Negative / no boost pressure when hot

[greasemonkey]

Just wondering if anyone can offer idea's on a problem with the JX engine turbo boost.

I've had a boost gauge fitted and noticed for a while now that the boost pressure is fine when the engine is cold, boosts up to around 7-8 psi as expected under load, but once the engine is nice and hot, the boost drops off and can even start to read negative values.

At first I thought the gauge might be dodgy but put a second one on and it's confirmed the readings.

I've read this can be indicative of sticking vanes in the turbo which a clean out may sort out, but not sure if this would be the case.

Any idea's or suggestions on what to check, look for and cures - hoping it's not a sign the turbo's on the way out.
Cheers.

[lloydy]

I would say you would notice if you had no boost, it would be gutless.
Could it be the little hose between the manifold and gauge? It might be resting on part of the engine, getting hot and then collapsing?

[greasemonkey]

I made sure the hose is taped out of the way and not on the engine.

Saying that, now you mention it, I've used the supplied clear hose for the boost sensor, whereas the LDA hose I've T'eed from is the braided hose. Could the plastic hose be softening to a point it's simply expanding with the pressure?

I thought this was unlikely, but now wondering?

[busbuddy]

I've read this can be indicative of sticking vanes in the turbo which a clean out may sort out, but not sure if this would be the case.

dont think the jx has the moving vanes

also worth checking the boost hose to see if its split and opens up when it gets warm and soft

[greasemonkey]

Cheers for the info, definitely starting to sound like could be a hose then.

My concern is that if the sensor isn't getting pressure, the the LDA isn't either, so even if I have boost I'm not getting the fueling that I need, so will definitely need to check the hose to the LDA.