As part of water pump replacement I performed several coolant flush cycles. At the last cycle the petcock was tight while I was closing it and then it got loose. Now it won't tighten up and seal. I went through the threads on this problem but nothing worked (pressing in hard while turning CW). I'm trying to pulling it out using vise grips and leveraging it again the tank and it's not coming out. I don't want to break the tank. If I pull really hard can I break the tank, or will I just break the plug?

Between this and the belt, this is worst car repair experience I've ever had (the front axle u-joints are a close second).

Thanks

 

Those things are the devil... hope you get it in there.

 

the guy that services my 2005 dodge diesel will never use the radiator drain. He always drains the system on my truck by removing the lower radiator hose from the radiator. said the drains are junk and he has had too many of them go bad. some times he has had to pull radiator and have it repaired, not just dodges other brands have the same problem.

guess that info is a bit late now, but in the future just loosen the hose.
will save you some grief.

 

Problem solved. I pried out the plug with a screwdriver (placed screwdriver blade between the rubber washer and the underside of the flange with the molded in wing nut and pried against the tank). No damage done. Then I took the plug apart and applied silicone spray onto the threads, popped it back into the radiator, and all is good.

 

Same thing happened to me. After nearly having a meltdown and pulling the petcock drain out of the radiator I found a bolt of the same threads as the plastic plug. I inserted it in the radiator and it threaded right in.
I was dumbfounded as why the petcock plug wouldn't thread in but I think the petcock plug threads were not reaching the threads in the tank. Using the bolt threaded in I tugged on it and it held fine even with moderate force.
I reinserted the petcock after this and it grabbed the threads and pulled right in and sealed perfectly. FIlled the the radiator and its been fine.
My theory is that there is a captured floating plastic nut inside the radiator which whille monkeying with the OEM plug got pushed back a bit. When I inserted the bolt and pulled outwards it repostioned the nut to where the drain plug could catch the threads.
Dorman propucts make a replacement plug as well if something does destroy your original. I think NAPA carries them but try the bolt trick first.
PS- I think the barbed end is just there to keep the plug from falling out. It drains better with it out.

 

^Yep. I picked a spare at NAPA in case I needed it. But so far I haven't.

MikeyB