Considering myself lucky - failing AST
 

Doing the reliability mods and found myself really lucky to change the AST before it disintegrated.

Just a slight twist taking the hose off and the plastic just crumbled. ​​​​​​​

https://cimg4.ibsrv.net/gimg/www.rx7...216b44730b.jpg
https://cimg6.ibsrv.net/gimg/www.rx7...79f17be186.jpg

Until some sort of ACTUAL proof exists that the ast does anything, I will always suggest people delete them as part of the reliability mod package.

even if some sort of proof DOES exist that they do anything, I will still suggest people delete them anyway. There's wayyyyy too many people running without them (including myself) on too many different set ups, with too many different power levels, in too many different environments for any sort of proof to disprove that it does nothing.

it's clutter in the bay that takes up valuable real estate and adds what...... 6 attach points of potential failure? The only noticeable benefit is the bling factor. It's one more thing to just look at...

Good catch! I still need to change mine too but luckily the stock one is holding up. I'm going to have it powdercoated matte black for a more stealthy appearance.

Edit

This. Just delete the fucking thing.

People act like the AST is some kind of black box. It is just there to help with coolant bubbles that's it, so delete it and make sure to burp the coolant system properly and call it day. If you have n aftermarket temp gauge you will see that removing the AST makes zero difference.

^Yep. If the car was near-stock, it makes sense to just go with an aluminum AST. They don't cost that much, are easy to install, and they work. For a newbie user it's much easier to just swap out with an aluminum one than block off the 2 nipples properly, swap out the rad cap, etc.

Also, people with newer engines that don't have the bolt-on radiator cap neck that's on the thermostat housing this is much easier than tracking down a good used T-stat housing and swapping that out.

That said, I've been running no AST for YEARS in Florida heat with zero problems, even with a stock radiator back in the day.

Dale

Geez, I never kne w buying and replacing the OEM AST once every ten years was such a big deal :rolleyes:
Yes ,20 years ago I replaced mine with a very nicely made M2 AST after many reports of early AST failure (mostly on 93 cars right after they went off warranty). However, most all aftermarket ASTs have too large an opening at the bottom nipple allowing the coolant to race through the AST. Look at the stock tank, you will see a small restrictor at the bottom . The coolant is supposed to be quiescent in the tank allowing the bubbles to come out of solution and rise to the top, hence the large surface area at the top of the AST and the skinny bottom. I fixed that oversight on the M2 AST by pressing in a brass cauberator jet. Even though the M2 AST was the nicest looking one at the time, I still think the stock one is a better design (form follows function). For me, after 20 years of using the M2 AST, I just installed a new stock AST, I actually bought two. That puts me some where around 2039 before I’ll need to buy another one. Do you really need an AST? Probably not. Will an aftermarket one work? Yes, but not as efficiently as the stock tank. Does the stock tank look better than an aftermarket tank? Yes. On most aftermarket ones the welds usually look like someone in High School weld shop made it and the radiator caps are too large.

With all that said, what are you referring to as "working"? Working in what sense? You claim it does all those things but what proof is there that is actually happening? Very clearly there is no effect whatsoever to not having it there and it "doing" it's job. It's snake oil.... kind of like fuel magnets.

I pressed a restrictor plug the same size as the opening in the OE AST into the bottom tube of my Pettit AST when I installed it in 2004.

Experiences vary but the truth is there has been documented issues with the AST since the forum's inception. For instance, I had a stock AST fail in my 26K mile FD in 1998...


EDIT- My issue with the AST is that it's an unnecessary failure point whose benefits are non existent if the coolant system is burped properly.

IMO AST elimination is only an option if done properly...with the S5 neck and npt plugs etc. Otherwise you haven’t added any dead space or gotten rid of potential failure points. And I’ve seen a few really sketchy eliminations. Like many others I eliminated it years ago with no issues other than maybe taking a little longer to get all the air out when I annually change coolant.
That said it looks like the OP has a very stock car. He wanted to keep it that way a good metal ast. If he wanted to also keep a new stocker sitting on the shelf I’d understand.

Trying to keep as stock as possible with reliability mods!

Agreed... if he wants to keep it stock then by all means live your life. The discussion is making the car more reliable though. If you're in there doing mods, reliability or otherwise, then deleting the ast and it's entirety will improve the reliability of the car. The ast has been proven to serve no function and acts as nothing more than a "side road" for coolant to hang out and on occasion liberate itself from the engine.

Thats my whole thing on this. Leave it 100% stock or delete it as part of the reliability mod package.

I am happy this topic came up, we will be releasing our new billet AST elimination kit next week.

https://cimg9.ibsrv.net/gimg/www.rx7...cd932936a.jpeg

I'm happy this came up too! I've been looking to delete mine for some time (its currently held in the engine bay by wire ties -- ugh). That said, I've seen lots of ways to do it online, and I've not found one that's particularly complete or easily accessible. Is there an agreed-upon method that is "proper" for doing the deletion? It seems somewhat daunting, but perhaps it's one of those things that seems complex until you're doing it -- or perhaps I just wait for the Banzai kit (plug for their excellent oil pan brace here).

I'd appreciate any pointers to the most trouble-free way to do the elimination.

Thanks!

OH MY GOD!!!!!!!!!!!!!!!!!!! ive been wanting one of these forever!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!! thank you banzai!!!!

There's not much to it. Parts needed -

- 86-88 FC radiator cap pedestal and radiator cap
- O-ring under pedestal
- Coolant
- Lisle coolant funnel

Drain the coolant from the radiator. Remove the 2 10mm bolts holding the stock pedestal to the thermostat housing. Remove the AST.

Replace the O-ring under the pedestal with the new one. Bolt the new pedestal on. I like to put a little anti seize on the 2 bolts since they frequently get coolant on them and can rust/sieze in place.

Hook the hose going to the coolant overflow tank (did come from the top of the AST) to the new pedestal.

Remove the 2 small hoses that went to the AST - one goes to the bottom of the radiator, one goes to the thermostat housing. One of the hoses should reach from one nipple to the other, plumb that in.

Fill up with coolant using the Lisle funnel and make sure to get all the air out. Drive around and check the coolant level when cold the next few days, top off if necessary.

You can also block off the 2 hose ports, I had the nipple on the radiator cut off and welded shut and same for the thermostat housing. The T-stat housing could be drilled/tapped and plugged but a weld is a much better solution. I found a local welding shop that did it for like $20, much cleaner looking and it can't leak if it's all one piece.

Dale

Billet S4 filler neck officially available. Air Separation Tank (AST) (93+ RX-7)

https://cimg1.ibsrv.net/gimg/www.rx7...24d54c6cac.jpg

You can survive without your appendix, but I wouldn't recommend removing yours for spite or superstition.

Unless there's some sort of space/packaging issue in your modded engine bay, I'd just replace it with a new stock AST. They're cheap, and the new one will last until cars fly.

^Thats a pretty good deal really. Ray’s good, but IIRC years ago the kit from him ran about $50. And he only has the plastic neck. Probably a better O ring too. Mine’s been issue free but I may have to pick one of these up.

https://i1126.photobucket.com/albums...e002Medium.jpg

I see stuff like this all the time.

https://cimg7.ibsrv.net/gimg/www.rx7...f435171bcc.jpg

^^ew :tear::facepalm3:

Ok ok, no more scary pictures. I buckled under your high-pressure sales tactics and bought one. ;)

Nice product banzai! I deleted my AST when I installed my V mount a few years back and was sad that the only option for the filler neck was plastic. A lot of us will appreciate an actual metal neck with a metal nipple.

Matt