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Actually I believe I got that same gasket from the dealer years ago when I had a vf11 on my 1st SS. Opened up the holes like you did, and ran with it. Didn't have any leaking problems then.

That new gasket should be sealing, and since that's a vacuum side of the turbo, it doesn't need to hold any pressure. Can you elaborate what you mean by the boost gauge went from reading -20 to -6?

The auxiliary purge shouldn't affect engine idle vacuum. Where do you have your boost gauge hooked up to?

Honestly, if you still think that gasket is leaking, just get some generic gasket material and cut one out of the shape you need.

Have you checked your bypass valve to make sure it's holding under boost?

At idle the Prosport boost gauge normally reads -20 in/HG. I broke the aux purge valve nipple off and glued it back together. In it's place I installed a T fitting. The boost gauge then read -6 in/HG at idle. This morning I put it back on and the gauge was back at -20 in/HG. So it must have been the cause of the different idle vacuum.

I have the boost gauge connected with a T fitting next to the boost control solenoid.

All right, maybe the new gasket isn't leaking. So the boost leak must be on the pressurized side. There are no visible cracks in the TB intake (there were some in my old one and I replaced it). I'll go check the bypass valve right now. But I am not so sure I will be able to detect anything with my bicycle pump leak detector. Since the boost leak occurs usually around 3-5 psi I don't think my bike pump can build up enough pressure. At least it hasn't been able to do so yet. Tomorrow I'll make a fitting so I can hook it up to an air compressor and I'll borrow a friend's.

I do have another STi bypass valve that goes to my XT tmic.

Could the boost leak be a leaky exhaust manifold gasket by chance?

Back outside in the cold to see if I can detect anything...

I hooked the leak detector back up and pumped away. There is no more leakage at the turbo inlet gasket so I'll leave it alone. As I pressurized the system I found air leaking where the oil filler tube connects to the block, I don't think that is my boost leak. It also makes me a bit afraid to actually hook the system up to an air compressor. If the oil filler tube can leak maybe I could pop my cam seals off or something dangerous.

I also found a few very small leaks at my T fitting that connects to my boost gauge. I put zip ties on the connections and the leaks went away. I then found a small leak at the T that connects the aux purge valve to the pressure exchange solenoid and intake mani. I installed a new T. But I also don't think that is my boost leak.

BTW, I realized that my boost gauge is not T'ed to the boost control solenoid, but T'ed to the line that connects the pressure sensor to the pressure sensor solenoid. Should I T into the boost control solenoid instead?

I couldn't detect any leaks at the bypass valve. I sprayed the connections with soapy water and didn't see any bubbles.

I'm about ready to take it in somewhere to get an actual smoke test. But I'll hold off on that for a bit since the car is running fine otherwise. Maybe I'll just wait a while until I get my TD04 that my friend is supposed to send me.

At a loss at this point.

Here's my boost leak detector set up. All PCV connections are capped off as well as the two vacuum lines that connect to the resonator.

When doing the pressure testing I would open up the oil filler cap so you don't pressure up the crank case too much. You will get some blow by on the rings, but if it's substantial, you've got an internal issue.

How do you have your vacuum lines hooked up? None of the purge lines, main purge or aux purge should be hooked up to the line coming from the intake manifold going to the pressure exchange solenoid and ultimately the MAP sensor. Your boost gauge is the only thing that should be hooked up to this line.

What I meant by the bypass valve was internal leaking. Remove the valve and try to blow through it. You should not be able to. If you can, it's bad.

All of the vacuum lines are connected as they should be in their stock locations. Is that what you mean? I haven't altered any of their routes. Or do you mean how are they hooked up when I do the boost leak test?

During the leak test I just disconnected the two vacuum line going to resonator so I could remove it. Lines J & Q in the diagram below. I capped them off.



I'm a bit confused. Are you saying that I should cap lines C and H when I do a leak test? Thanks.

edit: About the bypass valve. Can I remove it from the tb intake without taking the tb intake off? The tb intake is stuck fast and I was having a really hard time trying to remove it the other day when replacing the turbo inlet gasket. It was very cold out and I felt like it was going to break if I forced it off. Do you have any tricks for getting it off? It's not a flexible piece by any means.

Also, am I OK tapping into the pressure sensor vacuum line for the boost gauge or is there another ideal location to tap into?

When it's really cold, or even warm at that, and you are having a hard time getting some of the hoses off or the intake pieces off, Use a heat gun on a low setting and just heat up the hoses or whatever else to warm them up to remove them. It will make the process much easier.

monkeyposeur wrote:
edit: About the bypass valve. Can I remove it from the tb intake without taking the tb intake off? The tb intake is stuck fast and I was having a really hard time trying to remove it the other day when replacing the turbo inlet gasket. It was very cold out and I felt like it was going to break if I forced it off. Do you have any tricks for getting it off? It's not a flexible piece by any means.

Also, am I OK tapping into the pressure sensor vacuum line for the boost gauge or is there another ideal location to tap into?

The hose that connects the BPV won't come off without a struggle, and are brittle. The charge pipe is a pain in the ass because it's not flexable at all, with mine I just stood at the front of the car and pushed it forwards and side to side. You gotta get it to slide off both places at the same time kinda, just gotta work at it. The BPV hose is held in by a clip on the back of the charge pipe.

Loosen the hose clamp on the return line, which is circled here



Then pull the charge pipe off if you can, maybe get the engine warm or use a heat gun, and then remove the BPV from the tb hose. The clip kept getting in my way so I just snapped it off because I didn't need it.

