The 'E' Type Forum

Hi All,
What do you use to remove the diff filler/level plug. Is there a special square socket or other tool that is best for the job. Does anybody know what size the square is on the plug. Thanks.
It is a series1 4.2OTS
Phil

You need an 5/8" 8 point socket rather than the commonly available 6/12 point. Bugger to get hold of here but available in the US from Craftsman tools. When you get it off some people recommend replacing it with a hex head plug.

Thanks, do you know where I can get the hex head plug?

Try eBay? e.g. http://tinyurl.com/pcnlu76 - check the thread size before ordering. Either a hex head or Allen key type, whichever you prefer. You will need two - one for filler one for drain.

Thanks again. Now the tricky part!!! Do you know what thread the plugs are? and are they both the same thread. If not do you know who might know?

Phil

I just use an adjustable spanner. IMO you will change the diff oil so infrequently that it's not worth changing the plug.

My car was being worked on so I asked them to replace the rear axle oil as part of the works knowing that the filler plug was very tight & hard to access . When I collected the car the guys had done the oil no problem. I asked them how they removed the filler plug ? The answer: they used a socket set extension bar the wrong way around (open square female end tapped with a hammer onto the square male end of the filler plug !!!! hope this helps

Jen

It's a standard pipe thread but I can't recall the size. Here we can get a hex headed one at a hydraulic equipment store. I don't mean a hardware store I mean a specialist in hydraulic supplies.

I remember someone telling me he used a window handle from his House !

Carsten

Where is his house?

Difficult to get at I know. I use a 15mmsocket, knukle joint and short extension and that seems to work



Keith Portsmore

5/8 bsp TAPERED

I believe the plugs are not 5/8 inch BSP Tapered.

Having ordered and just recieved two such plugs after well intentioned, but I believe incorrect advice, these are too small and if the thread is BSPT, I would suggest it is more like 3/4 Inch BSPT.

If anyone can confirm please ?

Regards,

Dave

44DHR wrote:I believe the plugs are not 5/8 inch BSP Tapered.

Having ordered and just recieved two such plugs after well intentioned, but I believe incorrect advice, these are too small and if the thread is BSPT, I would suggest it is more like 3/4 Inch BSPT.

If anyone can confirm please?

I'm not certain what size the diff filler/level plug is but it sounds like you are possibly mixing up British Standard Pipe nomenclature and dimensions.

A 5/8" BSPT plug is over 3/4" diameter and your suggestion of 3/4" BSPT would be over an inch in diameter... 5/8" BSP Tapered sounds about right.

Maybe it's your post that is well-intentioned but wrong?

Hi Pete,

Some well-intentioned photos :-














What I was trying to do was avoid people taking the written word as automatically correct - as I did and ordered items on the basis of that information - when I personally think they are wrong and I am right. My money is still that the plugs are 3/4 inch taper thread rather than 5/8 inch.

Again, if anyone can confirm so we all can have the correct information.

best regards,

Dave

All I could do Dave would be go into a chilly workshop and measure two oily diffs in my Sunday best, using digital calipers and look up tables.

You appear to have everything I do, in cleaner condition and more salubrious surrounding so I'll leave it to you if that's OK? You should have your answer in a minute or two and be able to report back for posterity.

The only extra thing I could bring to the exercise would be thread pitch gauges (like a cross between a feeler gauge and saw blade). A good tape or rule is an adequate substitute at that level of accuracy.

I believe it is a BPTF external male tapered thread. BPTF is an abbreviation for British Pipe Taper Fuel, a conical thread to provide a leak-free seal. It is standard BPT but the thread is adjusted to obtain an interference fit to prevent leakage along the thread. The corresponding internal, female thread is BPSF, which is a straight (non-tapered) thread.

Cone / taper
Comparing the cone (taper) angles on the black plug on the left and the replacement 5/8" BSPT on the right appears to show that they have quite different cone angles. So despite the obvious diameter difference, I fear that a larger diameter version of the BSPT would still not work, due to wrong cone angle.

Pitch
The 5/8" BSPT on the right has a pitch of 0.0714" as does the 3/4" BSPT. The black (original?) plug on the left has a noticably different pitch, from some crude measurements from my PC screen I measure 4 black pitches to equal approx 4.75 BSPT pitches, meaning the black has a pitch of approx 0.0848" So even if a 3/4" BSPT was bought, it would have the incorrect pitch, and wouldn't make one turn before binding.

Thread gauges
I have many sets of thread gauges, as Peter says they're like short saw-tooth combs. Found this App (for Android) which seems to cover the same principle, but "live" on the screen. https://play.google.com/store/apps/deta ... ira.thread

Thank you Heuer and David and now I am a bit clearer.

I am familiar with thread gauges and have a full sets of UNF and UNC taps and dies for use on the car and have some original Moore & Wright Unified thread gauges, but I'm unfamiliar with Pipe threads and Tapered threads.

I can confirm the black plug in the final photo is the standard Jaguar filler and level plug. I can see the difference in two threads in that the original black plug has much sharper tips or "crests" and smaller gaps in the bottom of the thread or "roots" than the new BSPT plug. I have found an interesting article in how the seal is created in NPTF threads, not only the flanks as I expected, but how the roots and crest of the threads are truncated and work both together on the major and minor diameters when finally tightened to crush and produce an interference fit :-

http://greensladeandcompany.com/wp-cont ... Gaging.pdf

I tried a different approach in that the later Jaguar XJS has a finned alloy differential cover and I wondered what filler plug they used in that. On S.N.G. Barratt's website they show a plug with the part number JLM632 and the reference .75"BSP, so the mystery deepens.

The good thing is these BSPT and NPTF plugs are only 2 or 3 pounds to buy, so in the interests of research and try to reach a conclusive result to this thread. I'll order both and see which fits best.

I'll report back !!

regards,

Dave

Take a ?2-?3 punt on a 1" PTF plug.

That gets you darned close to your measured 0,95" internal bore. The pitch of the 1" PTF (at 0.08696" or 11.5 TPI) is also darned close to what the black plug appears to be from some dodgy parallax measurements from the photo (and is certainly better than the BSPT plugs 0.0714" or 14 TPI).