What PSI cap is supposed to be stock on the filler neck? The repair manual refers to the AST cap as the radiator cap. So is the filler neck cap supposed to be "no" pressure and the AST cap 14-16lbs or visa-versa?

Does anyone have orginal OEM caps? ...if so, what PSI are they? Could too much pressure burst the coolant lines?

 

I have a 16psi filler neck cap got it from autozone...works like a charm (can't go wrong for 2 bucks)

 

its suppose to be 13psi (the 16psi one is the wrong one dude!!!)

 

Which one is supposed to be 13psi? ...there are two.
Are both of them supposed to be the same?

My friends AST cap is .9bar (13psi) but he also has a .9bat filler neck cap. Is the filler neck cap supposed to be 0 psi?

Oh my Blitz is 18.5psi, which I was running before the overheating issues.

 

yep both. seach for more answers.

try going to http://www.robrobinette.com/ or http://www.scuderiaciriani.com/rx7/ for more in depth explantion

 

^ neither of those mention the PSI of either cap, nor does the manual.

 

My stock oem filler neck cap is 0.9 bar (13 psi).

 

i think thats because it already had the recalls done on it, all fd's i have seen had the .9bar neck caps as well.

 

no one has really addressed the original question: will the use of a 16 psi cap (as opposed to a 13 psi) create too much pressure? could the lines burst if it got up to temp? I have the pettit ast which came with a 13psi cap, but it went bad and I replaced it with a 16psi due to availability.

 

More pressure in your coolant system will, of course, increase the chance of a burst hose. The car (93 at least) originally came with a 1.3 bar cap. Part of the coolant recall put a lower pressure cap on the car for the very reason that you mention; burst hoses.

Mazda claimed the burst coolant hoses were causing engine fires.

A higher pressure cap will allow higher coolant temperatures before the coolant boils, which is a good thing. As with everything, there are trade offs.

My car has a 0.9 bar cap on the AST, and the coolant filler neck cap is not marked. I will be replacing all my coolant hoses soon, at which point I will go back to the 1.3 bar cap.

Please see:
http://www.scuderiaciriani.com/rx7/cooling.html#CAP
for more information.

If you need a 0.9 cap, go to Mazda. If you want higher, look here:
http://66.216.67.51/subcatmfgprod.asp?0=352&1=355&2=-1

 

nice sig ryan; but now you have to adjust that hp rating

 

After looking at the coolant system diagram, the filler neck and the AST, I realized I wanted I higher pressure cap on the filler neck because I do "not" want it releasing coolant there but instead I want it to flow in the the AST. The hole to the AST in the filler neck is lower then the bottom of the cap anyhow, so it makes no sense for a lower pressure cap there. So I put back my 1.3bar/18.5lbs Blitz cap on the filler neck.

I do want the water and air to escape from the AST to the overflow, so I removed the rubber stopper from a .9bar cap and used that on the AST. I'm not sure if that makes it a zero pressure cap or just lowers the pressure. So far it has worked excellent. The AST purculated like a hot coffe pot and no noise from the UIM or other places. The filler neck stayed full and the AST was mostly full. Oh and I recomend the Alumaseal over the CRC block weld.

 

Why? I think I'm going to try one or the other and would like the pros and cons of each. BTW, what's the best method of adding Alumaseal? Will I need to completely flush/degrease my cooling system like the "O-Ring Fix" that's been posted on numerous occasions?

Thanks!

 

oem mazda setup with ast:

ast gets a st'd pressure rated cap. was 1.3bar, now .9 bar (avoid splitting heat weakened coolant hoses to turbos). I use 1.1 bar stant. Should change every couple years ... they eventually leak pressure internally.

mazda oem filler neck cap is a non-relief cap ( no internal spring and lower sealing disc ), and thus has no pressure relief rating markings. Any cap should work there.

 

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What he said...

I prefer the original 1.3 cap, as the coolant boiling temp is higher. Just keep an eye on (or change) the hoses as part of your maintenance.

 

I concur. You only need a pressure cap if there is a vent hose coming off the neck you put it on. If you have a stock of aftermarket AST, you should have a pressure cap on there, and a simple (no spring) filler cap on the filler neck. A pressure cap will work on the filler neck, too, but its pressure rating is completely irrelevant. If you have removed the AST, you probably have a vent tube coming from the filler neck, so you need a pressure cap there.

-Max

 

What's the correct cap for those of us who have eliminated the AST? Steve's site says you should be using a 16psi cap that has a spring. Is it okay with the 0.9 bar cap that comes with the replacement filler neck (AST elimination)? (*still grumbling about the split hoses from the AST*)

 

The 0.9 cap that comes with the replacement filler neck is fine. If you are boiling the coolant too much and want to try a higher pressure cap (higher pressure = higher boiling point), that is fine, too.

-Max

 

Kewl. I've noticed the coolant level dips lower in the filler neck with the 0.9 bar cap. I figured it had to be from the lower pressure cap allowing more evaporation losses. Thanks, Max.