Can I just cap off where the hose goes from the filler neck to the ast? Is the ast really nessisary? Cause After FMIC install.. noplace to put it and its the stock pos..

Matt

 

theres quite a bit of debate as to wether you should keep or get rid of the AST. There is a mod to get rid of it ( do a search) but after I read that someone took a stock AST apart and found its internals to be a specific and suprisingly complex design I thought to myself that I'd keep mine, anyway, a FMIC normally frees room up to put it somewhere??

 

I didn't notice a difference without it however I have since replaced the AST with an aftermarket one. The debate goes on...

 

You can remove the AST. However, that means you'll have less coolant in your system (not a huge deal) and it's more of a pain to burp the system.

The AST is just another failsafe for the car. However, Mazda's LeMans car used one, but it's mounted much higher which makes it more effective. If they use it on a race car, I think it's worth using it on my street car.

 

I agree with Mahjik. But I wanted to add my observations. The AST is to assist with burping the car when the radiator is in the stock location. If you have a front mount then the radiator is upright and the AST surves less of a purpose.

 

I've considered eliminating the AST for the same reason as you Godzilla-T78, no good place to put it.

I remember reading the exact opposite of the magical mojo that's inside the stock AST. People talk of "baffles" inside it that aid in air separation, but I remember reading that someone opened it up and it was just a hollow container. There are no baffles of any kind in the Pettit alum one, that's for sure. I guess I should dissect the leaking stock one in my parts bin.

Mahjik (or anyone else),

Is it true that for the AST to be effective, it must be the highest point in the cooling system?

 

Most effective yes. However, the stock location, while not as high as Mazda probably would have liked, still helps in removing air from the system.

 

This may have been discussed before, however, I thought I would share.

I had the bolt come undone that holds my AST to the IC. When it happened, the AST fell MUCH lower into the engine bay (about 6-8" I'm guessing). Just this alone caused my engine temps to fluctuate greatly. Additionally, I was running about 5 degrees warmer than normal.

I'm not certain how this translates to AST removal, however, the higher I can mount it in the engine bay, the better.

 

unlike the lemans unit, the stock fd ast just gets a trickle of flow. it has no baffels.

ok to remone on healthy engine. just be careful when burping system, and check level in neck every couple weeks.

to eliminate, must have removable top of filler neck. use 2nd gen filler top.

if bypass hose is used, put a .06" pill in it, or just plug nipples with short hose segments (not weak rubber vacuum caps. This will make the top of the filler neck act like a mini ast.

 

Well.. I am moving batter to rear of car due to NO ROOM WITH FMIC.... So I have no where to mount so I figured Id remove it, if I kept it anyone have pics of where they put theres and how they did it?

Matt

 

a fc neck would do you good.

my buddy and i was thinking one day why there is an ast and we noticed it keeps blown motors running. so could the ast be there to keep blown cars running to make it back to the shop? i dunno tell me your input.

 

Correct, there are no baffles in the stock AST. We opened one up not long ago.

 

Most FD's that we work on at the shop of factory AST's still installed. It's usually one of the first upgrades we inform the customer of. The factory equipment just sucks to be honest. There are many aftermarket company's that offer replacement units for a relativly cheap amount. Get off the wallet.

Regards,
-Markus

 

I dont think the issue here is cost.

Noticed your sig. I take it you are quoting yourself. Are you for real?