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Narrowing down a boost leak- 2000 V70R

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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Narrowing down a boost leak- 2000 V70R

Post by bmdubya1198 » Mon May 13, 2019 11:34 am

I'm pretty certain the low boost issue on my 2000 R is due to a boost leak (I can hear it when the car is in boost) and I've narrowed it down to being under the intake manifold.
I have already pressure tested the intercooler piping from the turbo to the outlet hose just before the plastic hose going to the ETM, so I know the rest of the system is good. When I connect that rubber hose coming off the top of the intercooler back onto the plastic ETM hose, I hear hear a loud hissing from under the intake manifold, but it's very hard to tell exactly where it's coming from. I already replaced the check valve underneath it, so I know that is working now. I plugged the intercooler weep hole during testing, so that's not where it's coming from. When I put my head to the right of the manifold, I can smell oil when I pressurize it, then it goes away when I take the air hose off. I just replaced the ETM the other day, using a new gasket of course, and this test yielded the same results before replacing it so I don't think it's coming from there. When I move the plastic hose around the sound doesn't change, so I don't think that's the leak.

I also replaced the PCV banjo bolt with the updated version with a check valve, so I don't think the PCV is being pressurized. Of course, new copper washers on there as well to prevent a leak.

I replaced the intake manifold gasket when I did the PCV overhaul, so I don't think that's leaking. I also don't hear the leak coming from that area, it's definitely towards the front of the intake.

Does anybody have an idea of where this leak could be coming from?


1998 V70 GLT Black/Beige 193k
2000 V70R Venetian Red/Charcoal M56 Swapped 188k
2001 S60 2.4T Black/Black 230k
2007 XC90 V8 AWD Sport Titanium Grey/Black 155k
1998 S90- Silver/Gray 207k
1995 850 collection of parts... crushed... still have parts, PM if interested!
1988 744 Turbo M46 Beige Metallic/Beige 188k- Still kicking myself for getting rid of this one

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Re: Narrowing down a boost leak- 2000 V70R

Post by abscate » Mon May 13, 2019 11:46 am

What about the purge valve vacuum hose between 2 and 3?

Mine epically failed under boost


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Re: Narrowing down a boost leak- 2000 V70R

Post by bmdubya1198 » Mon May 13, 2019 12:45 pm

That one seems to be good. It’s a new hose with a new check valve.


1998 V70 GLT Black/Beige 193k
2000 V70R Venetian Red/Charcoal M56 Swapped 188k
2001 S60 2.4T Black/Black 230k
2007 XC90 V8 AWD Sport Titanium Grey/Black 155k
1998 S90- Silver/Gray 207k
1995 850 collection of parts... crushed... still have parts, PM if interested!
1988 744 Turbo M46 Beige Metallic/Beige 188k- Still kicking myself for getting rid of this one

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Re: Narrowing down a boost leak- 2000 V70R

Post by abscate » Mon May 13, 2019 1:03 pm

Have you smoked it? If you can hear the hissing, then smoke is going to show nicely.


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Re: Narrowing down a boost leak- 2000 V70R

Post by bmdubya1198 » Mon May 13, 2019 7:03 pm

abscate wrote:
Mon May 13, 2019 1:03 pm
Have you smoked it? If you can hear the hissing, then smoke is going to show nicely.
I have not. I'm going to try to make a soldering iron smoke tester to see what I can find.


1998 V70 GLT Black/Beige 193k
2000 V70R Venetian Red/Charcoal M56 Swapped 188k
2001 S60 2.4T Black/Black 230k
2007 XC90 V8 AWD Sport Titanium Grey/Black 155k
1998 S90- Silver/Gray 207k
1995 850 collection of parts... crushed... still have parts, PM if interested!
1988 744 Turbo M46 Beige Metallic/Beige 188k- Still kicking myself for getting rid of this one

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Re: Narrowing down a boost leak- 2000 V70R

Post by bmdubya1198 » Thu May 16, 2019 7:37 pm

Okay... did a smoke test today, discovered a small leak at the IAT sensor. Pushed that in the rest of the way, no more smoke coming out of anywhere on the intake manifold or ETM hose. Test drove it... absolutely no difference.
It's weird... in second gear, the car will work its way up to 14ish PSI, but 3rd-5th it absolutely will NOT pass 10 PSI, and sometimes it'll take a very long time for it to get there. In first if I'm not hammering it, it'll go back into vacuum even when I'm at 1/4-1/3 throttle. I definitely feel like there's a leak, but I just can't find it. I just think it's really weird that the boost behaves differently in each gear. Or maybe I'm just crazy or not being as consistent as I think I am with the throttle.

