seems like air is getting into the system causing it to over heat after running a while. I could drive 100 miles before it happens. Tell me what you think.

 

ast leaking????

any coolant leaks???

thermostat stuck closed??

be more specific bro

 

it could be many things. My problem was a blown coolant seal. The car would build pressure real quick and it would burn coolant during cold starts.

 

No leaks that I can see. Took out the thermostat. Hope it's not a coolant seal

 

I had the same problem a while back, all caused by a bad radiator cap (on the AST).
Make sure you change it with another 13psi one, local auto store should have it, good luck.

 

Thanks for the info I will let you know what happen.

 

what color is your AST? is it the stock one? if it is, make sure that it's black, i've read that they turn green just before they crack. If you have an aluminum AST, try (i think it's called) the champaign test. don't know how to perform it, but do a search and you should find a ton of walk through's here.

 

shouldn't he (if he can) change it out for a higher pressure cap? if the stock one is 13psi, that's roughly .9 bar, so why not put on a 1 or 1.2 bar cap to increase the coolant's boiling point, thus making it harder for the coolant to boil and create air bubbles (hot spots) in the coolant lines, and possibly causing a coolant seal failure? or can you not use anything with more than 13psi of pressure with the stock AST?

 

There was a Mazda recall that (among other things) lowered the cap pressure to 13 psi to keep the coolant seals, hoses, etc. from having problems.

 

Exactly, I used a 16 psi cap for few days and kept on loosing coolant after a while, switched back to a new stock one and no more problemos, so far.

 

had the same issues before i replaced my stock ast with an aluminum one.Now verything is gravy.No more coolant bleeding out of the overflow tank.Hope that helps.Odds are it was the ast itself as it was green and the seams along the sides seemed to be spreading apart ever so slightly.

 

put back that thermostat or at least the housing! coolant goes thru the radiator too quickly and does not loose enough heat hence you are overheating.

 

It was doing that before I took out the thermostat

 

install new mazda t-stat
pressure test system, warm
check hose to exp tank for vac leak
search 3rd gen for overheating and burp