Can't get radiator drain plug back in

I pulled the drain plug or petcock valve out of the radiator in my 2007 Charger so that it would drain faster. I can’t seem to get the threads to catch when I try screwing it back in. There’s no obvious damage. They feel like they are starting to catch and then it just comes loose again. Not like it’s stripped, just like I’m not doing something right but I guess it’s possible that it’s stripped.
Anyways, any tips or help would be greatly appreciated.

If it’s like on my Chrysler minivans, it is a bayonet mount, not one that screws in. I smeared a little Sil-Glyde around its o-ring. It took a hard push in and a firm twist to secure it.

I’m pretty sure it’s suppose to twist in a little, I just can’t seem to get it in, I spent too long on it. I’m going to try again tomorrow, maybe I’m just tired but was hoping to get some tips on here and you just gave me one. Thank you. I don’t have any Sil-glyde. I think I have some silicone spray (aerosol lubricant) if that’s the same thing.

Vaseline will be OK and more effective than liquid silicone. Looks like it needs a good push and clockwise twist.

PS - Great photo.

Thank you. I kept giving it a good push and twist over and over again. Not sure I had it perfectly straight though. I couldn’t see what I was doing but I could feel everything. Tomorrow I’ll try again and may try some Vaseline.
Thanks, I tried to upload 2 pictures at once but since I’m a new member it would only let me upload one at a time. I figure that one is good enough to see the twist so I don’t worry about uploading another one.

You can buy a new plug for less than $10, and plumber’s grease for another buck or so.
That’d be my suggestion. That would eliminate damaged plastic on the plug as a possible contributor to the problem.
NOTE: get the right one for your car at any parts store… or order from the internet.

Good idea, thanks!

Next time just pull the bottom radiator hose. That drains it very fast.

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That’s what I do.

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Not comfortable with the idea of using petroleum jelly, I’m not an expert but think it might chemically attack the o-ring.

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Yeah just use faucet grease on that O ring. Everyone should have a tube around anyway. I don’t know how it goes in but by looking at it, with the O ring, how can it screw in? There are no threads. So seems to me when you are turning it, its just rotating inside the O ring and not doing anything. Maybe it does need to twist once you get it pushed in, I don’t know, but need to take a good look at it to see for sure. Might be the drain needs to be open, closed, or out or something. But there are no threads.

Look at the tip, it looks like an auger, there is less than 1/2 of a rotation to remove or install this petcock.

These petcocks get stuck when removing them, if you don’t pull it out while turning there is a risk of breaking off the two pins in the radiator. That might be why the petcock won’t stay in now.

Thanks everybody. It does have half a rotation. I don’t know that “thread” is the right word but not sure how else to describe it. I finally got it back in, no Vaseline or lube of any kind used.
One problem was I didn’t have the car jacked up high enough to really get under there. I examined the hole with video and flash turned on and then was able to put a little more muscle into it since I was able to get under there better and get my arm at a different angle. This project has been a real pain. Not finished yet but I’m thinking now that I got through that once, the rest should be much easier.

Good goin’! I recall it takes a lot more force to pull and to install than I anticipated, but no harm done despite the force used. I held the tab with a vice grips.

I once had a slight leak and it was the o-ring being broken. That’s when I first used Sil-Glyde in this situation, to keep the o-ring from getting mangled when pushing and rotating the plug.

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A little antifreeze on the O ring will help lube it too. At any rate, being an elder, I was going to change the coolant in my car and the hoses and thermostat. Managed to put it off for a while while I studied access and the contortions necessary. Then I just took it to a shop. I don’t remember what the bill was but it wasn’t that much.

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Don’t let this get overly frustrating, so much that you damage the radiator or something worse, like knocking your noggin on the engine cross-member. Removing the radiator and fixing the problem on a well lighted work bench may be the best method. Concur w/advice above to use silicone grease (plumbers grease) rather than other lubricants for this problem.

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OP says they managed to put the part back where it belongs.

Plumber’s grease, eh . . . ?!


Yeah well, my first exposure was I went down to the local plumber’s (husband of class mate) to get a new sprayer diverter valve for my kitchen faucet. He looked at it and stuck his finger in a container of plumber’s grease and greased the washer and gave it back no charge. Worked great so next trip to the hardware store I bought a tube and have been using it ever since. One tube is about a lifetime supply so I’ve got about 50 years left.

Back to cars-I drove down and back.

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