Exhaust leak - from turbo downpipe? Need help diagnosing

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DecalService
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Exhaust leak - from turbo downpipe? Need help diagnosing

Post by DecalService » Sun Apr 29, 2018 3:03 pm

Hey there guys,

Just today I noticed a prrrt-prrrt coming from the area on the turbo where the butterfly valve linkage is, under the turbo. It gets hot real quick and I can't investigate further without burning my hand, so I wanted to ask:

What are the possible suspects to look at?

I'd like to add that it is at its worst when cold started, better when warm, and very, very slight leak when engine is at normal operating temp.

I'm considering buying an endoscope to get down under there a bit better. and see the issue on my computer screen. The car is SO low that I even have trouble getting it on ramps, let alone sliding underneath it.

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Re: Exhaust leak - from turbo downpipe? Need help diagnosing

Post by thesameguy » Sun Apr 29, 2018 3:59 pm

That 5-bolt joint is prone to leakage with age - I think it's ATP that sells a metal crush gasket to help fight it. I've also rarely seen the actual swing gate arm leak, though usually that's on cars that have sat for a long time. Your leak could be from somewhere else, too, such as the turbine housing or the joint between the elbow and downpipe. The only way you'll know is by looking... car on stands & a creeper.

Ed Lijewski
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Re: Exhaust leak - from turbo downpipe? Need help diagnosing

Post by Ed Lijewski » Sun Apr 29, 2018 5:18 pm

At least check the waste gate actuator vacuum/pressure hose for integrity.

YMMV
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DecalService
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Re: Exhaust leak - from turbo downpipe? Need help diagnosing

Post by DecalService » Mon Apr 30, 2018 1:35 am

Thank you guys!

Could post-turbo exhaust leak possibly cause some idling or driving issues? I noticed that it idled a bit oddly today, but evened out after it warmed up. Could be that I need to drive it more. I drive it only twice a month usually. Car has 44k, and had lived a very sheltered life. Any reason why I shouldn't drive it for a few miles this weekend? There's a little gathering I'm planning on joining.

Appreciative,
Rod

DecalService
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Re: Exhaust leak - from turbo downpipe? Need help diagnosing

Post by DecalService » Sun May 06, 2018 3:10 pm

Bought an endoscope, took a deeper look, and for the life of me, I cannot tell where this damn leak is coming from. There's pressurized hot air flying between the turbo downpipe (flange area where it mates to exhaust) and the back of the turbo. I can't tell if it's coming from the flange or the exhaust side of the turbo. I'm open to any suggestions to figure out where it's coming from. This bastard gets so hot so fast!

Any tricks you guys have come up with to identify the location of the leak on a hot exhaust? I usually try soapy water, but that won't work here, so only option I can think of is to use a silicone glove. The good news is that the leak stops after 10 minutes of running, presumably due to metals expanding.

DecalService
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Re: Exhaust leak - from turbo downpipe? Need help diagnosing

Post by DecalService » Sun May 06, 2018 3:29 pm

Bought some aluminum tape. Will block off the flange and try again. If no dice, then I'll block off the back of the turbo. Hoping I can at least find out if there's a crack or if the flange just needs a new gasket or some tightening. Will report back. Thanks guys.

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Re: Exhaust leak - from turbo downpipe? Need help diagnosing

Post by thesameguy » Sun May 06, 2018 7:28 pm

DecalService wrote:
Mon Apr 30, 2018 1:35 am
Could post-turbo exhaust leak possibly cause some idling or driving issues?
Definitely... with no boost is present, an exhaust leak can suck in air, messing with the 02 sensor readings and your mixture.

DecalService
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Re: Exhaust leak - from turbo downpipe? Need help diagnosing

Post by DecalService » Mon May 07, 2018 1:11 pm

That's a great point. Since it's pre-O2 sensor leak, it could cause poor readings. I appreciate you "waking" me up to this fact. I knew it, but I just didn't even realize it until you said something. Shame on me, been working on cars for 20+ years and I go and disregard something as simple as this.

