SNAFU; high performance 318is build that lives up to the name, Turbo M42 ➞ Turbo M20

[varg]

Can't catch a break this year. I discovered excessive turbo shaft play a couple of weeks ago, it was almost trashed with ~5,000mi on it. Installed an oil pressure gauge to see if low oil pressure had killed this freshly rebuilt turbo and it read 0 at idle, so I tossed that piece of junk and spent more on a nicer one, oil pressure was reasonable with that one and my in line filter didn't have significant pressure drop so that kind of narrowed it down to a faulty turbo rebuild. At that point I really had no choice but to buy a new turbo, so I did, and sorted out a permanent and safe oil feed solution to get rid of the in-line filter by having a local hydraulic shop weld a fitting to the oil cooler banjo bolt and cramming the stock oil cooler under the radiator temporarily. I had it done before Cars and Coffee last Sunday and that was fun but the fun stopped the other day. I turned the boost back up and my clutch started slipping. The clutch is 3 years old and it has maybe 60k miles on it, I guess it just couldn't take the daily duty in traffic. No time to do the clutch now with exams coming up so that's twice in a year that my car will be out of service for a couple of weeks. My transmission leaks pretty badly too so I'll be replacing whatever seals are leaking while it's out. Not sure what clutch I'll go with this time around but whatever it is I'm hoping that with everything sorted out I don't have any problems with this car for a few more years.

[nando]

You don't have to helicoil. you drill and tap for the larger stud end. i think it's an M10, if the stock stud is M8.

But yeah drilling through that hardened steel stud sucks.

[varg]

Yeah, I've seen those and considered them as the solution to this problem, but I really didn't have time to keep drilling away at it then wait for the stud and proper size helicoil kit to arrive. Progress was so slow, I would get fractions of a millimeter of drilling progress out of every tank of air then have to wait 15-20min for my relatively small air compressor to cool off before refilling the tank. I'm guessing there's 3-5mm of partially drilled out stud left in there, and I can get to the hole with the downpipe removed and the header still mounted to drill an oversized hole in the future so at least there's that.

[nando]

they make double-ended studs where one side is larger than the other. Basically for your exact same problem, where you had to drill out a hole in the head. I used these on my M20 back in 2006 for a couple studs where the shop that had 'rebuilt' the head stripped them out.

I bought a whole box of them. I wonder if I still have them laying around somewhere..

[varg]

do you regret going boost?

No. These issues really came down to something beyond my control - if the header hadn't cracked so severely or had a warped flange in the first place none of this would have happened. The warped header working the hardware loose as it heat cycled is what prompted the stud replacement, had the header been a put it on and forget about it deal like I was expecting the old hardware with its seized up nuts never would have been an issue. If I did it again I would skip the M20 and go straight to a built 302 though, I could have as much power or more with more torque across the rev range, better reliability, better sound, superior NA response...

[efficient]

do you regret going boost?

[varg]

The car is back together. I gave up on getting the stud out, made drilling progress with carbide tipped masonry bits but the bits wandered so much that the hole wound up oval and oversized so my M8 helicoil tap just wasn't going to cut it. Ran out of time to deal with it and had to get the car back together so I could use it. The replacement header flange is warped too, just not as badly as the old one, so I'm guessing it's just a matter of time until the exhaust starts leaking at cylinder 6 where only the bottom of the flange is clamped. Also replaced the disintegrating turbo blanket with a crappy bent piece of E30 heat shield. Very fitting.

[varg]

It's a hardened stud, there's no getting anything done to it with hardened steel tools, it blunted my punch when I tried to make a divot to start drilling and it kills 5% cobalt bits. I only made any good progress with a carbide tipped tile/glass bit which eventually shattered. Too busy with school to work on it now, maybe I'll finally get through it next weekend. Even hollowed out (drilled most of the way through) the damn thing won't budge with a weld, I figure I can't fill it with weld effectively because I'm welding with fluxcore and there are too many voids created by the flux vaporizing. Next step is to try a better carbide tipped (masonry) bit and try to get completely through it, then progressively larger bits until there's almost none of the stud left. Couldn't dissolve it out because nothing would seal a heated reservoir of alum solution to the oil-saturated aluminum head without leaking, tried clay, silicone caulk, hot glue, rtv. All leaked. Had I been able to get it to seal it would've been dissolved by now, I know it does work because I dissolved part of the broken off stud in a measuring cup.

[econti]

drill up the middle, hit with an abuse flatblade until it makes a flathead shape, then undo
unless of course it's right up in the gooch area between block and strut tower which it no doubt is

[varg]

I don't do easy outs because of the chance that one will break, they're way harder than this already hard steel set screw and you're in a world of hurt if you have to remove a broken off easy out from a limited access area like this. I'd either have to pull the head and have a shop fix the problem or try the 'dissolve steel out of aluminum by immersing in heated alum solution over a long period of time' trick. I once saw this done by attaching a cut open aluminum can filled with alum solution to an aluminum block with clay and tape, with an incandescent light underneath it for heat. It took a few days but it dizzolved the busted off tap right out. I'm reminded of an old dupont advertising slogan that became the name of a Fatboy Slim album; "Better living through chemistry"

[TeXJ]

ouch man, would an Easy-Out help get them out?

[varg]

Ah this weekend. It started as a fixing a simple thing, a blown out turbo gasket caused by fasteners that won't stay put:



Then this happened:



And then this:



All because this stud showed up in a search for "m8x40 exhaust stud":



I didn't bother to look up 45H steel, which is a set screw specification, and according to ISO898-5 "The use of set screws of hardness class 33H and 45H under tensile stress (axial or bending) is not recommended." For a project in school, or in my future job as an engineer I'd definitely have looked into this 45H spec before ordering, since it would be my job to double check something like that, but since this was "just hobby stuff" I didn't and here I am. I spent a few hours trying to weld a nut to the stud and back it out last night and failed, I need to get some nuts that aren't contaminated beyond what a wire wheel can fix. Now I'm working on stuff for school and don't know if I'll have time to fix this before the school week starts. I'm so glad I couldn't replace the other studs when I got my new hardware in months ago because I couldn't remove them without taking the header off, they may have all broken because I was torquing them down pretty tight to compensate for a warped header flange. The stud didn't break when I torqued it down, it stretched, and when I went to remove the nut that's when it failed.

[varg]

you know, a M42 doesn't have a belt that can fail. Maybe you should swap to one of them

Yeah, it's really too bad that just about everything else about it is crap :giggle:

[econti]

you know, a M42 doesn't have a belt that can fail. Maybe you should swap to one of them

[ForcedFirebird]

#8 in the link is the "inspection cover", but it won't help much for the tensioner...

https://www.realoem.com/bmw/enUS/showparts?id=1113-USA-01-1991-E30-BMW-325i&diagId=11_0405