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Originally Posted by WhiteCrane
General questions about turbochargers. I'm talking about stock turbos, not HUGE after market turbos. Do they cause maintenance issues in a vehicles old age? Do turbos themselves break around 100k? I've heard its not uncommon for turbos to stop working or leak despite proper maintenance once the car is old. And that if you are buying a car for longevity, to always go naturally aspirated. Any truth to this?
I am contemplating buying an old Saab 9-3 2.0 turbo. Always been a Saab fan. I know their drive trains are solid, but turbos worry me.
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Newer turbo systems are pretty damn good. I ran 135K on my subaru at stage 2 (higher boost pressure/turbo rpm/temp) and didn't have any problems. On any modern decently designed car there is going to be an intercooler and the engine components will be designed to take the additional heat of the induction air. My turbo was oil and water cooled, and when you turned off the car the coolant would evaporate, gasses would get drawn above, which would suck more coolant into the turbo from below, and due to the fact that the coolant would not be rapidly cooling off at that point, it allowed for a gradual cool down, much like a "turbo timer" would, although as a rule I still wouldn't drive "all out" right before shutting it off.
Realize a few things though, older turbo cars can be a headache and pain, with excessive lag, poor cooling and sometimes no intercooler (causing excessive wear and heat soak), and when that turbo "goes" in the most extreme case it can grenade the compressor and send metal chunks into the engine and kill it very quickly. Not very common on any modern car, but if your talking old and tired, that may be it. Usually a way to tell this is based on how much oil the thing eats, as the more oil it uses usually the more worn down the turbo is and sometimes finding oil in the intercooler is another way, but it's not like you check that often. It's also nice if you have a car with a boost gauge where you can see if it's making the proper boost, otherwise sometimes you are losing some to worn components and hose-leaks.
I wouldn't say a NA car is necessarily any better for longevity when compared with an equally well-designed turbo car, but there have been some crappy ones in the past. Saab sold the subaru impreza wrx as the saab aero-something-9-or-other, don't remember which one it was. You might have an old NA car about to explode it's transmission or have a head-gasket failure, or the end-game timing belt. Remember that some turbos can even be rebuilt, or you can pick up an OEM style with little use for cheap from people that have upgraded. May be worth it if you plan to keep the vehicle.