spurvo

Running the fans keeps the temp low which keeps the pressure down which keeps the system from expanding which keeps it out of the overflow. Each time you are refilling the coolant, you are overfilling the total volume the system can hold. If you were to top off the overflow tank (all the way full, so that a little was peed out the overfill hole down on the body of the tank right next to the AST (or filler neck line in your case) inlet) and then fill the system at the filler neck, when you got hot enough to start flowing into the overflow (13 psi) you would have the overflow tank overflow, as it's already full. This is fine if there is no vacuum leak in the system. The next time you drove, the volume would be correct to allow for the overflow in the system due to coolant expansion. As I said above, if there is a leak (even one that doesn't spray coolant, such as somewhere in the overflow line), then you will not draw coolant back into the system, only air. Thus the lost coolant, and you refill, and the whole game starts again. This air is what you are hearing on acceleration. It's moving through the heater core.

At the risk of devolving into the AST elimination discussion (please don't) I will mention that the AST's purpose was to allow air to escape from the system during the normal expansion contraction cycle. The air they were trying to get rid of was mostly from slight blowby (ALWAYS there, especially at startup) and from boiling off the 500 to 700 C turbo housings when you are running WOT often. Just my $0.02, which I should probably have just kept to myself. Check your Filler neck to overflow line and make SURE it is airtight.

radkins

I've checked the overflow line and its airtight. I also havent been able to find any exterier leaks(small puddles or traces of coolant) anywhere in the system.

spurvo

Hey Stevey. You're not dumb, I'm just ****! All I'm doing with the baster is to pull coolant up the line FROM the overflow tank TO the AST, so when the system does the expansion/contraction cycle, there is no air in the AST to overflow line. That way, I KNOW I won't be pulling air into the engine when it cools down the first time. The coolant dribble is exactly what I saw. Just zip tie that sucker, should do it! Also, a pressure test WON'T see that AST to overflow leak, as it's after the cap, so to speak. Anyway, very happy to be able to help someone where I can. Don't know a THING about the turbo circuits, so I stay out of those discussions!

Dragonz818

Did the trick and no bubbles. It is common that these motors just use more coolant than most right?

I have seen a ton of posts of people that keep motor oil and coolant in their car at all times.....

Maybe am still getting used to it. I can swear it wasnt like this for the first 5 months that I had it. I probably just wasnt checking as often as I am now......

spurvo

Before I replaced all the hoses (14!), I would lose a little coolant. Have a bottle in the pass compartment for just this purpose. After hoses replaced, no coolant loss. You might have a pinhole leak. This will only leak when the engine is hot and running. It will stop after shutdown, and even allow coolant to be drawn back into the system! Mine was in the upper radiator hose, right at the clamp. There was no puddling, and only the faintest whif of coolant while running. I did notice some light rust-like staining around the upper radiator hose connection point (thermostat housing), but had just figured this was left over from previous fillings. A pressure test on your system with the engine cold will most likley reveal the cause, but a test when hot will be better. Or just replace all the hoses as a pre-emptive strike. You don't even need congressional approval for such an action

Stevey629

Ok, so after I ziptie that line, (with the assumption that its leaking) Should I continue to just add to the AST and Filler Neck? Will this eventually burp the air out through the AST or overflow, and make the system work right? The thing is, that the leak looks like its either right underneath the hose, or around the neck, because the plastic sort of bottlenecks and goes in, and coolant either leaks there or seems to drip and run into that area.

I guess I never really figured out how to really burp all the air out...just fill the neck and ast to chock full when the car is stone cold, put the caps back on, and run it with the heater on. repeat until the level stabilizes. right? I also tried leaving the radiator filler neck off, but as I was saying, it just started to rise, and wanted to overflow, so I shut it off. What to do.

Stevey629

alright. I just went to put a ziptie on that hose, and there is a bunch of coolant spooged on the lip that connects the 2 pc construction of the crap stock ast together. think the ast might have gone bad? I'm gonna try getting new caps tommorow, and if that doesnt seem to solve the problem, then Im assuming replacing the ast and connecting hoses is the best idea.

Stevey629

I feel stupid. I just took the car to mazda, ( I know I know) because I didnt wanna try to take it anywhere far driving it, because it might have had a more serious problem. Turns out that it was just a bad cap. Im not sure which one, but Ill get the car tommorow. They charged 74 bucks to diagnose and pressure test the system to make sure there are no leaks, and there are no blown hoses or seals. I had a feeling it was the cap, just didnt know if it was just the cap or something more. Guess I paid 74 dollars to find out. Oh and I guess I didnt burp the systems air out properly. Isnt that impossible to do with a leaky cap? I dunno, he mocked me and said that this car is difficult to work with as far as getting all that air out. When I brought it in and told him that I was in the process of burping it, it then began to leak, he just said that I didnt do it right. NE ways, do u think it would be a good idea to replace the other cap as well?

paw140

Replace them both while you're at it. It's cheap. Hopefully they diagnosed it correctly. Everytime I've ever gone to a dealship (not with my RX7), they screw up everything. They probably pressure tested it, didn't find any leaks, and concluded that the cap(s) were bad. That guy is an *** for mocking you.

Good luck,

Paul

Stevey629

damn, and damn. Well, I've had two shops pressure test it, and I guess its okay. I ended up replacing both caps, because they said that both were bad. I was just going to tell them to replace both while I was at it, exactly like u are saying paw140. Thx for backin me up with that, that guy was being an ***.