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MG MG Y Type - Cylinder block drain tap

Can anyone confirm what the screw thread is on the cylinder block drain tap hole. A friend sheered his tap off trying to stop a leak and in the process of drilling out the remains I think we may have damaged the internal thread. He is ordering a new tap, in the mean time we need to run a tap through to clean up the thread. I suspect it is 3/8 BSP.
Peter
PW VIELVOYE

Having checked the BSP thread chart I see the OD is not the same as the thread size, 3/8inch OD would be 1/8 BSP.
Peter
Peter Vielvoye

I have exactly the same problem - if the threads have gone then a 1/8bsp tap will be of no use - you may have to fit a helicoil with 1/8 bsp internal diameter - let me know how you get on. I am currently using an old aluminium bolt as a temporary measure.
David Mullen

It is the same as an MG TD Drain Tap. Dave DuBois is the man to answer this one so I will drop him a note and ask him to comment.

Paul
Paul Barrow

The thread of the drain tap is, in fact 1/8 BSP. If the threads are ripped out, you will need a Recoil to repair it (to my knowledge, helicoils don't come in British sizes. when I had to repair the threads in the block or our TD, I got a 1/8 BSP Recoil kit from Uni-thread http://www.uni-thread.com/ in England. Cheers - Dave

PS - For a list of all fasteners, plugs and studs used on the XPAG engine, see the chart, XPAG/XPEG Engine Fasteners in the Other Tech Articles section of my web site at: http://homepages.donobi.net/sufuelpumps/ Also, if I remember correctly, Paul has put this chart on the Y type web site.

David DuBois

Thanks Dave - that was great.

Everyone else,
Same lists threads etc. is available on www.mgytypes.org under the Techincal Centre, Technical Data section courtesy of Dave Du Bois.

Regards

Paul
Paul Barrow

Thanks for all the help so far. The replacement tap arrived last week but did not fit as it slid right in the hole. On closer examination of the remains of the extracted thread the OD was slightly greater and the thread was slightly coarser than the new 1/8th BSP on the replacement. On consulting the thread lists refered to the only one it could be is 10mm Fine Metric. Was this the original drain tap. the lever is on the side of the older one and on the top of the new one. On Monday we go in search of 10mm fine metric bolt. The last resort will be to drill and tap for 7/16 BSF or UNF
I suspect the recoil would be a bit tricky with the engine in situe
Peter
Peter Vielvoye

This parallels my experience - I suspect the hole was 1/8 bsp but loss of threads makes the replacement tap just slide in the hole - mine did exactly the same. I have temporarily put in an aluminium bold (soft thread) to block it up.I suspect that a helicoil with an internal diameter of 1/8bsp is the answer. I think to get at the hole with a tap will require the removal of the front wing and inner wing. Buying the brass drain tap is expensive for what it is so its worth bearing in mind that you can find them on ebay at lower prices as they fitted a number of other cars.
David Mullen

Thanks to all. The job is now done. The hole left was cleaned out with a 10mm drill just over the 9.7mm tap drill size for a 7/16th BSF. The BSF tap went in being turned with a spanner and the hole is now sealed with a 7/16th set screw and washer.
David hope this helps with your long term solution.
Peter
Peter Vielvoye

This thread was discussed between 27/02/2009 and 14/03/2009

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