pointing out that explaining only one side of an answer is more of an opinion and not a complete answer.
Last edited by Monkman33; 06-10-08 at 12:18 AM.
06-10-08, 02:33 PM
#19
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after i read what you said ...well i think i hit the spot 
by writting your last post you have just proven your incompetence
read my post carefuly ...
this is my opinion about it, i said i think and i said something about MY car , that doesnt mean i'm trying to play smart, and like everybody else shared my opinion,
do i have to explain this one as well?
anyway you boring me now next time please read and UNDERSTAND
btw:
talking about my grammar wasnt the right thing mate, dont try to play smart, i've been speaking this language for less then two years...
by writting your last post you have just proven your incompetenceread my post carefuly ...
i have eliminated an AST tank, my car always gets a good ragging and it never let me down after i did it, it's been done many times before - with no problems and those scary air bubbles never affected peoples car... dont know why but i think its just a rumor, all ast bullshit...rx7 is the only car that people install an ast to....
06-07-08 10:22 AM
06-07-08 10:22 AM
Originally Posted by sickboy
mate just want to say that i'm all new to this but the amount of stuff i read before i done anything on my car , written by people much more compentent then you would make me have right to share this information.
anyway you boring me now
next time please read and UNDERSTAND btw:
talking about my grammar wasnt the right thing mate, dont try to play smart, i've been speaking this language for less then two years...
06-10-08, 02:55 PM
#20
I've eliminated mine as well with no adverse effects so far. 
In my case, I had a Pettit AST which began leaking at the pressure relief cap...multiple times. I decided it was time to eliminate it, and I couldn't be happier. Really, when you think about it, once the air is out of the system the AST is just another place for coolant to leak from.
As long as the system is air tight and full, you should be fine eliminating it (and should not have any trouble with air getting into the system).
In my case, I had a Pettit AST which began leaking at the pressure relief cap...multiple times. I decided it was time to eliminate it, and I couldn't be happier.
Really, when you think about it, once the air is out of the system the AST is just another place for coolant to leak from.As long as the system is air tight and full, you should be fine eliminating it (and should not have any trouble with air getting into the system).
02-14-21, 01:14 PM
#21
I replied to a really old thread, but I thought I should do it to a newer thread as well. Here's my two cents:
The issue no one thinks about is backpressure of coolant through the radiator at high RPM/coolant velocities.
If you eliminate the AST, the radiator cap is now on the high pressure outlet of the water pump. Due to pressure loses from the friction of the radiator lines and coolant going through the radiator, higher pressures can build up at the outlet. At high RPM, the pressure in that line will reduce the effective strength of the spring pressure in the radiator cap. If you have 16 psi, it will open at a much lower pressure.
This is important because it will reduce the boiling point of your coolant, making it more easy to overheat your engine.
By moving the radiator cap to a tank that sees significantly less flow, the cap works at its intended pressure. Removing bubbles from the coolant is just a side benefit.
Dan
The issue no one thinks about is backpressure of coolant through the radiator at high RPM/coolant velocities.
If you eliminate the AST, the radiator cap is now on the high pressure outlet of the water pump. Due to pressure loses from the friction of the radiator lines and coolant going through the radiator, higher pressures can build up at the outlet. At high RPM, the pressure in that line will reduce the effective strength of the spring pressure in the radiator cap. If you have 16 psi, it will open at a much lower pressure.
This is important because it will reduce the boiling point of your coolant, making it more easy to overheat your engine.
By moving the radiator cap to a tank that sees significantly less flow, the cap works at its intended pressure. Removing bubbles from the coolant is just a side benefit.
Dan
02-18-21, 03:22 AM
#22
^ For posterity, in case someone else comes across it, this is wrong. We’ve never thought about the issue because it’s not an issue.
Dan’s double post and replies at #42 ——> https://www.rx7club.com/3rd-generati...iminate-53559/
Dan’s double post and replies at #42 ——> https://www.rx7club.com/3rd-generati...iminate-53559/
Last edited by Sgtblue; 02-18-21 at 03:30 AM.
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02-18-21, 07:35 AM
#23
Racecar - Formula 2000
I replied to a really old thread, but I thought I should do it to a newer thread as well. Here's my two cents:
The issue no one thinks about is backpressure of coolant through the radiator at high RPM/coolant velocities.
If you eliminate the AST, the radiator cap is now on the high pressure outlet of the water pump. Due to pressure loses from the friction of the radiator lines and coolant going through the radiator, higher pressures can build up at the outlet. At high RPM, the pressure in that line will reduce the effective strength of the spring pressure in the radiator cap. If you have 16 psi, it will open at a much lower pressure.
This is important because it will reduce the boiling point of your coolant, making it more easy to overheat your engine.
By moving the radiator cap to a tank that sees significantly less flow, the cap works at its intended pressure. Removing bubbles from the coolant is just a side benefit.
Dan
The issue no one thinks about is backpressure of coolant through the radiator at high RPM/coolant velocities.
If you eliminate the AST, the radiator cap is now on the high pressure outlet of the water pump. Due to pressure loses from the friction of the radiator lines and coolant going through the radiator, higher pressures can build up at the outlet. At high RPM, the pressure in that line will reduce the effective strength of the spring pressure in the radiator cap. If you have 16 psi, it will open at a much lower pressure.
This is important because it will reduce the boiling point of your coolant, making it more easy to overheat your engine.
By moving the radiator cap to a tank that sees significantly less flow, the cap works at its intended pressure. Removing bubbles from the coolant is just a side benefit.
Dan
While you are technically correct, in practice, this is, as Sgtblue says, a non-issue IN MOST APPLICATIONS. I "could" see in an application where the water pump was very efficient and the hoses, radiator were too restrictive, plus there was no restriction exiting the block, etc., that this would be correct. The WP is placed where it is, pressurizing the coolant in the engine, to raise the boiling point a few degrees and prevent localized boiling as high flow creates localized turbulence. Usually, however, a restrictor or thermostat at the block exit creates the pressure rise, and since the pressure-relief radiator cap is after that restriction, it sees little if any pressure rise due to the WP.
So, in practice, if the system is designed properly, this is a non-issue.
Last edited by DaveW; 02-18-21 at 07:38 AM.
02-18-21, 08:48 AM
#24
While you are technically correct, in practice, this is, as Sgtblue says, a non-issue IN MOST APPLICATIONS. I "could" see in an application where the water pump was very efficient and the hoses, radiator were too restrictive, plus there was no restriction exiting the block, etc., that this would be correct. The WP is placed where it is, pressurizing the coolant in the engine, to raise the boiling point a few degrees and prevent localized boiling as high flow creates localized turbulence. Usually, however, a restrictor or thermostat at the block exit creates the pressure rise, and since the pressure-relief radiator cap is after that restriction, it sees little if any pressure rise due to the WP.
So, in practice, if the system is designed properly, this is a non-issue.
So, in practice, if the system is designed properly, this is a non-issue.
My biggest concern is that this issue would be next to impossible to diagnose without pressure taps, so it could be cause for concern, and maybe just a small concern, but it shouldn't be dismissed out of hand with purely circumstantial evidence. I mentioned in the other thread that I am willing to help measure to see what can be seen. I have the sensors and equipment to datalog, I just don't have an FD handy to do so.
Dan
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