I installed a Champion 3 row radiator on my Fiero three years ago and it cools well. The OEM radiator had a chrome radiator cap tthat I removed and tried to use on the Champion. It went on but did not seal.
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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 11-28-2018).]

Thanks for the great info Dennis. I have planned on purchasing a three row Champion radiator and this info will help when I pull the trigger.

Seems odd to me. I have a 3-core Champion Radiator and use standard 18-psi radiator cap used on Camaros with no problems. The parts numbers you listed seem to have too small an inner seal, at least they appear that way from the pictures; they look like the ones on my Honda.

So, have you actually tried a used one before you bought the new one from Ebay, or will the new one be your first try? I am curious to see your results.

make sure any rad cap is Non-Vented for Fiero.
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

quote Originally posted by cyrus88: Seems odd to me. I have a 3-core Champion Radiator and use standard 18-psi radiator cap used on Camaros with no problems. The parts numbers you listed seem to have too small an inner seal, at least they appear that way from the pictures; they look like the ones on my Honda. So, have you actually tried a used one before you bought the new one from Ebay, or will the new one be your first try? I am curious to see your results.

The part number came from Champions listed number for the cap. The Fiero cap leaked like crazy so we will check when the cap comes in. GM did use that cap on some vehicles so we shall see.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

NOT SOLVED. Got cap today.I tried but wrong cap so ignore this post. Wrong part cross reference. My bad!

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 11-30-2018).]

When you say wrong cap, do you mean the vendor sent you a different cap than you ordered, or that the cap you ordered does not fit the radiator?