AST install - flush coolant or replace ast and top off?
 

I did search but did not see this covered

My first mod (second really, boost gauge) is a secondhand Petit AST. Question is whether I need to drain all coolant, or just swap the units and top the petit AST off with a similar amount of coolant as I lose from the stocker - and whether I will have to "burp" the lines afterward or just keep an eye on the level for awhile topping off the overflow tank as needed.

If it requires draining I'd almost rather wait a couple months until I purchase a Koyo rad.

thanks!

I dont think it requires draining all the coolant. If your coolant is already fresh and new, id just replace the part and top it off

agreed

Just elevate the lines and you shouldn't loose too much. Fill up the AST and the filler neck with coolant/water when finished.

Take off the throttle body line. That is the highest point. This burps the system rather well. Re attach the line and top off.

Is there coolant in the tb line?
I should really bypass that anyway,butterfly won't freeze up in Virginia

^yeah but it will affect cold start idle. check out the link in the FAQ for detailed info.

if you are upgrading the rad soon, you should be OK to just top it off. Search on other threads about fitment issues before deciding on the Koyo.

Plenty of good threads on the burping / air bubble removal procedures if you search for them also or go to the FAQ thread.

Put the AST on now - the month or two you wait could be when the stock AST fails. It takes maybe 30 minutes to change, and you don't lose much coolant at all.

You really shouldn't have much air in the system either from just doing the AST.

Dale

In deference to Larz, I'd consider unhooking the TB line when your filling the whole system back up after your radiator swap. Otherwise, your just making it more complicated than it has to be. If you simply elevate the the AST lines, I doubt you'll let that much air in the system that it can't purge itself...after all, your installing an Air Separation Tank. ;)
BTW, the TB coolant line is also a good spot for an aftermarket temp gauge if you want to add one later.

Fabulous advice from everyone. Man, I get one of my dream cars and as a bonus it turns out the rx7 forums are the best car board I have ever been on. Tip my cap.

not that anyone will much care with all the modified cars on here, but this is a pic of my baby. My father in law took the shots, he is a good photographer, with nice gear but it was a bad day for it, too sunny. Still, clean car with a fantastic Klasse detail job by my buddy. More pics to come in a showoff thread later

http://lh3.ggpht.com/jameschristy/SK...jpg?imgmax=912

did i miss something? you said pic and i cant see anything?

anyways when i did my ast without draining the coolant you just gotta be fast and make sure u clamp off the lines as you pull em off and make sure you suck most of the coolant out of the ast before you do it. from there on its not to hard gl!

no pic? maybe your browser just isn't loading it? (it's big)