doabarrelroll

After taking the car out yesterday, something happened where I lost all positive pressure in the system. The vacuum is good, but, anytime I try to build boost, it won't reach positive pressure. The engine itself appears to run fine, just missing the power of the turbo.

I pulled the turbo today and found black soot around two of the three studs at the bottom of the downpipe and on my exhaust. I'll also note that I could hear the turbo spooling MUCH louder yet still not developing pressure.

The turbo itself has little to no shaft play and both wheels are undamaged. It spins as it should as well.

My wastegate seems to be ok after inspection. How hard should it be to push on the spring? If anything, it failed in the closed position (Tial 38mm).

I've got the whole top end of the car off right now, so, any ideas as to where I should start other than replacing the downpipe gasket?

jb-kix

Look at th rubber hose fittings on your boost tubes ,a little split did the same on my car.

fwb42

Cracked J boot.

doabarrelroll

I found one split on a vacuum hose connected to the intake manifold, but, I'm not positive if it happened during removal. My J boot is original, so, I'll double check it for cracks.

Paulyy

how would the J-Boot be the issue of no boost?

Did you check your boost pipes? i forgot to tighten mine once and wouldn't boost properly back when i had stock rubbers.

doabarrelroll

All the IC rubber was replaced and was tightened down well as far as I remember.

Darud35

Have you checked your bypass valve? I believe they have a tendency to go out. If you blow into the + pressure side it should hold pressure.

Paulyy

could you open the wastegate with your finger? or does it feel like it's stuck when you try push the valve?

apply some pressure to it and see when it opens. if the spring is 7psi it should open around 7 psi. if it opens with any pressure under 7 like 2 psi for example, there's something wrong with the wastegate.

If it's louder and the turbo looks fine, i really think there was a boost leak, as the turbo is spooling but not making pressure, forcing it to spin faster.. which is bad for the turbo.

doabarrelroll

Ok, I couldn't open the wastegate with my finger. I guess I can still have good vacuum and a boost leak at the same time.

Bypass valve is good and holds pressure.

lart951

Bypass would not cause a no boost situation, but a leak on the exhaust a faulty wastegate or a collapsed down or crossover pipe wil l cause the non boost thing, now Kris did you really oppened the engine to check for the no boost issue?

doabarrelroll

I went out driving and heard a loud BANG and lost boost, so, needless to say I was a bit concerned by turbo had blown up.

racerxrick

hmm...last time that happened to me I blew an intercooler hose off (on the side of a busy highway). If I recall though the car went into some sort of limp mode (idle only).

Since you already pulled the top end and turbo off it may be difficult to determine what caused the loss I would think?

White_951

Same thing here....are you sure the connections were sound before you pulled the intake???

My recurring prob was the hard pipe to throttle body connection, not always easily seen.... and the swishing noise made by the loss of the connection was very audible....

Also, the big bang was probably your overboost protection, which seemed to always accompany blowing my hard pipe connection off....

968tcab

had the same recently, under wot in 3rd to 4th, bam, car shut off,mechanical vibration in shifter etc. Car started fine, drove fine, would not go into positive pressure, crawled under the car, two of my inlet pipe bolts to the wastegate were missing, the triagle flange was hanging on by one 10 mm bolt! Bought the 6mm bolt and nut and tightened it down, the whole exhaust tightened up as soon as it was cinched up. Boost was back up to 15 pds, but I still have the exhaust rattle from the heat sheild, the welds are broken off so the shield vibrates when I get on boost etc.
hope this helps,
Mike
968 turbo cab

doabarrelroll

Interesting stuff. I used to have that problem with the hard pipe to throttle body connection. I ended having the wash the silicone coupler like crazy so it didn't have any oil left on it. There is a very particular way it clamps on to the throttle body.