I have a slow leak on the hose connecting to the top of the AST. I'm not sure if this is the cause, but my overflow remains empty whether or not my car is warm or cold. However, the filler neck & ast remain near the top and I can drive for weeks without my coolant buzzer going off (It hasn't yet).


Is the leak on the top of the AST causing my overflow to stay empty?

 

If you are talking about the hose that takes the overflow FROM the AST to the overflow tank in front of the passenger tire. Then it is possible. Depending on the size of the hole. Ihad one that had a slice in it. Couldn't see the leak until it got really hot. Then it would travel towards the tank but never reach it. Again only when hot. Also if the tank was not filled completely after the last time it was burped, then it may have sucked the remainder of the coolant out of the tank. Hope this may have helped.

 

Well, I don't know if it goes from the AST to the overflow. It's the hose that connects right under the cap. If you are right, then the overflow should have coolant in it when the engine is hot, but it doesnt. Any ideas?

 

Yes, he's talking about THAT one (under the cap )

If there is a leak in this hose, coolant will go out, but not get to the overflow tank, as it's leaking out the hole. Eventually, the coolant level in the engine will reach an equilibrium with the amount of expansion/contraction that goes on, but you WILL be getting air into the system, which can lead to hot spots and failure of things like O-rings. Get the line from the overflow properly sealed. A nice way of testing is to pull the line from the AST (the one under the cap), fill the overflow to the middle of the stick, and put a turkey baster in the end of the line where it attached to the cap. Pull vacuum at the baster, and see if liquid comes up, with no bubbles. Also look for liquid leaking (best to pull the undertray to look for this, as it will often mask the overflow tube leaks and look like another place is leaking. Put the undertray BACK ON, when you are done! ).

 

The overflow/resevoir tank acts as 2 things..1) A catch tank for the coolant system when it overcomes the cap pressures.(Gets too hot) 2) It acts as a supply for the coolant system when there is a demand for more coolant.( When the engine draws coolant back into the system. )When the system is burped after any air enters the system, the resevoir tank should be filled half way to help supply the system while filling. Try filling the tank with some coolant and watch the level for a few days.See what happens.

 

Awsome test spurvo. And better explanation than I.( with the expansion /contraction example)

 

Thanks for the help guys, I'll try filling the tank a little and checking the level, and report back.

 

i hate it when they never report back!!!


To revive this:

I am in same boat. Just received my FD today from the Transport company. Was already inspected by Rotary Performance days before it was picked up, all was good.

Drove it around, etc. Got it home, let it cool:

t-stat neck=full
aluminum AST=1/3rd? full or so.
overflow=empty.

there was some moisture, so not completely dry, but it was defintely not holding coolant.

I did notice some droplets around random things on the bay. didn't smell like fuel or oil----

probably just a leak yes?

mere hours of ownership, and already unanticipated fun!!

 

Check that the overflow tank is not leaking/craked, if not replace the ast cap and hose connecting from ast to overflow tank.