First, I well-understand and accept the consensus that Fieros should run NON-vented 16lbs caps on the radiator.

Nevertheless, for giggles this am I decided to look closely at my radiator cap and discovered the word "VENTED" stamped into it. Huh? This car runs cool and never drains coolant into the overflow tank or onto the floor when parked and left overnight. Still, as the radiator cap in a Fiero is not the highest point in the cooling system, gravity should cause fluid to leak past the vented cap and into the overflow tank. How is this not happening in my car?

BTW I've got a 4.9 in it, but that shouldn't matter.

Thanks.

Ernie

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'87 Fiero 4.9 5-speed

[This message has been edited by Warlordsix (edited 10-15-2020).]

Sometimes you get lucky and WP etc holds vacuum so Rad Cap won't leak, more so w/ car parked "nose down" a hill.
Sometimes WP etc only leaks a little air into the system so you don't see coolant "on the floor" because OF Tank hold the coolant.
See my Cave, Radiator Caps

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

I've got a 4.9, but unlike you, I was having trouble with the coolant running out from the front cap. (I had the correct cap. Probably had to do with the grit in the sealant tabs that GM recommends for the 4.9.)
Anyway, I put a 20 lb non-vented cap (no little disk in the middle, either) and added a fill adapter at the rear. I placed a coolant bottle where the stock air filter canister used to be, and put the regular 15-16 lb cap on the fill adapter. I haven't lost any coolant since then.

[This message has been edited by Raydar (edited 10-16-2020).]

Makes sense, Ogre, and that's a clever solution, Raydar.

Ernie

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'87 Fiero 4.9 5-speed