Do you need a new one of these?
Radiator Fill Plug - 1987-1995 | Land Rover Engine Parts at RoverParts.com
If so go to the hardware store and buy a 1/2" brass pipe plug for $1.19.
Put thread tape on the threads and screw it in and snug it up.

Here is the one for The Donor, broken, snapped off inside the radiator.



Here is the brass plug.



Here it is installed.



Including the time it took to drive to the hardware store it took me 15 min to replace the broken radiator plug.
I recommend taking your old plug with you to make sure you get a match on the threads.

 

good to know, I had to do that to mine ..... to any one who hasn't broken theirs yet ....you probably will someday...so get the pipe plug now and have it before you are stranded somewhere.

 

That is really good to know thank you for the tip!

 

I don't know that it's a good "tech tip" to tell people to bugger up the threads in the radiator, which this does.
The radiator threads are 1/2 BSPP which aren't at all the same as NPT threads.

 

Tom, I checked the threads before I put in a brass plug and it was as close to an exact fit as my eyes could determine. The NPT may be tapered vs the straight BSPP, but as far as I can tell, that is the only difference. Yes, we run the risk of splitting the female threads on the radiator if we use too much torque, but a little common sense goes far in this case.

 

Well, I think it's important for people to know it's not the correct plug, then they can make their own choice. From the topic it makes it sound like it's a correct fit.
Also, the correct plug is only $4 from Rovafarm, so for another $2 you can not screw up the threads.

 

I agree. 1/2 NPT is not correct and it will foul the brass threads, especially if you use a brass or steel plug instead of a plastic one. And plumbing tape is lame.

Before I knew it was 1/2 BSPP, I took my broken plastic plug to the auto store and the hardware store. I looked at NPT and metric plugs and they most definitely did not match threads. You can plug it with those -- heck you can plug it if you smash a railroad spike in there, but it's going to mess up a real expensive brass radiator. I paid $2.30 for the real thing from Rovers North. You need an o-ring too. They sell that for $1.95 but it's a common size.

 

I wasn't talking about the crappy plastic ones. Though I'd use one of those before using an NPT plug.

 

Man, Spike tries to help you dudes out and you jump all over him. ;^) Nice photos anyway !

 

For those who are curious:

NPT threads have a 60° included angle and follow a Sellers thread form (flattened peaks and valleys)

BSP threads have a 55° included angle and follow a Whitworth thread form (rounded peaks and valleys)

NPT has a taper of 1/16" per inch and is self sealing

BSP is not tapered and requires a bonded washer or other separate sealing element

And I'll just throw this out there -

All the country fried, half assed lame stuff that gets posted on this board and you are silent

A well respected and helpful poster/moderator puts one up that's just a touch low and outside and you guys stir up like trolls under a bridge

just sayin