Hi everyone, thanks for all the imput and advice. I thought I’d share an update.
My mate was too busy to come over so he sent one of his senior mechanics. He said he was a gun at tapping threads and had done lots of sump plugs.
As you can see from the photo it wasn’t successful. In addition to the sump plug being on an angle the sump plug is also a loose fit.
He used a M18 tap with a 1.5 mm pitch, which can only be used if the existing sump plug hole is NO GREATER than 16.676 mm. I told his boss (my mate) that my sump plug hole was 16.6 mm prior to him attempting the repair.
I’m not sure why he went for the M18 1.5 mm pitch tap. He may not have had a bigger tap but he knew I had a tap and die set which contained a M20 1.5 mm and M20 2.5 mm tap.
Hindsight is a wonderfull thing, I should have attempted the repair myself. He was very quick , basically in and out of my place in 10 minutes. I would have spent as much time as i wanted on the repair.
I would have used the M20 1.5mm tap but I most likely would also have got the angle incorrect. If he had a problem getting the angle correct with all that tapping experience I can’t see how i would have got it spot on on my first go.
I can’t blame the mechanic who attempted the repair. He was obviously pressed for time.
For the time being I have used a big diameter rubber o ring and tethlon tape. I took it for a long 30 minute drive and it’s not leaking. There were metal filings which I tried to clean out as best as I could.
For the short term I’ll stick with this bogus temporary repair. In the future I’ll have to replace the sump from the one on the spare engine. As you can see from the other photo whoever did that sump plug repair did a good job. They must have had the benefit of repairing the sump using a milling drill and tapping it on a bench. (As Frank suggested)
That is disappointing news. I presume…an over confident mechanic that did not appreciate the potential for error… He likely just thru the tap in and started turning. I think you would have done better.
There is a last ditch method of fixing that before replacing the sump. You would need a cutting mandrel with a pilot bushing that fits snug in the threaded hole…then you would cut a new face square to the threads.
Finding one the correct size might be difficult. I would probably make my own.
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The problem was likely that the hole was already threaded for the helicoil, Nick…
…it is very difficult, and not advisable, to cut new treads, possibly mismatching, into old threads. And doubly difficult when the diameters are near matching - the old thread has a tendency to ‘steer’ the tap. The result is usually a variant of cross threading when the bolt (tap in this case) is forced in at angle - and cuts its own thread across the old thread. And here it is probably two different thread types and pitches…
No consolation offered; the only recommended procedure is to drill out the hole to the next size - clearing out the old threads. A ‘taper’ plug, shown by Rob is then almost self guiding in a clean bore - but maintaining ‘perpendicularity’ both for drilling and tapping, is vital. Particularly when the material, as here is thin.
The ‘loose fit’ of the plug is a danger sign; the ‘cross-threading’ has likely seriously weakened the hold - so later oil changes may cause problems. And the looseness may cause unthreading on the road - with rapid loss of oil…
I think a proper repair is very advisable - it’s not an area for bodging…
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It’s probably the best way to ensure that contaminants and debris is drained out with the oil, David…
It’s not unusual for dealership to take easy paths - negative effects of ‘incomplete’ oil change is a very long time coming. After all; the oil filter is there for a purpose…
Another bodge… a drain valve (correct for the application of course), ideally in new M20 threads if possible, and then just glue it in? It would be in there forever and the threads can’t go bad ever again. Beats pulling the pan.
Or another helicoil/thread-sert/time-sert.
This is what I repaired the sump on my S11 in 2014
Yes it leaves a small amount of old oil in the sump but certainly less than stays in the oil cooler circuit in my old XJ40
The large plug is araldited in situ.
This is what makes me anxious and hesitant to drive the car. If the repair wasn’t bodgey enough it certainly is now. I’ve thoroughly degreased the sump plug and surrounding area and applied this gorilla tape. I’m seriously impressed how good this stuff is.
At least now the car is drivable so i can drive it to a machine shop or workshop and they can drill it out and re tap it to M20 size like you suggested.
He knows about it. He sent me a text enquiring how it went and I showed him the photo of the sump plug on the angle. The sump had been oversized by the previous owner so the mechanic . was behind the 8 ball even before he attempted the repair on it. My mates helped me out plenty of times before, it’s just this time it didn’t work out.
Thanks I’ll print this suggestion out and show it to the machine shop or workshop I choose to attempt the repair. I’m sure they would have used cutting mandrels, whereas I didn’t even know they existed before you pointed it out.
