Turbo - Re-installing
A few tips on re-installing the diesel's turbo and manifolding
Exhaust manifold to Turbo mating face
This is an important joint, which does not take a gasket from new, so has to be clean, flat and true. They won't be of course, on the one that's come off. There might even large flakes of rust between the two. Using an engineers surface scraper General Engineering Scrapers, carefully remove any rust flakes from both surfaces.
To ensure a clean and flat surface, follow this link: Techniques - Cleaning/Trueing mating faces
Attempt the same with the manifold, but this time either have to use a file if on engine, or use an emery plate as in the link above.
NB. It may be possible to get a very thin two layer stainless gasket, but should still be prepared as well as you can.
It's a moot point whether to use any exhaust paste or not, but if so, must be very thin, away from edge of exahust ports (Don't want the stuff goibng through the turbine) and the joint must be pulled up fast, before it cures.
This turbo/exh. flange uses four very expensive set-screws. They are 12 point, M-10 heat resisting flange-head screws (Mine needed a 12mm 12 point socket Hacksawbob) (about £13/each!) If you need to replace them, grade 12.9 cap-head socket screws might be good enough. Despite the qaulity, they can shear when being removed after a number of years. Ensure good second hand ones or equivalent grade socket cap-heads are used as replacements. Clean old ones up well, can use copper-slip on the threads but not under the heads. If the heads are damaged
Torques - AFAIK, about 33~36 lbf-ft (circa 45 N-m) is the right figure for the four flange-head screws, pulled up in stages.
Gotcha - You will find that is a good idea to mount the turbo's compressor inlet rubber moulding (with offset holes and smaller connection for the BOV hose) BEFORE fitting the turbo to the exhaust flange. Otherwise it is a fight you may end up losing... you may find that the fitting for the turbo inlet is perished or damaged, a nice wide hose-clip should help.
NB. Make sure the compressor outlet to engine inlet manifold hose, is insulated with a flexible ally 'concertina' hose and that both ends have a perfect gas-tight seal, using good quality hose-clips, but as always, never overtighten. Once it feels tight with a well-sized screwdriver and as long as it seems secure, leave it at that i.e. stop before the clip cuts into the hose.
The manifold should ideally have its heat-shield in place, to avoid heat-soaking both the turbo to inlet manifold hose and the compressor housing. Heat retained in the exhaust manifold will also put that bit more energy into the turbine.