I'll report back once I dig a bit deeper into the issue.

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Re: Exhaust leak - from turbo downpipe? Need help diagnosing

Post by hEaT » Mon May 07, 2018 4:55 pm

If you do decide to remove the downpipe/elbow and haven't before, be very careful with those bolts. Those tiny M8s from all the heat cycling love to snap off with minimal effort. Turns a simple job into yanking the turbo out to drill them.
Joe
1985 Nimbus Grey XR
2017 Ford Focus RS

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Re: Exhaust leak - from turbo downpipe? Need help diagnosing

Post by thesameguy » Mon May 07, 2018 5:55 pm

aka "lots of Kroil."

:D

DecalService
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Re: Exhaust leak - from turbo downpipe? Need help diagnosing

Post by DecalService » Wed May 09, 2018 4:52 pm

Thanks guys! Solid advice. I've rebuilt only 2 turbos, both on Volvos, a 760 and a 242. Both were a pita due to the heat in that area causing bolt issues. I'm sure it's the same or worse here.

The car is in close to perfect condition, with only 44k miles. Seats still look and feel new. I'd hate to go tampering with it and then have to put a new manifolds possibly a turbo on. The turbo shaft and bearings are in crazy good condition with almost zero play. The only issue is the slight exhaust leak. Something is telling me to leave well enough alone or maybe just get the hole welded shut if I can find it... IF and ONLY IF it won't interfere with the removal of turbo and pipe components later. I'd hate to break a bolt and have to refit/replace a turbo or otherwise healthy manifold. There's only a slight seepage with no visible crack or hole... yet.

The car only gets driven about 5 miles a month. Shame on me for not driving it more, and I'm wondering if this is the cause of the leak that has developed, but at least I'm religious about starting it and maintaining it, and letting all the rubber including tires get some exercise. She just got a fresh change of Royal Purple and filter last week, along with all new belts. Out here in West Texas, the roads don't allow you to drive a lowered car, and I'm not about to remove the nice Bilstein B8 sports and Rapido springs =)

Will write back to update!
My appreciation....
Rod

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Re: Exhaust leak - from turbo downpipe? Need help diagnosing

Post by Ed Lijewski » Wed May 09, 2018 7:22 pm

If you decide to take off the elbow, it's an odds on Vegas bet that 3 or 4 or all 5 of the bolts will snap. IME.

YMMV
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Re: Exhaust leak - from turbo downpipe? Need help diagnosing

Post by my8950 » Wed May 09, 2018 9:02 pm

Ed Lijewski wrote:
Wed May 09, 2018 7:22 pm
If you decide to take off the elbow, it's an odds on Vegas bet that 3 or 4 or all 5 of the bolts will snap. IME.

YMMV
Right, it's not about if they will, it's how many will. ;)

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Re: Exhaust leak - from turbo downpipe? Need help diagnosing

Post by thesameguy » Wed May 09, 2018 11:20 pm

Use LOTS of Kroil. Like a sick amount. Use an entire can. Turn the entire turbine housing red. Apply liberally over several days. Dollars to donuts all the studs will come out - whether that's out from the housing or the nuts comes off, one way or another. I haven't had a bolt break on a T3 in over a decade. Lots. Of. Kroil.

When you're putting it back together, order new M8 studs and locking copper nuts from ATP Turbo. It's $10 worth of hardware and $10 in shipping, and you'll be fine next time you need to take it apart.

IME, on XR's the bigger issue is the two bolts into the elbow from the downpipe. Big threads, poor access, and odd-sized bolts. FWIW, McMaster-Carr DOES carry them, but they are about 1/4" too short for ideal. They work fine, though, plenty of engagement.

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Re: Exhaust leak - from turbo downpipe? Need help diagnosing

Post by Ed Lijewski » Thu May 10, 2018 6:58 am

I have and use Kroil. Better than over-rated PB blaster IMO. But it doesn't work miracles IMO.

YMMV
Descartes: "Cogito Ergo Sum"
Lijewski: "Sum Ergo Drive-O. Mucho!

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