89 740 possible turbo fail?

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Old Jun 18, 2018 | 04:22 PM
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fecal jesus's Avatar
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Default 89 740 possible turbo fail?

So I recently got an 89 Volvo 740 turbo with about 194k miles on it. It has been running just fine but about a week ago I was driving on the highway and switched to a/c to cool off and I heard a whine from my engine. Now whenever the turbo starts to engage (when the needle on the dash goes into the colored turbo section) the turbo won’t seem to engage and my car won’t accelerate or maintain highway speeds. It still runs and can drive at low speeds. The air mass sensor is clean on both ends. The air hose from the inter cooler to turbo is clean but appears to be collecting grease on the underside from somewhere. That’s all I’ve done so far to troubleshoot the issue. Is my turbo dead or is there something I can do?
 
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Old Jun 18, 2018 | 06:11 PM
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make sure the high pressure hose coming out of the turbo to the intercooler isn't blowing a leak under positive boost. I had that problem with my 92, the silicone hose was mushy, and wasn't staying under the clamp.. drove fine without boost, but when it was boosted, lost all power.
 
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Old Jun 19, 2018 | 03:27 PM
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Originally Posted by pierce
make sure the high pressure hose coming out of the turbo to the intercooler isn't blowing a leak under positive boost. I had that problem with my 92, the silicone hose was mushy, and wasn't staying under the clamp.. drove fine without boost, but when it was boosted, lost all power.
so I checked that and it’s getting good air flow. Tried driving around block and noticed the turbo would be loud and spool up but then immediately could hear the whoosh of the pressure releasing. Also, could piston misfire possible be a reason affecting this?
 
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Old Jun 19, 2018 | 03:39 PM
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if the 'pressure is releasing', it has to be going somewhere. if it only fails under positive boost, it could well be a nearly invisible crack that gets opened up under boost pressure, but is normally closed. I'd check the whole air path from the turbo through the intercooler to the throttle body... check the intercooler itself. check the idle air hoses, and other larger diameter vacuum hoses...
 
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Old Jun 19, 2018 | 03:54 PM
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Sorry as I am really new to this, but what is the best way to go about checking all the lines? I've tried looking up a variety of ways but it's pretty hard to find info regarding this.
 
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Old Jun 19, 2018 | 05:00 PM
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visual inspection, a bright light, use a mirror to see the undersides of things, wiggle/squeeze stuff to see if its cracked, etc.
 
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