Oil Pressure Switch Stripped Cylinder Block Threads

[shark.taco]

Title is pretty self-explanatory. I honestly don't know how it happened. I hand-threaded the switch on and tightened using my torque wrench. When it wouldn't tighten I knew I was in for a world of hurt. Sure enough, I back it out and found pieces of threads sheared off. My first plan is to rethread the cylinder block, put thread tape around the switch, and see if that tightens to spec and holds oil. Plan B is to drill in new larger threads and use a threaded insert. Either way, I'll pull the valve cover off and clear out any metal shavings. Does anyone have any other ideas?

[Mike W.]

M20 I'm guessing? Not that I think there's any practical difference but you said block. I had similar with my first BMW, a Bavaria, which screwed into the aluminum head. I could get it hand tight, but not much more. Making sure I didn't get any in the pressure port, I cleaned it with probably carb cleaner, but apparently brake cleaner is better, then globbed epoxy on. Probably JB Weld, but maybe something else, but "steel" repair, though I'm not sure there's any difference besides the color. I did have to take it out once, I forget why, and putting a socket on it, the epoxy broke easily enough, but I put a lot of miles on it, 50K? with no issues. I would use a brand new, quality OP switch, they can leak as they age.

I would not use teflon tape, yes it seals, but it's got no strength so you could be at risk of blowing it out. But just glue that sucker in there.

[szacsi72]

It really doesn't need a lot of force. You could try high quality thread sealer-locker (loctite), in that case you would not need to tighten it as much, since you don't need the copper to seal. Loctite also offers a liquid thread repair kit.

I would avoid drilling etc. if it's mounted on the vehicle..

[BMWCCA2]

Assuming you were using the correct part?

[shark.taco]

M20 I'm guessing? Not that I think there's any practical difference but you said block. I had similar with my first BMW, a Bavaria, which screwed into the aluminum head. I could get it hand tight, but not much more. Making sure I didn't get any in the pressure port, I cleaned it with probably carb cleaner, but apparently brake cleaner is better, then globbed epoxy on. Probably JB Weld, but maybe something else, but "steel" repair, though I'm not sure there's any difference besides the color. I did have to take it out once, I forget why, and putting a socket on it, the epoxy broke easily enough, but I put a lot of miles on it, 50K? with no issues. I would use a brand new, quality OP switch, they can leak as they age.

I would not use teflon tape, yes it seals, but it's got no strength so you could be at risk of blowing it out. But just glue that sucker in there.

M30 actually, probably meant to say cylinder head. It happened as I was installing a new switch I like the epoxy idea though. Good to know that it held for so long.

Assuming you were using the correct part?

I think so. I bought this from FCPEuro. Comparing to the original, it all looks the same or very similar. On RealOEM it show it as a valid part number.

I pulled the valve cover off, hoping to see the through hole, but no dice. The hole goes directly into the cylinder head, so I'm super hesitant to drill or rethread at the risk of pushing metal shards into the engine. I'm thinking I'll go for either the liquid thread repair or epoxy and pray for the best. I appreciate the suggestions, I'll report back on what I end up doing.

[shark.taco]

I picked up some J-B Weld High Heat Epoxy, rated for 550° and is "Great for Engine Blocks" so I figured it fit the bill. I cleaned out as many metal shards as I could using a pick and rag, applied the epoxy to the threads of the switch, and hand tightened. I'll update if it starts leaking or if after a while it stays sealed.