I bought back my old mk5 GTI

[JH86]

Boost pressure valve as in diverter valve?

Incorrect fitting/no O ring or a faulty valve?

Luckily yours is a KO4 car so easy to get at, I'd suggest crimping the hose over the cambelt cover from the compressor to the valve crimp it flat and see if power returns, ruling out any leakage first

Easy to do, won't cause any damage etc

Personally I'm a fan of the valve being binned

 

[Chris tii]

Boost pressure valve as in diverter valve?

Incorrect fitting/no O ring or a faulty valve?

Luckily yours is a KO4 car so easy to get at, I'd suggest crimping the hose over the cambelt cover from the compressor to the valve crimp it flat and see if power returns, ruling out any leakage first

Easy to do, won't cause any damage etc

Personally I'm a fan of the valve being binned

Not the diverter valve. One of these.

 

[gpaevo]

Not the diverter valve. One of these.

View attachment 438191

That's the same valve that failed on my vRS and caused it to over boost to 2.0 bar. I'd a boost gauge in the car after it was mapped so noticed it straight away.

Not that I needed the boost gauge to tell, as the car went like a rocket . Valve changed and back down to 1.25 bar.

 

[Chris tii]

That's the same valve that failed on my vRS and caused it to over boost to 2.0 bar. I'd a boost gauge in the car after it was mapped so noticed it straight away.

Not that I needed the boost gauge to tell, as the car went like a rocket . Valve changed and back down to 1.25 bar.

So mine maybe has been over boosting? I need a dyno.

 

[_Mackers_]

Boost pressure valve as in diverter valve?

Incorrect fitting/no O ring or a faulty valve?

Luckily yours is a KO4 car so easy to get at, I'd suggest crimping the hose over the cambelt cover from the compressor to the valve crimp it flat and see if power returns, ruling out any leakage first

Easy to do, won't cause any damage etc

Personally I'm a fan of the valve being binned

As above the diverter valve depending on what version you have are known to give trouble on these. "Rev G" is the diaphragm type which can split, "Rev D" is the piston type which are known leak in general. People on the facebook pages will fight to the death over which one is best.

Personally I changed to a GFB DV+ valve on my Cupra and never had an issue with it again. Could be worth looking into.

 

[gpaevo]

So mine maybe has been over boosting? I need a dyno.

Just get an analogue boost gauge and T it off a vacuum line, you'll see what it's boosting to.

 

[Chris tii]

Just get an analogue boost gauge and T it off a vacuum line, you'll see what it's boosting to.

I’ll wait and see happens Tuesday when it’s at BTS, because I’ll only make things worse if I start playing about.

 

[Chris tii]

The missing horses have been found and returned to the stable!

The boost solenoid valve thing was fitted upside down.

Chris at BTS spotted it right away. He then plugged in the ECU to double check that all the readings match the initial map log from Decimal Tenths.

The Golf is officially a maniac again.