I have done so much stuff trying to fix the cooling issues on my 1988 2.5 Fiero. I have burped it countless times so I know it is not that. I even recently installed a new head gasket along with a new intake manifold gasket. I changed the radiator cap at some point, along with the thermostat cap as well. Many new thermastats, currently the one in it I even drilled a hole in it to let air pass over easier. I cannot see anyplace where it is leaking. I have very carefully inspected for damaged lines under the car as well. 2 new water pumps, among other things. The car runes fine for like 20 - 30 minutes then bam, gauge pegs. The overfill tank is suddenly full, and I guess air is getting trapped in the motor area. I am losing my mind over this. I guess next step is the radiator, although I am getting tired at throwing money at this.

quote Originally posted by Firezappy: I changed the radiator cap at some point...

Are you absolutely sure it's a non-vented radiator cap that's been installed?

Check out The Ogre's Cave/Powertrain/Cooling/Radiator Caps

I took of the cap and after carefully reading the cave I am like 90% sure I have a vented cap. The little dime piece of metal is loose. So I went ahead and ordered this off amazon.At least I know I had a head issue, because the exhaust got much cleaner after I changed the head gasket, but if this stupid cap was my main problem all this time...Ouch.

Thanks for the pointer, what an annoying book error, I got that cap like 2 years ago at Autozone >.>

Radiator would have been higher up on my list than water pump. If it still overheats with NO thermostat, and the fan definitely works, I'd say radiator.

quote Originally posted by Firezappy: I took of the cap and after carefully reading the cave I am like 90% sure I have a vented cap. The little dime piece of metal is loose. So I went ahead and ordered this off amazon.

I suspect that installing the wrong rad cap has ended up biting a lot of Fiero owners over the years!

If had a vented cap and have overflow tank fill or worse often...
Read cave cap page again.
page give some highlights to look for air leaks.

Air leak sucking can turn to coolant leaks pissing on whatever and more so at 15-16 PSI system pressure when hot.

Most Coolant Pressure testers won't fit Fiero w/o taking hood off.
Is why GM/ACDelco made (made by Stant as ST-255 and sold by others w/ different PN) a tester to fit a small place there. You can find them thru Eflay etc. But most are very old and need work before use.
Others multi fit testers but too big because big "cap" plus "air hose" connector use w/ them.

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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