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no boost?

New here,first post owner for 24 years of 86 911 turbo 38,000 miles.Got on it in first entering highway lifted to shift to 2nd and motor was flat no boost,runs fine no noises just moves the boost needle a little in first? any help,wast gate stuck,bad turbo??Thanks

Old 09-22-2010, 10:18 AM
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Originally Posted by 5050racing View Post
New here,first post owner for 24 years of 86 911 turbo 38,000 miles.Got on it in first entering highway lifted to shift to 2nd and motor was flat no boost,runs fine no noises just moves the boost needle a little in first? any help,wast gate stuck,bad turbo??Thanks
If you reached full boost in 1st before shifting to 2nd, then your wastegate may be stuck open. Your description says the car is running fine other than lack of boost, so that would rule out any boost plumbing leaks presumably. I would suspect a bad turbo as the very last thing.
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Old 09-22-2010, 10:58 AM
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Thanks for the help,sorry to repost didn't see how fast the topic dropped .Checked relays and switched with other one from up front,no change.You can hear it but just .2 boost.What is it like pulling waste gate apart? I do all kinds of work on the farm equipment and alike,1/4 midgets,dirt bikes,any help ahead of time will be nice thanks.
Old 09-22-2010, 12:19 PM
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Thanks for the help,sorry to repost didn't see how fast the topic dropped .Checked relays and switched with other one from up front,no change.You can hear it but just .2 boost.What is it like pulling waste gate apart? I do all kinds of work on the farm equipment and alike,1/4 midgets,dirt bikes,any help ahead of time will be nice thanks.
The relays I presume refer to fuel pumps and such? They won't have an impact on whether or not your car builds boost, unless you've got poor engine running performance due to poor fuel delivery or ignition...in which case you would have other symptoms beyond no boost.

The WG is easy to pull off....4 bolts where it mounts to the exhaust, and the boost signal hose are all that needs removed. There's a big valve in there (looks just like an engine head valve) that's held closed against it's seat via spring tension inside the WG housing. If the valve guide is corroded, or the seat itself, not allowing the valve to fully close, then it will "waste" exhaust pressure that ordinarilly would be turning the turbo.

Try this: Stuff a wad of paper into the WG muffler (if installed) or the WG exhaust pipe, and start the car. If the WG is not sealing closed, it'll blow out that piece of paper when you rev the engine. And/or, you can bench-test the WG once it's off the car by applying about 15 lbs of air pressure and seeing if the valve opens...if it isn't already open indicating it's stuck.
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Old 09-22-2010, 12:43 PM
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thanks I was going to have someone rev it for me and listen but nobody home that a great idea thats why I asked.Let u know
Old 09-22-2010, 01:00 PM
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Didn't dislodge the rag,not jammed in to tight but snug quick rev to 5000 or so .Any other ideas?It runs fine smooth,I drove it just not a lot of power?
Old 09-22-2010, 01:13 PM
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Didn't dislodge the rag,not jammed in to tight but snug quick rev to 5000 or so .Any other ideas?It runs fine smooth,I drove it just not a lot of power?
The boost recirculation valve internal piston may be stuck open. It should only open in response to engine vacuum when you're suddenly off the throttle (during shifts and/or at idle). It should close once the throttle is opened and allow boost to build as opposed to recirculating back to the front of the turbo. It's a simple spring loaded piston within the housing situated left and back of the intercooler. Has a big 1/2" vacuum hose connection on one end that drops down to the intake manifold. Take it apart, clean and inspect.

You could also pull the turbo compressor intake hose off the turbo and visually inspect the compressor wheel for damage, and check to see that it spins freely.

If all that checks out, then something else is causing the engine to run with less power, not generating sufficient exhaust gas pressure to spin the turbo enough.
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Old 09-22-2010, 01:41 PM
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Thanks again I will look at what you said,it runs to good to be major,I hope

Last edited by 5050racing; 09-22-2010 at 02:11 PM..
Old 09-22-2010, 02:08 PM
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thanks I was going to have someone rev it for me and listen but nobody home that a great idea thats why I asked.Let u know
Supercharged motors can build boost in neutral.

