Ian Vincent Posted July 14, 2010 Report Share Posted July 14, 2010 I am having difficulty finding a sump plug for my TR3a. The original sump was fitted with the usual taper threaded boss and had a sump plug to which a large nut had been welded - great - easy to remove etc. Unfortunately that sump had had a hard life and had been braze repaired in at least two places and was showing signs of cracking where it had previously split. No problem, I acquired a s/h steel sump in pretty much immaculate condition, gave it a coat of paint and fitted it - the only problem was that when I came to transfer the sump plug (the new s/h sump didn't come with a plug), it wasn't a taper threaded hole, it was parallel threaded. No problem I thought, I bought a new shouldered (and parallel threaded) sump plug from Moss but the the only problem is that it doesn't fit. Whilst it has the same thread pitch it seems to be based upon the mean diameter of the taper threaded item whereas the hole in my s/h replacement sump is only as big as the minimum diameter on the taper threaded plug. I seem to remember reading somewhere that there were both taper and square threads used for TR sumps but I can't remember where I read it. Anyway, does anyone out there know where I can obtain a suitable sump plug. As a last resort, I can probably get hold of a suitable tap and open out the thread to accept the shouldered parallel thread plug that I bought but with the sump fitted to the engine which is now back in the car, I run the risk of getting swarf in the sump and I don't really want to remove the sump again. Rgds Ian Quote Link to post Share on other sites
Bob Smith Posted July 14, 2010 Report Share Posted July 14, 2010 Ian, I think that I have a spare sump plug of the type you require, will check and come back to you when i am sure. Quote Link to post Share on other sites
Steve R Posted July 14, 2010 Report Share Posted July 14, 2010 Ian I think the thread is BSP, I bought a plug from a plumbers supplies, use ptfe tape as it seals the thread and also makes it easy to undo. A bit left field perhaps, but its easier to find plumbers merchants in a hurry than TR specialists. Steve Quote Link to post Share on other sites
Bob Smith Posted July 16, 2010 Report Share Posted July 16, 2010 Ian, Sorry can't help with your problem - have sent you a PM with full explanation Quote Link to post Share on other sites
Ian Vincent Posted July 16, 2010 Author Report Share Posted July 16, 2010 Many thanks for the replies, problem solved - I think. It seems that whilst the taper plug is 3/8" BSP the parallel thread plug is 5/8" UNF, although the parallel thread plug that Moss sell is 3/8" BSP parallel. The 3/8 BSPP is 16.66mm OD, the 5/8 UNF is 15.875mm OD hence the former won't fit. Oh the joys of imperial thread forms! Rgds Ian Quote Link to post Share on other sites
qim Posted October 7, 2016 Report Share Posted October 7, 2016 What happens if you try to fit a taper plug into a parallel thread boss (is boss the hole in the sump...?) I fitted a large yellow plug into the sump and it is leaking. I am now afraid I may have damaged the thread in the boss... Quote Link to post Share on other sites
Lebro Posted October 7, 2016 Report Share Posted October 7, 2016 I doubt if you have damaged it, unless the TPI was different (threads per inch) but it would not seal well. parallel holes would normally take a plug with a flange & a sealing washer under that flange. A Tapered hole would need a tapered plug which would not have any flange, but would need either PTFE tape wrapped around the thread, or some other form of sealant. Bob Quote Link to post Share on other sites
qim Posted October 7, 2016 Report Share Posted October 7, 2016 (edited) My car is TS 55938 (1959 Tr3A) And this is the plug that I fitted perhaps wrongly. Tapered, magnetc. Could I have some advice, please? Thank you Edited October 7, 2016 by qim Quote Link to post Share on other sites
RogerH Posted October 7, 2016 Report Share Posted October 7, 2016 Hi Qim, either 33 or 35 from here http://www.moss-europe.co.uk/shop-by-model/triumph/tr2-4a/engine/engines-components/external-engine-components.html You appear to have a magnetic version of the hexhead item. Roger Quote Link to post Share on other sites
Dave Larnder Posted October 7, 2016 Report Share Posted October 7, 2016 Ian I think the thread is BSP, I bought a plug from a plumbers supplies, use ptfe tape as it seals the thread and also makes it easy to undo. A bit left field perhaps, but its easier to find plumbers merchants in a hurry than TR specialists. Steve Steve +1 that is what I did as the original square head had been severely rounded by the p.o. No trouble with it, as a matter of fact, I am about to do an oil change after coming back from Switzerland. BTW It is a steel plug not a brass one. Dave Quote Link to post Share on other sites
qim Posted October 7, 2016 Report Share Posted October 7, 2016 Hi Qim, either 33 or 35 from here http://www.moss-europe.co.uk/shop-by-model/triumph/tr2-4a/engine/engines-components/external-engine-components.html You appear to have a magnetic version of the hexhead item. Roger Hi Roger Thanks, but do you think that having fitted, maybe wrongly the tapered plug I may have damaged the thread in the hole, if it should have been the parallel one? My car is TS 55938 and I understand that the plug with the washer (#33,#34 in Moss) is for earlier cars. Is that so? The tapered plug that I fitted does not go anywhere near the end. Mos of it is sticking out. Is this right? Quote Link to post Share on other sites
RobH Posted October 7, 2016 Report Share Posted October 7, 2016 Unless you have overtightened it trying to make a seal you will probably not have damaged the thread. Since the taper plug does not fit your sump you obviously need the straight one; whether it is for earlier cars is immaterial - perhaps you have an 'early' sump on a later car. No it should not stick out much - that is happening becase it is the wrong plug and only the first bit of the taper fits the hole. Ian's post 5 above means you might need a UNF plug if yours is the same, rather than the one Moss supply. Quote Link to post Share on other sites
qim Posted October 7, 2016 Report Share Posted October 7, 2016 Ian's post 5 above means you might need a UNF plug if yours is the same, rather than the one Moss supply. Sorry... what is a UNF plug? Quote Link to post Share on other sites
RobH Posted October 7, 2016 Report Share Posted October 7, 2016 (edited) If you read Ian's post it will be clear. BSP is British Standard Pipe thread. UNF is Unified Fine thread. Edited October 7, 2016 by RobH Quote Link to post Share on other sites
billy l Posted October 8, 2016 Report Share Posted October 8, 2016 (edited) Hi Ian, the plugs that Moss supply don't fit but the one's from revington do, I put a post on here about this problem a couple of months back.(search for sump plug thread diameter) Interestingly the sump plug is the same plug as fitted to the petrol tank for draining. Cheers, Bill. Edited October 8, 2016 by billy l Quote Link to post Share on other sites
Ian Vincent Posted October 8, 2016 Author Report Share Posted October 8, 2016 Hi Billy, I solved my problem a while ago by recutting the thread on a brass plug that I bought from a plumbers' merchant but thanks anyway. Rgds Ian Quote Link to post Share on other sites
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