The vacuum line I use for my boost gauge would be the #1 runner or hose C on the diagram and I have had no issues tapping that line.

monkeyposeur wrote:All of the vacuum lines are connected as they should be in their stock locations. Is that what you mean? I haven't altered any of their routes. Or do you mean how are they hooked up when I do the boost leak test?

During the leak test I just disconnected the two vacuum line going to resonator so I could remove it. Lines J & Q in the diagram below. I capped them off.



I'm a bit confused. Are you saying that I should cap lines C and H when I do a leak test? Thanks.

edit: About the bypass valve. Can I remove it from the tb intake without taking the tb intake off? The tb intake is stuck fast and I was having a really hard time trying to remove it the other day when replacing the turbo inlet gasket. It was very cold out and I felt like it was going to break if I forced it off. Do you have any tricks for getting it off? It's not a flexible piece by any means.

Also, am I OK tapping into the pressure sensor vacuum line for the boost gauge or is there another ideal location to tap into?

I was asking because in looking at the picture you posted, some of the lines seemed to be connected strangely during the testing. It must have just been how the picture looked. If you have the lines hooked up in the stock configuration, you should be fine.

You're fine tapping into the pressure sensor vacuum line for the boost gauge.

I built this pressure tester for .32 cents, worth a try.

Nice!

martimus919 wrote:I built this pressure tester for .32 cents, worth a try.

What are the materials? I would love to make one to test my system. Can you post exactly how you made it?

I just went to Home Depot to find anything with a 3" diameter that I could drill a hole through and pop a valve in.

That piece is some kind of plug or cap I found in plumbing. To be honest I can't remember what it was called though.

In action...

I made one that was similar and have already used it a few times. Mine is a little more complicated but the same idea. My bike pump hose wouldn't reach to the turbo inlet elbow so I made a connection with a hose. I found one that was about 70 mm in diameter (2.75") to fit the 67 mm inside diameter of the turbo inlet.

I have used it twice and found a major leak in the turbo inlet gasket, but no other major boost leaks. I found a few tiny leaks in a few vacuum lines such as the t that goes to the aux purge valve, so I zip tied them on and they don't leak any more. This is why I am leaning towards thinking the BPV is bad, hopefully.

If anyone has a stock SS BPV let me know. I don't want to attempt to remove the one that is in place unless I have a working spare on hand. I don't want to risk breaking it during removal and being SOL.

Here is my boost leak tester:


In action:


Mine cost $10-15 and was also made from parts I found at Home Depot.

Here are the materials:


martimus: Did your system hold pressure for any length of time (mine wouldn't stay pressurized)? Also, did you take your oil filler cap off to do the test? I had air escaping where the oil filler neck connects to the block.

I found a stock SS BPV locally so as soon as I get it I can check mine and see if that is the problem. I am also getting the tb intake as well in case I break mine, lol.

Just another quick question: What are the usual symptoms for a faulty BPV? And is it not too uncommon for them to go bad?

I'm working out the details with picking up my replacement BPV but I was just wondering if anyone has any specific insight into this?

One of my bad BPV's made the turbo do a cool "turbo-flutter" sound, the other just had a vacuum gauge reading of 10inhg. When I replaced them the engine was more responsive, and vacuum was right under 20 inhg at idle, when warm.

As someone mentioned above, I was able to blow through the bpv without much/any resistance, which is bad.

I received my replacement BPV today. I'll install it this Saturday hopefully.

Questions: Is it possible that my MAF might be failing and causing the problem? I'll clean it with MAF cleaner as soon as I can.

EDIT: I was looking in the FSM parts catalog and the MAFs of the MT and the Turbo share the same part number (22680 AA170). Does anyone know if they are interchangeable before I go and search for one at the junkyard. I am sure that I could find a na MT MAF easily out here.

So long as you grab an aluminum AA170, you're good. If you can't find one, I have one.

I have one if you wanna save yourself the hassle. 50 shipped.

Thanks for the offers on the MAFs guys. But I came across a Touring Wagon at the scrapyard today and luckily it still had the MAF (no engine). I also took the bcs, aps, etc. off it for later.

Great news!!! I cleaned and installed the new MAF and the SS runs PERFECTLY! No misfire, or put put problem any more! It must have been the main issue all along. Even when I stomp on the gas WOT I no longer have any problems. The acceleration is unbelievable and it knocks you back into your seat. The VF-11 spools instantly and hits stock boost no problem with no hesitation whatsoever. Then when I engage "POWER" mode via my switch it really takes off.

I am thrilled beyond words. It has taken me almost a year to fix this problem and now I finally get to enjoy my stock 160ish hp! Thanks everyone that chimed in.

Now that I found the problem I can move on and install the TD04, tmic, and coffee can.

That is great news! Congrats!
Now you'll see what a money pit these cars are

Tell me about it! I just found a PNPed TD04 to install.

Glad you got it figured out and fixed.

Thanks Josh! I had no idea the car could perform so well. I gave the car back to my wife to test drive and she was screaming she was so happy! The power mode is awesome. If you go WOT if revs up to 5k before shifts. The nose of the car raises and you can feel so much torque it is mind blowing. I can't wait to see how the pnp TD04 and TMIC improve things. It's pretty quick off the line now.

It's a good thing the HGs went as soon as I bought it, and that it took me so long to diagnose the problems. I know so much more about how the engine works and I am a much better shade tree mechanic because of it all. This site is such a valuable resource.