Mazda put it there to get rid of the air in the system, if you delete it, you can trap air bubbles in the engine and it can develop hot spots which could lead to o-ring failure, but a lot of people swear by it, however, Mazda engineers put it there for a reason.

 

i don't "swear by it" but i did use it on my FD. I kinda did it to make more room in my engine bay and just eliminate the AST which cracked. It didn't seem to give me problems and I had it on for a good 40-50K before my car was stolen.

 

don't delete it
just spend the extra few bucks and don't be cheap

if you have heard any people say that there is a possibility that it is dangerous to delete it why would you risk it unless you don't care about your car or you are stupid?

I have heard many people say that it is needed
Pettit sells an aluminum one go get it!

 

Its nothing more than a cheat for your cooling system. You don't need it. And you won't get air in your cooling system if you burp it correct. Get a 2nd genn filler neck and bolt it on. It works fine.

 

Yea the Mazda engineers put two cats and smog pump on the car for a reason too. I just can't figure out what it was???

 

AHAHAH yea musta been some reason...too bad most FD owners can't seem to find it.

 

Most of the reason I got an aluminum one is so the system held about a quart more coolant than if I had removed it.

With the questionable cooling system as it is, why reduce the capacity of the system?

 

I work at a racing school with 24 rortary powered racecars all running air separator tanks. However the tank should be connected to the highest points in the cooling system, i.e. the top of the radiator and the top of the engine. The problem is that the fd picks up coolant/air bubbles from the bottom of the radiator and halfway down the filler neck. Air rises in water/coolant. So basically the stock AST never really has a chance to scavenge any air out of the system. Go with the 2nd gen filler neck and remove the AST. The 2nd gen filler neck with scavenge air out of the system as it will be the highest point in the system.

 

I am removing it. I had the Pettit ast but I decided that after the m2 large smic that I needed the room so here I am

 

I have deleted mine too... the key is MAKE SURE you get the air out when you refill and use the 2nd gen black plastic fill neck. I agree with Ernie... it's on there just to help you out and make it easier to get the air out. Your car will not explode if you don't have it. How do you think that millions of other cars on the road get by without one?

Brian

 

I had my AST eliminated w/o any problems. Also it's been close to high 90's close to 100 deg C. in SoCal, and with large Koyo and fan mod 'on', temperature is always in control in the 86-87 deg. range.

As for people fearing the inefficiency for bleeding air out of the system putting on the T2 filler neck, you can drill couple more tiny holes at your thermostat to help bleed out air faster.

Timmy

 

i tossed my ast long times ago. no problems here. cooling is fine. now i have all the room for an ic.

 

I'm in the middle of doing my AST elimination right now, but have a question or too. I saw on either the Rob Robinette or Lightning in a World of Thunder site they removed the hoses to the expansion tank rather than just relocating the hoses. My question is when relocating the hoses, did anyone trim or cut these hoses for proper fitment? I'd rather not have to cut hoses ifI don't have to, though I can always go buy more hose..

 

Make the hose that goes from the black plastic filler neck down to the bottle as straight and short as is practical. Avoid having a loop that hangs down like a sink trap.

I was just trying to figure out why my system wasn't sucking back from the overflow right, and Dave at KDR suggested that it -could- be due to that problem. I shortened my much too long hose, and after one test run, it seems to be helping. Hard to say 100% without more testing, but looks good so far.

Brian

 

Isnt the stock fc filler neck made out of Plastic?
it is prone to crack then