Engine: D5: Intermittent boost problem seems to have become permanent!

[TonyGK]

So please help, I have the intermittent problem what is it that causes the Turbo not to work now and again? Turbo boost valve and a lot of other stuff already replaced?

[Simmy]

splits in vac hoses or sticking turbo vanes

[Suttv70]

Originally Posted by Simmy

splits in vac hoses or sticking turbo vanes

It was a piece of intercooler flexi host that had escaped the jubilee clip. I lost boost under certain circumstances/ it was fine at other times.
I easily spotted it because it was visible looking down at the pipe but if it had been underneath it wouldn't have been visible as the undertray obscures the view from below and I wouldn't have easily spotted it.

Now being a Volvo owner of some 3 weeks experience, turbo/intake leaks would be the first thing I would check for your symptoms.

The metallic grinding sound on startup and shutdown I would be suspecting some intake swirl mechanism or variable intake which I know from a mk1 Focus ST that I own that suffers such issues. But actually, as Simmy says, turbo could be a suspect and my 150K D3 (same engine but lesser capacity) has had a new turbo in its life before my ownership. If you think about it, the turbo spins up from standstill and slows to a standstill on startup and shutdown so that's when you might hear grinding but when it's spinning with oil pressure in the bearings it might run quieter? I've seen people checking the turbo for excess play by wiggling the turbine but on the Volvo it isn't very accessible being down behind the engine, unlike my BMW diesel where it was sitting at the side facing the front and easily accessed.

[camturbo]

I believe there is a boost sensor on one of the intercooler outlets, close to intercooler also I think you may have the electronic turbo actuator which do and can fail as mine did. Could also be sticking turbo vanes.. mine is 07 v70 185. I undid turbo actuator from the turbo held on by circlip to see if vanes were sticking,they were free. Took off actuator took it apart and was no good. These cars can lead you a merry dance and expensive parts that dont need replacing if your guessing. You really need to get the codes read properly to get better idea of the problem. I assume you have the euro4

[BenPS]

Originally Posted by TonyGK

So please help, I have the intermittent problem what is it that causes the Turbo not to work now and again? Turbo boost valve and a lot of other stuff already replaced?

It was the EGR valve for me in the end. Volvo wanted something like £700. I took a gamble and got one from a breakers, and fitted it myself, for about £100. Worked a treat.