Stripped oil pressure sender

[mike_gee32]

I've managed to strip the oil pressure sender thread between the pushrod tubes while changing a previous owners failed sender relocation bodge for the Brickwerks one.
I had real trouble getting the thread started as the hose was pushing the banjo fitting to one side but managed it by holding the fitting with long nose mole grips and using a deep socket hand held. the first four or five turns went in easily then I had to remove the mole grips to carry on tightening with a ratchet handle, I'd guess about half way in it got a bit harder to turn (which I put down to the resistance of the hose pulling to the side) then once home it's continued to turn without fully tightening. Cranking over and oil is squirting out

I can't find much info about solutions to this online - there is a thread on the samba which talks about using a 1/8 NPT tap (https://www.thesamba.com/vw/forum/viewt ... p?t=618502) but it looks as though the op managed to clean up the original thread enough to reuse a m10 fitting so i don't know if it would work. Presumably as NPT is a tapered fitting I could fit an adapter in then the banjo bolt tightens against that.

I can't find NPT to M10 adapters in the uk so I'd be ordering from the states, BSPT taps and adapters are easier to come by but I don't know if they'd need the hole drilling larger first.

Access with the engine in is limited, I can probably get a tap in there but not if I've got to drill as well.

I'm also worried that i'm likely to get swarf and debris in the oil-ways, I'd rather not have to split the case as I can't afford a proper rebuild at the moment.

Part of me thinks that I've nothing to lose trying as the engine is knackered as it is...

Any comments, suggestions, or offers of dirt cheap running engines appreciated

[itchyfeet]

You can but a remote T piece with NPT converted to another thread.
or try an M10 taper adapter it may work.

[937carrera]

Do you think you could get a helicoil in ?

It will involve drilling and tapping there are things you can do to minimise risk of swarf.

Alternatively, you could stick some chemical metal in and retap......... you would need to be patient and it may not be successful

[itchyfeet]

It will involve drilling and tapping there are things you can do to minimise risk of swarf.

yes but the consequence could be very bad, there is a risk of swarf with an taper thread also but much much less.

[mike_gee32]

Thanks for the replies, I'd rather not use a helicoil as I doubt I could fit it with no swarf falling inside - and the engine will definitely have to come out to get a drill in square. Might be the final option though...

I'd considered chemical metal but I reckon getting everything oil free enough for it to stick will be hard and there's a high risk of blobs going in the engine.

Think I'll order an adapter and see what it looks like when it arrives, I've also got a block of aluminium I can try to recreate the stripped M10 in to get a feel for how much swarf might be created.

To minimise swarf entering the engine I was wondering if a few pumps of thick grease in the hole before I start might block the oilway enough that any swarf would stick to it and be pulled out with cotton buds or similar.

Presumably the oil path is pump - filter - sender - rest of engine. If it was pump - sender - filter - engine then I could flush through with the filter off to try and clear anything that's got in.

[937carrera]

Chemical metal - you don't need to use much, think of it more like extra thick PTFE tape that you can cut a thread into. You can use brake cleaner top p[repare the surface of the threads, and if you apply with a matchstick you shouldn't get any inside the case.

Retapping - yes, use grease to capture any swarf. Swarf tends to come up the drill bit and gravity is not working against you so much in this situation. You are only drilling ally, so a nice slow speed will get the job done, and not much effort needed with the tap. You could try the adapter, and if that doesn't work, you still have the helicoil (or maybe better timesert) as a fallback.

Thinking about this, you could simply leave the remaining threads untouched and chemical metal in an M10 - M10 adapter.

Use the 24hour stuff, it has a higher tolerance for temperature

[Mr Bean]

It might seem a bit of a harebrained solution to the swarf contamination problem but what about applying a controlled safely calculated low pressure air supply to the inside of the crankcase while the drilling and tapping was taking place. Or maybe if you made sure there was a free path of air into the crankcase you might get away with a nozzle bodge on the household Henry/Henrietta.

( superfluous word edited out)

[mike_gee32]

It's been a while since I started this thread, life got in the way of fixing the van, but I thought I'd update in case anyone else suffers the same problem.

Thanks for all the suggestions, in the end I ordered a 1/8 NPT bottoming tap and stainless adaptor and successfully fitted it yesterday.

I put a decent blob of grease in the hole before I started and liberally covered the tap as well, the case tapped very easily and there was just enough room to get a ratchet tap handle in which made cutting the thread a simple process. I was a little worried the hole would be too large but the tapered adaptor sealed up nicely with one thread still showing.

Looking at how much swarf was caught in the flutes of the tap and how little remained in the grease I pulled from the sender hole I'm confident very little if any made its way into the oil ways, before fitting the adaptor I cranked the engine over holding a catch can until oil flowed to flush any remaining bits out but couldn't see anything metallic in the oil so hopefully all will be well.

I've ran the engine up to temperature and its sat overnight with a piece of cardboard underneath and so far there are no drips (coming from the sender at any rate )

I can't test further now as the van is midway through a light restoration and there's still a bit of work to do till I can get it MOT'd but at least I can move it round the drive again.

[937carrera]

Thanks for coming back and posting the solution, it's good to hear a good outcome and the risks of swarf can be managed.

Funnily enough I need to do an oil pressure test on another vehicle and there's a "special tool" that you need to make a suitable connection. I have made my own just this week using an M14 flange bolt and a NPT >BSP adapter threaded through the top. Not tested yet so I hope mine is as leak free as your solution