Intermediate Shaft bearings and hot-tanking

[E30-TourZing]

Hello all,

I am just getting the final details worked out before bringing my M20 block to the machine shop on Friday. I have been informed by a few people to look into AUX shaft bearings and its relation to destroying the bearing when being hot tanked.

So far I seem to get a few results. So here is where I am at.

My motor has low original KM's, and the bearings look/feel fantastic. I intend to gauge it this week before dropping it off, but so far if I had to assemble this motor tomorrow, I would not be worried about those two bearings failing.

A few people have mentioned to just leave the aux shaft in, and that may keep the bearings safe as long as its not dipped for an extended period of time.

Ideally this would be my chosen route. Can any of you fine folks speak from personal experience?

If it has worked for others in their rebuild, can anyone advise me on tips to give my machine shop so they lower the chances of making the mistake?


Thank you for your time!

[JehTehsus]

One thing I may or may not have mentioned over text earlier, my machinist did not hot tank the block (I discussed the bearing issue with him extensively). He said they were fine to clean it and that it would turn out 'just fine' especially given that I planned on painting. My other options were get another machinist who is familiar with the bearing or try to get them to work out the bearing (decided I would rather put the money towards a dry sump configuration). For the record, my motor does have high mileage and I am not at all 100% happy with the state of those bearings in my engine... but they will have to be fine for initial break in and setup.

Not sure exactly what cleaning process they went through, but it definitely did turn out fine, even if it was a bit more work on my end for painting prep because the exterior rust was not stripped. I hit the bare block with a wire-wheel and then some paint and IMO it looks pretty great for my amateur efforts. Internally they punched out all the plugs and flushed everything, not sure what they hit it with on the inside but I did not notice any internal rust at all, only some corrosion around the coolant ports where rust had clearly once been (supposedly 400kkm on the block).

Here is the block immediately after getting it back from the shop. You can clearly see all the rust.



2-3 hours later (wasn't really counting, may have been 2-3 beers later actually)





So if you aren't adverse to spending a little extra time, I would say I had decent results without doing the hot tank. IMO probably would have been more of a headache getting the bearing machined, especially if yours are in decent shape.

Anyway, if you do make it out this weekend I'll show you what I can. Head is on so you can't really see much though.

[zaq123]

why hot tank it? Oil gallery is easy enough to clean on these blocks? Just have machine shop do their thing (boring it?) get it back, clean it well and start building

[Lugnuts]

A few people have mentioned to just leave the aux shaft in, and that may keep the bearings safe as long as its not dipped for an extended period of time.

This is what I had done on my M20 block that's sitting on the stand in my garage. I supplied it with the shaft installed and locked in place. The bearings look fine. I don't think they're put under a lot of stress over the life of an M20...if they're visibly mangled that's a different story.

I don't know exactly what type of hot tank they used, there might be different types? I think the common type is heated caustic soda, which as I understand is bad news for non-ferrous metals. There's also the jet-spray enclosure type...no idea what they use as a cleaning agent.

The shop that did my block deals primarily with E30 engines, and they're fully aware of what a pita it is to replace the bearings. I've been through that once before and will try and avoid having to do it again personally!

I'd be inclined to measure the clearances for peace of mind.

Related to this, there's a small thread-needle bearing that sits in the block, under the silver BMW cap on the side of the block - you can gently push it out (from underneath) with a 10mm(?) long socket. I believe they're NLA, so you might want to consider removing:

P/N 23: https://www.realoem.com/bmw/enUS/sho...diagId=11_0117

And as zaq123 said, consider also removing the oil gallery plug (only the front one is necessary) to ensure the block can be thoroughly cleaned before assembly. Might want to remove it before giving it to the machine shop...if you go ahead with the tank.

Replacement gallery plug is P/N: 4 on the above link.

Link to my removal of the gallery plug: https://www.r3vlimited.com/board/for...or-to-assembly

Personal tip...take lots and lots of photos of EVERYTHING you supply to the machine shop...knowing what you hand over is scratch/defect free helps avoid any surprises when you get it all back...personal experience.

[JehTehsus]

...

Related to this, there's a small thread-needle bearing that sits in the block, under the silver BMW cap on the side of the block - you can gently push it out (from underneath) with a 10mm(?) long socket. I believe they're NLA, so you might want to consider removing:

P/N 23: https://www.realoem.com/bmw/enUS/sho...diagId=11_0117

...

I think the bearings are still available, I managed to get a replacement without any issues.

[Lugnuts]

I think the bearings are still available, I managed to get a replacement without any issues.

Nice, that's good to know :)

[reelizmpro]

Everything pertaining to the IMS bearings is still available. I just received new needle bearings and IMS bearings. Price has gone up to $20-30 per bearing though. They must be running low. Anyway, my old bearings still look great and I'm tempted to leave them be.