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-   -   740: Why do I have a Saab valve on my car? And/or is this why I have no power under boost? (https://forums.turbobricks.com/showthread.php?t=279811)

doucheNozzle 10-17-2013 10:00 AM


Originally Posted by AdmiralSenn (Post 4716163)
Nope, no EGR.

You can get the sensor out without pulling the intake then.

AdmiralSenn 10-17-2013 03:50 PM

On a B234F intake? It doesn't look possible. I was planning to pick up a set of metric crows-foot and a set of metric stubby wrenches to try it, but it sure looks like I won't be able to apply any torque to it to get the old one out.

I'll give it a shot. Might even head to the store tonight and try it tomorrow.

doucheNozzle 10-17-2013 06:54 PM

Wait. It's a B234F intake? No idea how I missed that from the OP.
Anyway. You can get a deep socket on there and an extension.

AdmiralSenn 10-17-2013 07:32 PM

I dunno. Probably because the DOHC part of the car is the only thing on it that currently works correctly.

Also, you can fit a socket on it? I thought from the FAQ that you can't fit it over the sensor plug?


Holy crap, you totally can. I've been lied to! Looks like tomorrow morning I get to see if I can wrangle the socket in there and get some answers.

AdmiralSenn 10-19-2013 05:44 PM

It turns out that I should not trust my memory when it comes to procedures. Reading and looking at the motor helps. That was the easiest job I've ever done on the car.

ECT sensor replaced. Butt dyno says the car is incrementally better, although traffic is so bad I can't find an empty stretch of road to see how much better. It does seem to be more consistent between cold and warm, although I still lose a lot of power.

I also did adjust the wastegate down to where it takes just a teeny bit of extension to get it on the wastegate arm.

Also re-did my leak test. The air is still going somewhere, and it's either the turbo or my brand new silicone air fittings, which are clamped to the turbo using new T-bolt clamps and an electric impact driver. No splits or leaks there. I'm thinking that seal behind the compressor housing is probably bad as Janspeed suggested. I am putting a bit of strain on one of my hose joins, so a new one with a bend in it is on the way, but I expect the leak is actually in the turbo somewhere - it sounds like it's in a big cavernous space. This seems like a likely candidate. Probably won't get to inspect it unless I run across a decent condition T3 of equal or better performance that I can afford. I really can't risk trying to rebuild the turbo on a time crunch since this is my daily driver for the foreseeable future.

Bensin 10-20-2013 02:14 PM


The compressor housing has a rubber seal or gasket between backingplate and snailhousing. If that leaks you also lose boost.
It's all in the details.
I don't follow this description because it seems that any rubber attached to the housing is going to melt. What is "backingplate" or "snailhousing"?

Maybe your leak test is pointing to CBV/BOV again? Is the turbo housing cracked?

What are the symptoms now since ECT replaced?

AdmiralSenn 10-20-2013 02:36 PM

CBV is not leaking. Wastegate actuator is holding pressure as well. I also tested the entire pipe system from the intercooler to the pipe out of the compressor, which holds pressure all day long, and I tested going the other way (intercooler to throttle body) which also holds.

The leak is somewhere between the AMM -> turbo hose (brand new silicone) and the compressor outlet (also attached to brand new silicone). Basically it's as close to testing just the turbo housing itself as is possible. Here's the setup:

Line from compressor -> inflation attachment -> 'test cap' plug replacing AMM -> silicone elbow -> turbo inlet -> turbo outlet -> silicone joiner -> solid test plug.

I ditched the original cobbled-together hoses and everything from the turbo to the intercooler is new aluminum hard pipes with silicone joiners and adapters.

I don't see any cracks on the housing but I'm leaning towards something of that nature. I also can't easily check underneath because a friend has my jackstands and ramps.

Symptoms now are nearly perfect driveability, minus boost power when hot. I can stomp on the gas pedal and get no more backfires or struggling. Boost comes on hard when dead cold, then rapidly falls off as the engine warms. Boost gauge still shows pressure and responds to MBC adjustments but the power, while better than before, is still not up to par. Occasionally I will get a pull that feels like about 50% boost but I haven't found anything to explain why. When this happens, the 'felt' acceleration doesn't kick in until much later than usual.

All things point to something that gets worse with heat (e.g. cracked housing), and I can hear air whooshing through SOMETHING on the turbo when I leak test it, but I can't feel any air leaks. I wet my hand and ran it all around the compressor housing, but I can't feel anything. Previously I confirmed a leak this way when I could feel the air escaping from the wastegate actuator.

I'm wondering if it's possible for the turbo to be leaking internally somehow, but I don't have the faintest idea where it could be leaking. The shaft exhibits almost no play on either axis, it's like it's brand new.

The only other thing I can think of is that the silicone fitting on the outlet is supposed to be straight, but it's bent a little for clearance. I feel no leaks there, though, and the clamp on it is very tight. I've ordered a new 30 degree one just to be sure (also will help line up the piping a bit better) but I don't think that's it. I hope I'm wrong, of course.

AdmiralSenn 10-23-2013 12:37 PM

Man, I have got to have a word with the guy who works on my car.... (I am occasionally an idiot. Only on days ending with "y".)

I utterly failed to tighten a hose clamp last time. Still doesn't fix the leak in the turbo area, but adding MORE leaks isn't helping! Tightened it down, reset the ECU (since I put in the new sensor I figured I might as well), drove for ~50 miles so far. I now have boost consistently across the entire gamut of engine conditions, even at 80mph I have some extra power. Still only about 75% of what I had when it was new, but it's definitely better!

New hose elbow should be here today and we'll see if that makes any difference.

Also, I am smelling gas occasionally, but I can't find any leaks anywhere. I'm quite alarmed about this, since the last time a car did this to me it burst into flames. I'm thinking the FPR leaking internally, the new fuel filter is dry as a bone and I don't see or feel any dampness anywhere on the motor. Probably not helping the situation.

Man my car is a basket case. I sure know how to pick 'em.

Bensin 10-23-2013 09:02 PM

Loose hose fix! Can happen to anyone, glad it's fixed. I just realized you have a 16v, that's a smaller club than 8v, but there are crossover problems...

See this page, if you haven't already, and look under "engine tune and performance: symptoms" http://40mph.com/Brickboard_700-900_...Index_Version/

AdmiralSenn 10-24-2013 03:35 PM

Oh it gets better. I put the new 45 degree elbow in and 1) the intake pipes are now pointed nicely at each other instead of being coerced into fitting 2) there's a noticeable improvement on the boost front! For once I was right!

But that didn't stop me from leaving one of the clamps on the CBV untightened, and so my joy was short lived as it removed itself from the intake plumbing with a surprisingly loud PSSSHHT. I think I might be too stupid to own a car.

Nothing's damaged but my already flattened ego, though, and the car is quite close to the speed where I bought it. I think it might be a little quicker today because of the sudden temperature drop as well, but I did a decent length run and still had full boost when it was warmed up.

So it looks like the original major problem was a leaky/ruptured wastegate actuator, compounded by a poorly plumbed CBV, then made even worse with a bad fuel filter which then ruined the plugs, made slightly worse with a marginal ECT, and made impossible to diagnose by my attempts to fix boost leaks which really just added even more leaks.

Kids, this is why we do stage 0 before we go fast, mmkay?

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