TitaniumTT

How imperative is it to make the AST the absolute highest point in the cooling system? I would think not very becuse iirc the coolant flowing through the TB was higher? Here's what I got - a neat little project in an FC but using the FD waterpump housing because it was ALOT easier. I want to retain the AST idea just becuase I think the whole seperate expension tank/recovery tank is a very good way to go, however, mounting in at the absolute highest point is proving to be a challenge. Mounting the tank a little forward about an inch or two below the outlet on the T-stat is a cake-walk, but it's an inch or two below.

Thanks guys, Any thoughts or suggestions would be great.

DaveW

It (IMO) is not important to mount it at the highest point. The fill cap vent to the AST IS at the highest point, and THAT's what's important. In fact, having the AST a bit lower would aid having the coolant flow back from the overflow tank, since the vacuum in the cooling system would not have to be as great to enable this flow. This would help prevent pulling air back into the cooling system due to leakage in the AST-to-OF tank line.

TitaniumTT

Excellent. Thank you.

What do you feel would be an appropriate volume for these two tanks? The AST/Expansion tank and the recovery tank. I'm building both myself.

DaveW

I'd think the AST needs to be no larger than the stock unit. The recovery tank probably needs to be no larger than a quart or so, assuming it is designed properly, so that the return never gets uncovered. There isn't that much coolant that actually gets displaced in normal use. Of course, larger gives more safety factor if it isn't checked often, but that depends on your use.

TitaniumTT

I was thinking about a quart for the overflow as well. Do you happen to know the volume of the stock AST? Thanks for sharing theknowledge

-B

DaveW

Just a guess, but's pretty small, no larger than 1 cup or so. The key is making it so that it actually separates out any air and directs it out to the recovery tank before it starts letting coolant out.

TitaniumTT

Really?!?!?! That small huh? Wow, I was planning on making that about a QT too. But I see your point about how it doesn't need alot of volume for it to serve it's purpose.

I have this guy for the AST

& this guy for the recovery tank

that will have a drain from the top down to the ground.

I think what I am going to do is build the AST out of some 2.5" AL pipe that I have so that the bulk of the top is really the cap not allowing really any ait to get trapped. The recovery I'll build out of some 3 or 3.5" pipe, whatever I calculate to get it close to a QT or so, and then join the two into one piece. Just for that extra little bit of aggression towards air bubbles, ALL the tubing is going to be -4AN just becuase all I needed was two silly little fittings. Everything else I had laying around. I'll make the "out" from the AST -10 just for ease of connecting to the heater-core line. I had problems with the FC set-up allowing air back into the system from the RAD cap which is the main reason for going with the -4

A cup really???

slo

iTrader: (1)

You have a second gen right, why use an AST, just use a radiator with a cap on top of it....

If you really want to do something creative get a pressurized overflow tank out of another car. for example a ford taurus has a presurised overlow tank with small air vent lines running to several places on the block. The system is basically self bleeding.

Ottoman

for a mounting idea,

i've seen some japanese track cars do this

they weld a "tab" onto the side of the Cold side intercooler pipe that runs to the TB

and then bolt the aluminum AST's tab to that...

it ends up being offset but hey at least it works

TitaniumTT

I hate all things Ford I thought about raping the tank from my wifes Liberty as it is totall self contained, has a pressure in, a larger hose out, and the recovery tank is there as well. But trying to fit something somewhere that was never meant to fit there can be challenging sometimes to mount it sturdily and it hardly ever looks even halfwy decent.

I also thought about using the cap and nipple from the FC rad, and yes it is an FC but going what I have dubbed 7MIC so the FD waterpump and housing is much more appealing, but then I thought that there must be a reason Mazda would use the AST. In a car that went through such scrutiny to save weight and make it as reliable as possible, they wouldn't use this little plastic tank unless it was necessary (Let the flaming begin )

I like that idea of the tab off the Elbow. Another thought that I just had was to mount it where the intercooler and the Radiator meet. Nice and strong there.

slo

iTrader: (1)

The overlow should come from the radiator. Your trying to fix something thats not broken.

I have an FD water pump and belt system, I would recomend you stick with the 13B-re stuff, it fits MUCH better. Next time I pull the engine apart (when I finaly do rebuild), I am going to try and use the 13B-re stuff, but I have a constraint that you don't... needing an FD Air pump...

TitaniumTT

Well, my rad is a completely sealed unit, there is no pressure cap, custom Griffin unit, although I did ask them to weld on a 1/4" NPT fitting so I could plumb up the expansion tank to that should I want to. I have virtually unlimited options with this whole thing becuase of the interchangability of parts. I thought about the RE WP & housing but the lack of replacement parts, the double t-stat, etc etc, I just decided against it. I'm going to try my damnedest this weekend to finish up all the welding and mounting, hopefully snap a few pics as well to get some criticism of the cooling system and such.

Plus using the FD twins it just made so much more sense to use the FD WP & housing.

slo

iTrader: (1)

Have fun fitting a fan (there is very little clearance).

90% chance the WP (13B-re) is an S5 FC unit (I could confirm for you).

Next, you must run a Efan (13B-rew pump). With an re unit you have the option of runing a manual fan.

Manual fan is much BETTER

I would suggest you weld a cap on your radiator in the S4 style...

TitaniumTT

Intercooler runs parellel with the hood, the rad meets a few inches infront of the WP housing and runs on an angle such that it meets the brace between the two frame rails where the oil-cooler once was. Running dual Mocal 19 Row units FD style. Mech fan, although yes it is better, was never part of the plan. I need to get hopping on it, maybe in a day or two I'll get some pics up.

I'm calling it the 7MIC