Saab Central - Technical Help
Classic Saab 900: Turbo Rebuild guide (1) 2
This article kindly written and supplied by Pat Price
1. Do not remove the exhaust housing from the car if you do not have to. Separate the turbo centre section from the exhaust housing in the car this will lower your chances of breaking bolts.
2. Mark the sections carefully BEFORE disassembly do not use a marking pen use a hammer and punch as any faint marks will be removed in the cleaning process. There are no indexes between the sections and you can assemble them in any position. Trust me here I forgot only once.
3. When removing the compressor wheel from the shaft do not hammer on the end of the shaft as you will bend it. Very rarely it will slip off after removing the nut if not you will have to have it pressed off.
4. Clean out the supply and return lines carefully. Usually not a problem unless your turbo is completely clogged up.
5. When you are cleaning the main body casting in the centre section pay very close attention to the passages outside of the exhaust side bearing this area seems to take the worst of the clogging and will look clean. Make sure to dig around to be sure that all debris is removed here also run a wire through all passages in the housing.
6. Where the pages call for Caterpillar high vacuum lube you can use any good stiff silicone lube.
7. The little seal that goes on the shaft at the exhaust side of the shaft is easy to crush or destroy as you have to push the shaft into the housing blind[the heat shield gets in the way you have to do this by feel it takes a little bit of effort to get it wiggled in there. Just be aware and don't get too heavy handed. PS this is the seal that is leaking in your case so be very vigilant in cleaning the groove in the shaft. You can use a broken off piece of the old seal ring here.
8. There are really only two failures that cause smoking in a turbo. Smoking at idle is caused by the exhaust side seal getting worn out. As the boost increases the pressure in the exhaust system increases and the oil is forced to stay in the turbo by the exhaust pressure. The other failure is when the oil drain on the outside of the rear bearing gets clogged and the pressurised oil is forced past the seal into the exhaust. This smokes so much that your car looks like it is on fire. Worn bearings can contribute to this but usually it is just clogging due to the oil burning off leaving solids behind. If you study the path of oil through the unit you will see that at no time are the seals expected to restrain the pressurised oil from the engine. It is really a simple elegant piece of equipment.
That is about it basically just clean it out really well and don't force anything.
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