Kahren

iTrader: (13)

i thoguh ast is supposed to separate the air from the coolant thsut makign it not have air pockets, but everyone seems to be talkign about the localazied boiling and how it can ruin teh seals...can someone clarify who has complete knowledge of this

dubbs693

yea it does but it can crack which ruins your car.. replace it or remove it

Kahren

iTrader: (13)

is this the only response i am going to get?

Mahjik

iTrader: (1)

I don't see how the AST boiling would ruin the coolant seals. I've never heard of anyone having a problem with the coolant in the AST heating up. It's going to have the same boiling point as if it's running anywhere else in the engine, the coolant properties aren't going to change.

I'm not sure what you are exactly asking....

Mahjik

iTrader: (1)

Oh, but yes, it's suppose to remove air from the coolant since air in the cooling system is a bad thing. Mazda even uses one on the LeMan 767 car, granted it's raised much more than the FD AST so it probably works MUCH better.

Kahren

iTrader: (13)

i am talking about the localized boiling in the engine where the coolant passages are, and if there are air pockets there then those spots will heat up a lot more then where there is coolant, because of the contact with antizfreze and its capabilities to remove heat from teh engine. the parts that overheat those ares will have damaged pieces of coolant seals thus needing an engine rebuild. If teh AST removes these air pockets then why is it that i see a lot of peopel on this forum talk about this and being afraid of it. if there are as many air pockets with ast as withogh it then what the hell is teh point of it? and how come no other car has it as far as i am concerned.

grampa

Localized boiling is just that, an area where the surface temperature of the coolant passage is so hot the coolant boils.

The AST only removes free air in the coolant. If this free air is a result of localized boiling that did not go back into liquid state it is a little to late to be of much help.

Do searches about Evans coolant and the properties it has to avoid localized boiling.

Kahren

iTrader: (13)

hmm now i have another quastion, that gurgling and bubling that you hear sometimes if you pop your hood and listen carefully, woudl that be coolnt boiling? or is this just coolant moving aroudn because of the pressure?

KevinK2

"If teh AST removes these air pockets then a lot of people on this forum talk about this and being afraid of it."

people are afraid of the weak oem plastic AST failing, as it often does. get an aluminum one.

AST type device is recomended anytime top of rad is low, relative to top of engine. Subaru wrx also has one. The FD ast will not instantly remove air when running, as it only sees a small % of coolant flow (esp oem), and at high pump speeds any entrained air in coolant has just a brief time to rise in the filler neck to get to the ast. Air will rise to filler neck top after shutdown, and will get pushed out thru ast after next cooler start.

Air can also enter system as small hose joint leaks, or even some exh gas at cold start.

With glycol/water mix, some nucleate boilng is normal, but vapor should quickly condense if bulk coolant temp is not excessive like 230F+.

Best to control glycol/water boiling by keeping pressure tite system, replace/test cap often (pressure loss easy thru flimsy central return valve), and cooling fluid better than oem 221F set point (parking lites, miata switch, fan switch mod, seal belly pan leaks, etc).

Audi, vw, gm, mercedes have high mounted ast-ish plastic tank that not only removes any air, but also stabilizes pressure in cooling system near the cap rating, further avoiding excessive boiling (DNB) events. No room for one in FD engine bay.

j9fd3s

iTrader: (3)

there are lots of cars the use an ast. all of the current mazdas use them and the 626 ones fail faster than the fd.

mike

Redevvl

Not to mention the stock AST is plastic and has a tendency to crack over time as it is exposed to engine temps. If that happens there goes your coolant and quite likely you will be looking at buying a new motor. I bypassed my AST to avoid that weak point. Next is a new M2 radiator. The stock radiator has plastic end tanks and is another potential weak point.

Kahren

iTrader: (13)

i already have a fluidyne and the aluminum ast i wass just wondering...

Redevvl

Still not sure of what your question is?? Sounds as if you have done what is recommended already. If you are looking for an answer regarding the purpose of the AST and what it's purpose is, then a search in this forum should help answer your question. Sometimes depending on your intercooler upgrade, you may either have to eliminate the AST or in your case upgrade to the aluminum version.

FD_Pilot

iTrader: (1)

The car is circulating coolant through the engine when the car is running.

When you cut the car off... coolant isn't moving. It starts to heat up...

That's why you hear the "boiling" for 1-2 minutes after the car us shut off...because the coolant is boiling...

If the coolant was boiling WHILE the motor is running... you motor would definately have a quick death.