Narrowing down a boost leak- 2000 V70R

Post by **bmdubya1198** » 13 May 2019, 11:34

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?

Post by **abscate** » 13 May 2019, 11:46

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

Mine epically failed under boost

Post by **bmdubya1198** » 13 May 2019, 12:45

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

Post by **abscate** » 13 May 2019, 13:03

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

Post by **bmdubya1198** » 13 May 2019, 19:03

abscate wrote: 13 May 2019, 13:03 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.

Post by **bmdubya1198** » 16 May 2019, 19:37

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.

Post by **abscate** » 17 May 2019, 04:47

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

Post by **DeadEric** » 17 May 2019, 07:41

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.

Post by **bmdubya1198** » 17 May 2019, 08:14

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: 17 May 2019, 07:41 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.

Sommerfeldt · Post by **Sommerfeldt** » 17 May 2019, 08:21

DeadEric wrote: 17 May 2019, 07:41 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.

- S