Hi folks my focus 2011 tdci has developed a problem when under acceleration above 3000 rpm the pipe from the air filter to turbo and the short pipe to crank case breather is collapsing .It brought the EML on the other day and overboost was the fault code.Actuator on turbo is moving manually and when car starts and switches off.

Any ideas would be welcome don't want to start throwing parts at it for the sake of it .

When I disconnect short pipe to crank breather and rev pipe doesn't collapse but it seems to breath back through turbo like the wastegate isn't working .

What condition is the Air Filter in ? when did you last replace it ?

Air filter is clean.Have a service kit to do this weekend .Removed the air filter and still have the problem..Air filter is back in .

11 hours ago, Andy Focus tdci said:

above 3000 rpm the pipe from the air filter to turbo and the short pipe to crank case breather is collapsing .It brought the EML on the other day and overboost was the fault code.

Very strange pair of symptoms. I assume you have seen it collapse while revving to 3000rpm in neutral. If so there has to be a blockage in the intake, maybe something is lodged in the pipes leading to the air filter. On the Mk2 these pipes include the ECU housing compartment, not sure if that applies to the Mk3 (assuming a 2011 car is Mk3).

A blocked intake should cause an underboost error, not overboost. A problem with the MAP sensor would be the only reasonable cause of that confusion that I can think of. If it read low pressure, it would wind the turbo right up, and give that error. Which engine is it?

But regardless of the turbo boost, only a blockage in the intake (or a very, very weak bit of pipe) would cause the collapse.

Yes it's collapsing when vehicle is stationary .

I replaced the alt drive belt and was checking the charging when I noticed it collapse.

Fault code was p0234 overboost 

1 hour ago, Andy Focus tdci said:

Yes it's collapsing when vehicle is stationary .

I replaced the alt drive belt and was checking the charging when I noticed it collapse.

Fault code was p0234 overboost 

Which engine do you have?  Both 1.6 & 2.0 TDCI in Mk3's have VNT turbo's, not wastegated ones.

I'm wondering if the VNT mech has broken internally so even though the actuator is moving, it's not physically opening the vanes.

Can't confirm engine code as I'm at work .I know it has the variable vane .I've priced a turbo for it and it's not as bad I thought.Im with you I'm convinced the variable part is faulty.

If I drive the car normally it boosts ok it's on on an agressive acceleration it's not happy .

 

So it turns out I had 2 separate issues within the turbo and intake system .

Fault 1 overboost ended up being the turbo itself ,the vanes weren't being very variable .

New turbo and a few oil changes since last Wednesday .

 

Fault 2 collapsing air filter to turbo hose.

Cheap hose was collapsing under higher revs.

Bit the bullet and bought another hose even though this was only 6 months old.

New pipe fitted and not collapsing.

 

Various vacuum tests were done to determine fault lay inside the turbo .

Connected hand held vacuum /pressure pump into vacuum system and started the vehicle,vacuum was good when I revvd the car slightly it went from a vacuum to zero reading....indicating all was fine to the turbo.Replaced turbo and you would be surprised at the difference in the cars performance.I just wonder how.long the turbo has gradually been declining in performance.

 

Most money I've spent on this focus but I've had it 7 years and it's the first but of drama she has caused me .

155k on the clock 

Few springs 

Disc and pads 

Clutch kit last year

Tyres 

Wheel bearings just the usual higher usage vehicle things .

 

Never failed to start 

I love this car .......

 

For now .

 

Thanks for everyone's input ,it was appreciated .