HELP to much boost!!

[3.0Duster]

i have a 90ShelbyVNT that has a 2.5" exaust and a 16psi computer, i recently brought it to my machanic to have the exaust gasket done, he told me that all the vacuum lines were worn and broken so he replaced them all, but now my turbo just endlessly spools up, it usually just goes to about 16 and stops, now it just keeps going up and i stop it around 20 because i dont wana blow my motor, what could cause this, my mechanic is stupid and thinks that the blow off valve isnt working right and is suppose to release pressure at 16psi, any ideas as to what could cause this?, thanks

[TRRBOJEEP]

Sounds to me like the vacuum line on the wastegate actuator is not hooked up right, or may not be hooked up at all. That would be the first thing I would check.

[3.0Duster]

i thought vnts had no wastegate, just an actuator for the vanes

[sdac_guy]

I was having a similar problem on my Daytona VNT. I have a cal that goes to 14psi but overboost shutdown is turned off. It would boost to the limit of the turbo, seemingly without any control.

It was caused by cracked vacuum lines. A couple of them looked okay, but as soon as I touched them, they fell apart. I had 3 or 4 of the hard plastic lines that were bad, and two hoses that had hardened and cracked, including the 'S' shaped one that connects between the 4 way connector and the intake manifold.

Once I got them all fixed car runs fine with boost under control.

Barry

[DirectConnection]

I had the same exact issue with my VNT ES car. 14.2 psi cal (hehe Barry) with no overboost protection. One small crack in the line going to the actuator which kept getting bigger... until I could finally find it. 25psi+ and climbing... whoops! I forget which line it was at the actuator (there's 2) but I believe it was the one at the top port.

Probably more than just 1 line broken/hooked up wrong if this guy worked on it. Use the vacuum diagram under the hood to trace everything out. be very carefull as they are brittle and break REAL easy.