cp1

ive been reading about this and i have yet to be convinced that the ast actually does a good job of anything well. The first and second gens didnt have them and without dire results either so im wondering if those of you who have done the elimination have noticed any ill-side effects?

and for everyone else please discuss the advantage or disadvantages of your ast. im just trying to get down to the reasons that mazda may have added it.

scrubolio

iTrader: (8)

mines gone, cooling is fine, just make sure to burp/eliminate all air bubbles in your system.

and do a search (check faq), or put your flame suit on?

cp1

yes dont worry i have done a lot of searching and found some good stuff. ive also ready pretty much everything on the subject. but i want peoples input and more specifically like i mentioned im trying to get to the very reasons mazda may have added it. Like was it added because people werent burping the system? etc.

GARCO MOTORWORKS

I removed mine many years ago with no problems .The down side with them is they can break and leak fluid without knowing it .Plus with it there are more hoses and clamps to fail .

gracer7-rx7

iTrader: (16)

I think this is the reason. Someone correct me if I'm wrong...

Mazda (and other manufacturers) use an AST in the FD b/c of the angle that the radiator is mounted. The other gens had it mounted vertically with a fill cap at the top. Air would rise to the top of the rad and you could bleed it out the top. With the angle at which the FD rad is mounted, it became difficult to get air out of the system w/o having an AST (air separation tank).

You can google "air separation tank" to get more info if you like.

cewrx7r1

iTrader: (2)

Except none of the AST hoses go to the top of the raditor where you say there is trapped air. They go to the overflow tank, bottom of the radiator, and to the second filler cap. The laters become the overflow and air seperator all in one.

cp1

yes but what is so uniquely different about the FDs setup that they would have invented the ast in the first place. if overheating and airbubbles were major issues they would have added it to late model 2nd gen cars hoping to fix these known issues then under warranty. i mean the 91 cars were still under warranty in 93 and if was such a common thing they would have had a recall put out to retrofit the more recent 2nd gens with an ast, that is to say if the ast did much of anything at all. so why go through all the trouble of adding it only on one model of car? can anyone with an rx8 chime in to say if they have an AST?

bryant

AST

air seperation tank.


The tank's purpose is to remove air bubbles in the coolant system.

so if you dont have one you will have to make sure you have burped the system good to remove all air bubbles.

cp1

Ya i think we all pretty much understand what it means and what its supposed to do.

bryant

so you understand but still ask stupid questions??

http://www.fd3s.net/coolant_tank_elimination.html

look at #2 from Date: Thu, 6 Aug 1998 21:35:28 EDT
From: KAWalanski@aol.com

and again if its only needed after you change you coolant than why would mazda do a recall that could cost them thousands.

just get one of these https://www.rx7club.com/3rd-generation-specific-1993-2002-16/radiator-cap-funnel-eliminate-air-bubbles-342309/ then you dont need an ast, and you reduce the risk of possible future problems.

cp1

Theres nothing stupid about anything im asking here!

Yes ive read that many times and he leaves it as an open-ended question. his post is more of a hypothesis and not that of an observation. there is nothing definitive in his post. i did find the link you provided to the funnel especially useful thank you. again my question is why on the the fd only? ive been looking through everything on the rx8 cooling system and they do not seem to use it either so now im looking for any major changes to the cooling system over that of the fd and cant seem to locate anything specifically. so my best guess is that it was mazda's best guess at a possible solution that may not have been entirely effective at doing much of anything.

If it is needed after a coolant change and this was a major contributor to engine failure you better believe they would have recalled 2nd gens still under warranty to add it. as the cost to retrofit would certainly be lower than engine replacement.

Im still going to be looking into this

Mahjik

iTrader: (1)

lol, there are a lot of improvements car companies do to a later model which don't get retro-fitted to their older models.


Many people have run without the AST and not had any problems. The main issue is that it makes burping the system a little more difficult. If you don't know how to burp the system completely, then I would suggest leaving the AST on the car. While I believe AST's are useful, I don't believe the FD has the ideal location for one. If you look at the old Rotary Lemans car, you'll see an AST but it's much higher in the system. At that height, it's much more effective but something like that wouldn't be quite possible in the FD engine bay.

cp1

True but these improvements arent usually ones that necessarily eliminate the likelyhood of engine failure though

and your right about about the height needed to properly burp the system the inlet and out let should be the highest points of the cooling system. outlet meaning a vent somewhere, like how most of us use the throttle hose.

and yes i agree with everyone here that properly burping a system is definitely a good idea (which you guys should not assume i do not know how to do!) but was the major difference in design that would have caused mazda to add an AST on the FD the configuration of the Radiator? i think so because it is so low and at an angle that it could be prone to trapping a lot of small air bubbles. i noticed when removing my rad that after draining it in the car their was still a lot of coolant left inside that could only be drained by turning it on its sides. these bubbles would of course go into the block and cause heating damage. the solution? relocate the rad vertically and thus making it much higher in the process.

obviously you still have to take care to burp the system thoroughly. but i think in all of my observation that the AST was a product of the design of the cooling system because of the design of the car. the engine design has not changed nor has the theory behind it. the only thing that is truly different on the FD is the location of the rad. and thus the AST.

BigWillieStyles

the S7 and S8 models sold in Japan and Australia got the same plastic ASTs.

bryant

because they were smart enough to take the user out of the user error.

most people aren't smart enough to check-change there oil so Mazda got smart and said hey there dumb asses and put the ast on the car to keep the likelihood down to a blown motor from some dumbass that says hey i can change the coolant thats easy and forgets to bleed the system.

cewrx7r1

iTrader: (2)

Just because a car has some gadget, does not mean it is needed or works properly. Look at all the recalls of things that fail.

If you ever worked on a lot of cars, you should have discovered many cases of poor or just stupid engineering.

After all, engineers and companies are run by people and they do make mistakes.

KaiFD3S

iTrader: (37)

Mine has been deleted forever and no problems here.

FD3S2005

iTrader: (11)

kai you dont count since you have a super car

TRISPEEDFD3S

iTrader: (26)

HAHAHAHAHAAHAHAHAAH! I tell him all the time....

CantGoStraight

Didn't the first and second gens have radiators with there caps/filler neck right on the radiator? (My guess as to why they didn't have an AST) Many people have eliminated them withoutdire results, just makes burping the system take a bit longer in some cases.