Hello folks..I honestly think I have been giving myself way to much credit in thinking I am a decent mechanic but this radiator drain plug is giving me hell and It does not make sense to me...ugh I cannot plug a damn hole I guess....So here is the deal.....Previous owner said the radiator has been replaced with a super dooper one. (yeah ok)....and it originally had a plastic threaded plug in it..I unscrewed it and performed my complete flushing of the system.. go to screw it back in and towards the bottoming of the the plug it wants to kick crooked on me and wont seal flat...Hope that makes sense I am not a word smith...So I say ok fine and run to the AutoZone and buy a actual brass petcock..Throw some Teflon on it crank it in seems legit right? NOOPEE!! Still leaking!!!!!! Identical to the plastic plug!! I totally confirmed its the petcock too..I see fluid seeping out of the bottom of the threads..So NOW I am livid!!!! Have to pull it out AGAIN!! lose half a gallon more on the floor!!!!!!.. How can unpressurized fluid get past a half inch of teflon threads????What in theeee world!! So my last ditch effort was to put a washer and O ring that fit perfectly on the petcock and crank it in tight but not tooo tight almost hand tight...And guess what!????!!! YEP!!!!! STILL LEAKING!!!!!... How could me unscrewing a hand tight plastic drain plug get me in this mess?? The petcock threads are 1/4 NPT

[This message has been edited by jaydaug2008 (edited 08-20-2022).]

Since we don't know what kind of radiator it is, this is from another thread where someone had the same issue. The square body insert was cracked on his car causing leaks.

quote Originally posted by Pegasus88GT: Well I found the culprit. The leak was indeed coming from the drain plug. Funny how things break a few weeks after the radiator's 2 year warranty. The drain plug is two pieces and the clip that the plug screws into was cracked causing the plug to be unable to thread in and tighten. Unfortunately, the clip is a very odd plus (+) shape and none of the parts stores had anything that would work. On the bright side I was able to contact the radiator manufacturer, Spectra Premium, and they are sending a replacement drain plug to my house for free. If all goes well I'll head back home next weekend and install the new plug and put the radiator back in. Gotta love plastic parts!!!

Yes my bad it is an aluminum radiator with the threads 1/4 NPT no matter what I cannot stop it from leaking...thank you for commenting

Was there originally an o-ring on the plastic one or did it just screw in to the radiator bare? The reason I ask is because some plugs have an o ring that makes the seal

[This message has been edited by IMSA GT (edited 08-21-2022).]

Next time keep your hands off the rad drain plug.

Most radiator "water" will drain by right side pipe drain port and a hell of a lot easier to drain w/o a huge mess.

I never mess w/ this on Fiero and many others w/ plastic valves even when I flush a system or replace the rad itself.

After flushing follow directions in my Cave, Coolant Fill

------------------
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 had to replace the radiator on my 87. It didn't come with a drain plug. So, I retrieved the petcock from the old one and it wouldn't screw into the new radiator. I found that there was an insert that snapped into the radiator, then the petcock screwed into that. Look at your original petcock. That big rubber washer is the actual seal. The small piece that snapped out is just the retainer for the petcock. It has the threads, but isn't capable of sealing. The rubber washer seats against a shoulder inside the petcock port. I was lucky that the radiator shop where I bought the radiator still had my old radiator in the scrap bin so I could get the snap-in piece.

So, the radiator you have doesn't use the OEM style petcock? The only radiators I know of that come with the original style petcock are from AutoZone.