Coolant overflow tank / air separator tank ?
 

So I got a question on the RX8's coolant reservoir / overflow tank and can't find answers so I thought I'd post a new Thread here =D

Is the 8's overflow tank supposed to be the replacement / comparison to the RX7's Air Separator Tank ? Meaning it has 3 inlets / outlets wheres the RX7's have 1 inlet / outlet on the overflow tank BUT have an Air Separator Tank in the coolant system that taps into the small 3rd port on the bottom of the Radiator( on the RX8's the 3rd port in the radiator is on the top and goes to the overflow tank), my question is basically: Does the RX8's overflow tank have an integrated Air Separator Tank / Does it work as an AST (like the RX7's to rid air in the system) as well as the overflow reservoir hence the 3 inlets / outlets? ?

I am debating what radiator and overflow reservoir, Air Separator Tank to run in my ride when I put the FD engine in there ( =D ) Since I already have RX8 radiator mounts and reservoir but do not want to compromise the specific engine's coolant variables.. Flipping the 8's Radiator upside down will put that 3rd port on the bottom just like the 7's (other than the nipple being fairly thicker from what I can see in pics) if I am to get a 7's Air Separator Tank to use in line.. I would need to bend the brackets some to make that work OR go all out and get an aluminum RX7 radiator which will require new bracket tabs to be welded, etc.. My main inquiry is to try and understand the differences in the 8's and the 7's (FD) coolant reservoirs, features and flow..

...

Yes that's a nice diagram of the 8's Overflow Reservoir tank I am familiar with the hose routing.. Didn't answer my ? ? tho lol :boink:

the stock Rx8 plastic tank does act like the AST found in FD. but it's more like a reservoir for extra bit of coolant than AST.

but both suffered the same fate tho ---- it's freaking plastic and it WILL break, around the same area too (near the cap)

Thanks for the Swift reply. :icon_tup:
That's what everyone says the plastic brakes so they make these that won't break, so in theory the AST is a better gadget to have in the cooling system, I guess they assumed the Renesis would not need it ? I should definitely get the aluminum AST then and not try and use the 8's reservoir but the radiator I might be able to get away with flipped upside down lol I still have the stocker 8 rad, it's worth a try. While we're in the topic of coolant, will blocking off the two nipples to the throttle body coolant line improve over all coolant flow or restrict it ?

http://rx7.com/store/rx7/images/airs...tank_large.jpg

Rotary Performance | FD Engine Accessories

And here is an aluminum overflow reservoir on ebay I would like to try in replacement to stock plastic ones.

http://i.ebayimg.com/t/GSP-S13-240SX...REg~~60_12.JPG

I know they make metal AST for FD. only problem with it for FE is that there is no way to tell if you still have extra coolant ... you can't see it thru metal, u gotta open the cap with a flash light to check.

Well I mean, the plastic tank sucks but it does last longer than AST from FD (some got away with over 100K miles)

the Rx8 tank seems to bleed the air out much better than the FD's system.

they are different designs though, the FD's system is meant to to take air out, but it still uses a normal overflow

the Rx8 system has the tank/bottle doing both.

in CA where we don't get freezes the plastic tanks outlast the metal ones, the metal ones die from corrosion and or poor quality, sometimes right out of the box.

Well I just learned from reading on and on that some FD guys eliminate the AST all together and get an 86 RX7's filler neck cap with a nipple on it and plug the 2 remaining lines, one from the lower radiator and the one from the AST.. Soo in the name of simplicity THAT is what I will do afterall. And yes people are saying the aftermarket ones are craply made..


http://www.rx7.org/Robinette/coolant_tank.htm

that works too.

Simple is better, always.

It's better, but still gotta point the nose up while bleeding air tho. otherwise, it's gonna get trap somewhere @ the Coolant lines around the throttle body and top of the housing.

WRT the throttle body coolant lines. I think you want to bypass the throttle body, but still run the lines. I seem to remember reading that the extra flow out of the back of the engine helps, especially if the orifice is in the heater core line. I just do not remember where I read it.

I will prolly be capping off the port on the back of the header side of the engine and the one on the water neck and bypass the throttle body line altogether, in the STARX8 I just had a line going from the back, under the plastic intake runners to the water neck, now I would like to just cap them both off, which I would like to think will push the flow harder in the main passage.. I don't even have a heater core. :)

Now you are into the hot side vs. cold side temp balance, and out of my league..

Where in Orlando, I live in Oviedo..

Yeah I dunno about that line, I might leave it just in case since I don't know exactly what it will do to the system.. :wink2:
I live in Dr. Phillips area..

Okay everyone, I have done my share of searching and decided to "revive" this thread instead of creating a new one and cluttering the forum more. If you think it would be more beneficial to make a new thread for my question(s), I will.

My coolant bottle cracked in the typical spot, at the neck where the cap tightens down. I honestly would much rather go for an aluminum tank that wont crack at the neck, than to get a $130 bottle that is going to do the same thing again. Don't need anything fancy, just a SINGLE functional aluminum tank. If I must start with a base tank without fittings and both add all the proper brass fittings, and get an aluminum radiator neck welded on I will. I'm simply asking if someone with proper knowledge would kindly help me complete this project. I will be writing a full DIY on the project as well.

Thanks,
Xero