AST removal and Rad caps?
 

I was looking at some pictures of a car earlier running a single turbo setup and I noticed that they appear to have removed the AST from the water system and had a pipe running direct to the water filler bottle down infront of the wheel.
Is this a common setup and if so what are the pro's and con's for it.

Also can you run a traditional style sprung rad cap on a 13B motor on the ally header tank bit attached to the engine or will this not seal properly or just bugger up the way it works?

Thank you
Lee

The Easiest way to remove the AST from the system is to get a Radiator cap/filler assembly from a 86-88n/a FC That will give you a cap assembly that has a nipple to run the overflow hose to the tank. Plug the remaining nipples and you are set. In stock form with the AST the main cap( on the water pump assembly) has a 13 lb cap I believe. The AST is a speacial one from what I remember without a spring pop-off.

I run no AST and have NO issues. Many will argue otherwise. Your choice. Search the 3rd gen technical section for this topic and give a read to a few of the better threads.

Dave

There's a couple of ways of doing it.. In each scenario, you need a FC RX7 neck and you run a hose from neck to the overflow tank. Here are the variations that I've seen:

1. Cap the remaining nipples on the water pump housing and the bottom radiator (like BI7s mentioned - I did this)

or

2. Run a hose from the waterpump housing nipple to the bottom of the radiator nipple (no capping).

Arrh.. I see the filler neck nipple.. Yes I wondered how it would work! Does that mean the system only blows water out if it get's t hot and cannot let it back in when it cools?
Is there a good reason to do this mod? Is it purely for tidyness or is it more efficient cooling and less possible leak points?

Cheers
Lee

I dunno what AST is, as I'm not a 3rd gen guy, but it sounds like you're describing an overflow tank. As long as the top is sealed to the hose, as the coolant cools back down, it will suck the overflow back into circulation.

AST= Air Seperator Tank

Unless you have the S4 rad cap assembly, you do NOT have the overflow nipple. If you are talking about the nipple that is coming out of the Aluminum filler neck housing, that will just push all your coolant out if you run it to the overflow tank. You MUST have the early second gen rad cap assembly to do this mod.

I did this to rid the enginebay of all possible leak points. I notice NO difference in cooling of the car. Street or track;)

Dave