Anyway, I've got no idea where this leak could be. I can hear it when I'm on the throttle, but I can't find it when I pressurize or smoke test the intercooler piping. I just don't get how I'm not able to find this leak.


1998 V70 GLT Black/Beige 193k
2000 V70R Venetian Red/Charcoal M56 Swapped 188k
2001 S60 2.4T Black/Black 230k
2007 XC90 V8 AWD Sport Titanium Grey/Black 155k
1998 S90- Silver/Gray 207k
1995 850 collection of parts... crushed... still have parts, PM if interested!
1988 744 Turbo M46 Beige Metallic/Beige 188k- Still kicking myself for getting rid of this one

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Re: Narrowing down a boost leak- 2000 V70R

Post by abscate » Fri May 17, 2019 4:47 am

Unless you know the exact map of boost vs load ( not rpm) then you are hunting The unknown here. Maybe the tune guys know this?

I would disassemble the entire induction and inspect by flashlight for subtle splits


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Re: Narrowing down a boost leak- 2000 V70R

Post by DeadEric » Fri May 17, 2019 7:41 am

I have a low boost issue too so I've been doing a ton of research on how everything works. I'm gonna write some of it out in the hope that someone points out where I'm wrong.

Exhaust flow, impeller spins, boost pressure created.

TCV and waste gate.
Tube from the turbo goes to the turbo control valve. TCV then routes air to the watse gate and back to the intake. TCV regulates pressure (with ecu input) to the waste gate opening it when necessary to prevent over boosting the system. It does this by a "controlled leak" of pressure from the turbo to to the waste gate and leaks it back into the intake preturbo.

Bypass Valve.
You also have a bypass valve the opens when pressure is too high and bleeds off boost back into the intake, preturbo.

From my research.
Waste gate actuator failure leads to consistent over boosting. Bypass valve failure leads to consistent under boosting. Turbo control valve failure can be intermittent and do different things based on what the failure is. Everything is self contained and doesn't leak out of the system.


Assuming all of that is correct (please point out where I'm wrong, I'm still learning.) You feel like you have a vacuum leak but smoking doesn't reveal one. The low boost isn't consistent. I'm thinking you have a TCV issue.



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Re: Narrowing down a boost leak- 2000 V70R

Post by bmdubya1198 » Fri May 17, 2019 8:14 am

I've thought about just pulling the intake manifold and inspecting it carefully. I'll see if I can get the intake gasket locally, I might try to pull it this afternoon.
DeadEric wrote:
Fri May 17, 2019 7:41 am
I have a low boost issue too so I've been doing a ton of research on how everything works. I'm gonna write some of it out in the hope that someone points out where I'm wrong.

Exhaust flow, impeller spins, boost pressure created.

TCV and waste gate.
Tube from the turbo goes to the turbo control valve. TCV then routes air to the watse gate and back to the intake. TCV regulates pressure (with ecu input) to the waste gate opening it when necessary to prevent over boosting the system. It does this by a "controlled leak" of pressure from the turbo to to the waste gate and leaks it back into the intake preturbo.

Bypass Valve.
You also have a bypass valve the opens when pressure is too high and bleeds off boost back into the intake, preturbo.

From my research.
Waste gate actuator failure leads to consistent over boosting. Bypass valve failure leads to consistent under boosting. Turbo control valve failure can be intermittent and do different things based on what the failure is. Everything is self contained and doesn't leak out of the system.


Assuming all of that is correct (please point out where I'm wrong, I'm still learning.) You feel like you have a vacuum leak but smoking doesn't reveal one. The low boost isn't consistent. I'm thinking you have a TCV issue.
It all sounds right to me. I've been thinking that maybe the TCV is still the issue. I'm on my third TCV and I've noticed only minimal changes (a little more boost than the last TCV this time). I might swap that today and see what happens.


1998 V70 GLT Black/Beige 193k
2000 V70R Venetian Red/Charcoal M56 Swapped 188k
2001 S60 2.4T Black/Black 230k
2007 XC90 V8 AWD Sport Titanium Grey/Black 155k
1998 S90- Silver/Gray 207k
1995 850 collection of parts... crushed... still have parts, PM if interested!
1988 744 Turbo M46 Beige Metallic/Beige 188k- Still kicking myself for getting rid of this one

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Re: Narrowing down a boost leak- 2000 V70R

Post by Sommerfeldt » Fri May 17, 2019 8:21 am

DeadEric wrote:
Fri May 17, 2019 7:41 am
Bypass Valve.
You also have a bypass valve the opens when pressure is too high and bleeds off boost back into the intake, preturbo.
You seem to be correct on most of it, except this one, I think... the CBV should send pressure to the intake manifold, not the intake pipe pre turbo.

Whether it matters or not, is a separate issue, I guess. :)

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