You can probably rev a turbo in neutral right into the rev limiter without building ANY boost at all, even on a perfectly running car. They need load to build boost.
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Old 09-22-2010, 02:21 PM
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Originally Posted by spuggy View Post
Supercharged motors can build boost in neutral.

You can probably rev a turbo in neutral right into the rev limiter without building ANY boost at all, even on a perfectly running car. They need load to build boost.
So true, but the "potato in the exhaust pipe" test was to see if the wastegate was stuck open, allowing exhaust gas to escape instead of following the desired path to the turbo. All irrespective of building boost.
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Old 09-22-2010, 02:37 PM
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I understand,he was trying to help good point though, some exhaust would leak through the wast gate if it was stuck open.
Old 09-23-2010, 07:20 AM
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Left and back of the intercooler is that looking at the rear of the car,I'm sure I will find it haven't looked yet.
Old 09-23-2010, 07:24 AM
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Left and back of the intercooler is that looking at the rear of the car,I'm sure I will find it haven't looked yet.
Here's a picture of the entire manifold that houses the recirculation valve. There are two cast caps bolted to each end of the assembly. (Note: this picture needs to be rotated 180 degrees counter-clockwise for it to be in the proper orientation as it would appear on the engine).

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Old 09-23-2010, 10:02 AM
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Nice pix,the 4 bolts,or nuts is what needs to come apart ?where is the piston and spring,under the 4 bolts or does it ride inside one of the big holes thats apart already?

Last edited by 5050racing; 09-23-2010 at 11:17 AM..
Old 09-23-2010, 11:02 AM
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Check out this thread:
Changing 930 dump-gaskets, pictures galore
Old 09-23-2010, 11:16 AM
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This forum is a great resource. Spend enough time researching and you'll find pictorials for almost everything.

The first time I took apart the valve, I was able to extract the piston and spring by just removing the cap nearest to the rear of the car...but just barely 'cause of other "stuff" in the way if I recall. My point: You may not have to remove the entire manifold to get the piston out.

550racing, please realize that even if you go through all the work, this may not be the issue with your lack of boost. I can see how the piston might eventually become stuck in the closed position if long periods of non-use, but getting stuck in the open position seems unlikely since it's under constant spring pressure to keep it closed. Unless the spring broke (unlikely, but who knows?). Just don't want to send you on a witch hunt. Do take a look at all the other suggestions as well. You'll find the issue sooner or later and become an expert in the process.
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Old 09-23-2010, 12:24 PM
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spring

I was thinking if I hear the click clack noise sounds when hitting the throttle that it"s moving,so the easer thing to check is the turbo that it's free then tear the rest apart.Not a wast of time I will learn whats in there and see whats going on like the gasketsThanks!!
Old 09-24-2010, 07:59 AM
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turbo

Just pulled the boot off of the turbo and spins free but looked in the exhaust pipe and a little oil and of fine aluminum dust not good but better than internal motor trouble I hope.NOW WHAT is that what it sounds like the problem is BAD TURBO , the car it all stock put same back on???
Old 09-25-2010, 07:52 AM
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Sure you're seeing aluminum dust? Is it non magnetic?

There is no aluminum in the hot side of the turbo, and no aluminum going backwards from it untill you get to the cylinder head exhaust ports, combustion chambers, and pistons.

The hot side housing of a 3K turbo is cast iron, the turbine shaft is steel, the 2 turbine shaft bearings are bronze, and the turbine wheel is a steel alloy.

I don't know what muffler you have but they are usually steel or stainless steel.
Old 09-25-2010, 08:05 AM
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dust

I will check if magnetic

Old 09-25-2010, 09:14 AM
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