Thread size for radiator drain plug.

Hello RT,

I posed that very same question not so long ago. Unfortunately no one actually knows the thread size, but Al (tvr_v8) did come to the rescue by advising the following...."Can't help you on the thread sorry but they are the same as the plug on a Range Rover/Discovery diff... Would recommend you replace the nylon version with a metal one as they frequently weaken and shred the cap leaving the thread stuck in the radiator/diff according to where they happen to be fitted if you overtighten them by even the slightest.

Any decent LR specialist will keep metal ones in stock for not much $.

http://cgi.ebay.com.au/Land-Rover-Disco ... 2eb06c0e27 for example"

Since then I have found that the Land Rover part number for the brass drain plug is TYB 500120.

I have also obtained a spare OEM P6 brass plug from a friend and fellow Rover owner, but as I don't have a thread checker I cannot identify the thread. I do know that the fittings for the AC mechanical fuel pump will screw in the radiator, and these to my knowledge are national pipe straight threads, but once again no one seems to know the actual size.

Ron.
 
That's a good piece of info!

I'm surprised that nobody [apparently] knows the size of the thread, though! Couldn't somebody measure with a pitch-gauge or similar? :?
 
That's not the same as a P6 rad drain plug, it's the 13/16" AF plug that fits into a radiator header tank or thermostat housing. (Or diff)
P6 ones are (IIRC) 9/16" AF
 
harveyp6 wrote,...
P6 ones are (IIRC) 9/16" AF
Click to expand...

Sorry Harvey, that is not the right size. A 9/16" socket is too small. Same with a spanner, too small. The socket that I do have that will fit is marked 3/8 BS. I do have the correct P6 plug as I indicated above.

What size is the thread though?

Ron.
 
Well the socket that fits the drain plug is a 3/8 Whitworth....(BSW).

I also have a British Standard Pipe Taper (BSPT) plug and it too fits the radiator. The thread form of the two plugs are identical as BSP threads follow the BSW standard.

http://en.wikipedia.org/wiki/British_Standard_Whitworth

http://en.wikipedia.org/wiki/British_st ... ipe_thread

P4230120.jpg


P4230121.jpg


Ron.
 
if it's a 3/8" BSPT tap you have ron, you are probably on the money size wise and you may find that the original plug will have a parallel thread (BSPP) rather than the taper thread you find on BSP plugs as they are tapered so as to tighten and seal as you fit them. So the plug in your pic on the right will have a 3/8" BSPP thread so it seals with the washer on its flange. The engine sump plug is a 1/2" BSPP (parallel thread) thread as i had that size tap through it to clean it up and Rover would use the same thread type (BSPP) for all its other coolant points eg:- the block drain points are 1/4 BSP.
strangely my rad dosent have a drain plug nor does my doner car's rad??
 
Hello Scott,

Appreciate your confirmation on the thread sizes. Yes indeed, the original BSPP seals with the fibre washer whereas the BSPT seals with the threads. Excellent to know about the sump and drain point threads too!

With your radiators, it is almost certain that at some point in the past when they were in for a new core, the drain plugs were removed. Radiators in new cars don't have drain plugs, so in order to empty you need to remove the lower radiator hose, which of course still leaves coolant inside. Whenever I have my radiators recored, I specify to them not to remove the drain plug, as a friend of mine took his Rover radiator some years ago to get a recore and upon collection,...the drain plug had been removed. He was none too pleased I can tell you!

Ron.
 
Well, all things are never the same especially where Rover was concerned... :shock:

The radiator that I fitted yesterday has the brass drain plug as pictured above. The radiator that I removed has a nylon plug which dates from 1974, it being part of the original radiator that was factory fitted at that time. I had a suspicion that it was different size, but better to be sure before speculating. As can be seen from the photo, the sizes are completely different. Looking at the threads in the end tank, I tried a 3/8" NC 16 tap and sure enough it screws in very nicely indeed. Comparing the tap with the nylon plug shows threads which look essentially equivilent, although the nylon threads are pretty tired.

So the drain plug threads in both Rover radiators are completely different.

P5020152.jpg


The way in which the fan shoud attaches is also different between the two. The original one that was factory fitted in 1974 has captive nuts beneath the top plate and bolts are used to secure it, whereas the radiator that I purchased brand new from a Melbourne Rover P6 specialist in 1990 has threaded studs that accept 1/4"UNF nuts, like the one shown in the parts book. Neither radiator came with stays, which I have seen fitted locally to a radiator in a U.K assembled P6B, also as shown in the parts book.

Do you know what sort of plug that you have in your radiator?

Ahhh the mysteries of life,
Ron.
 
Question for Harvey if you don't mind....did the U.K Rovers that you have seen over the years all sport the brass drain plugs or did the nylon type like in my original radiator also surface on occasions?

Ron.
 
Thanks Harvey. Now that is interesting,...

A Ford fitting Dave... :?

Well whatever the reason my OEM radiator was fitted with a nylon plug, one this is for sure,...37 years down the track,..they sure don't make nylon as good as this anymore

Ron.
 
Well the saga on the thread size continues, the one that accepts the brass drain plug. I found my 3/8 BSW tap, and it is not even remotely close to the size...way too small in diameter. So although a 3/8 BSW socket will fit the head, the thread is a totally different matter. It is likely a BSW = BSP thread, but what size, don't know. In actual fact although the 3/8 BSW socket fits, it is if anything a twizzle too big, although that maybe down to the brass edges being a little worn. I filed them flat prior to fitting and found a spanner that fits perfectly,..marked BSA with the number 15 upon it,..looks as old as the hills. I have not a clue what size that is supposed to be.

Anyone got a radiator sitting empty and a selection of taps?

Ron.
 
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