115 Tdi Sudden Loss Of Power

[isk]

Hi all,

My galaxy is a high mileage automatic so there's no surprise that it loses power on 4/5 gear when going uphill or simply while accelerating ...the exhaust manifold and the turbo must be heavily blocked by soot , but there's also a funny noise coming from the turbo area...what's surprising about it is seems to have a constant frequency (about twice a second) regardles of the revs - also the noise disappears completely when the power drops and goes into limp mode.

Now, I've tried to clean the turbo by applying the 10k booster - the first application did wonders, but only for a couple of days, then the dreaded limp mode returned - I since tried the ecoboost and 2 more cans of 10k boost but no improvement at all - I suspect they only work on the combustion chamber and first bit of exhaust manifold with dissolved soot beind dragged further down the manifold and effectivelly clogging the turbo even more. Then I resolved to tackle the soot from the exhaust side - the flexible pipe is easily removed (3 nuts 13mm socket) - I sprayed half a can of a paint stripper mousse into the turbo and then inserted a the nozzle of my steam cleaner into it for a couple of hours to soften the soot- after this the actuator rod on the turbo worked freely as never before! Again, this worked fine for a couple of days until the limp mode came back again - I think the dissolved soot still keeps coming from the exhaust manifold as I have some quantity of injector cleaner still in the tank.

I know the paint stripper option might seem foolhardy as this stuff dissolves rubber seals etc but I just hoped there was no exposed seals in the turbo as the exhaust gasses would have burnt them in no time..

Back to the noise, it sounds a bit like a worn bearing (which it is not) but it's the steady frequency of it that totally baffles me - it seems to sligtly affect power when it occurs - a fraction of a second slight hesitation twice a second or so - I hear and feel it at the same time

I have asked a few mechanics about the problem...no one had a slightest idea!

Obviously, I would be grateful if someone could point me in the right direction.

[isk]

I just thought that I should try and describe the sound a bit better... it's like grating between a rotating element and sometning... sometimes it causes the car to vibrate slightly

[makil6]

Not too sure, but it may be the bearings on the turbo on there way out causing the impeller to rub inside the turbo housing. I was having similar noises just before my turbo gave up altogether. When it did go, it had no power and loads of blue/ black smoke due to the oil thats meant to cool the seals passing straight out the turbo and into the exhaust. Hope im wrong cos it ended up a bit costly. Best of luck.

[f0ster]

Not too sure, but it may be the bearings on the turbo on there way out causing the impeller to rub inside the turbo housing. I was having similar noises just before my turbo gave up altogether. When it did go, it had no power and loads of blue/ black smoke due to the oil thats meant to cool the seals passing straight out the turbo and into the exhaust. Hope im wrong cos it ended up a bit costly. Best of luck.

 

remove the inlet pipe to the turbo, get hold of the turbo spindle with a pair of pointed pliers, see how much lift in the spindle there is, also check the end float

of the spindle, a turbo spindle will have slight lift, there is not usually any end float, also if the turbo had worn spindle bearings it would

very quickly stop giving power completely, you would not get it comming and going, also once the spindle bearings go the turbo usually

pours oil down the exhaust, if your has a diesel type cat fitted it might have blocked up,

[isk]

Thanks for your suggestions guys - I don't think it's the turbo bearings as I've driven this car for two years now (done 8k miles) and the noise has always been there - never got any better or worse.

As for the blocked cat - that's an interesting suggestion but why would it lead to this noise which has constant frequency regardless of the revs...

[seatkid]

If its like my "whistle" then...

 

Partly blocked EGR valve. Its a high pitched whistle (sort of old style TV whistle ~6-8kHz). Symptoms were - only did it when warm and is worst when constant speed/part load. Pitch (frequency) stayed the same only the volume changed with a tendency to appear or disappear abruptly.

 

I cured mine by using double dose of Millers Diesel Sport 4 and some sustained Italian tuneups (welly) over a couple of weeks. LOTS of black smoke during the Italian tune up. :)

 

You could always remove the EGR valve and clean it by hand. :D

Edited June 16, 2008 by seatkid

[isk]

well, it isn't really a whistle...its only about twice a second (is that 2Hz?) .Again, the EGR valve could well be blocked (145k miles after all!). Seatkid, how did you find out it was wat it was?

Also, when I open the bonnet the sound comes from the airfilter box area or below it...and it happens when engine's cold as well

[isk]

had the car at a local garage, they looked into it and assumed faulty turbo, which is weird coz' it's actually working fine with plenty of pull, also after 5 sessions with 'paint and gasket stripper' sprayed into the exhaust side of the turbo the actuator finally moves freely. Today I took the flexible pipe off and drove to check if the cat was to blame, but no difference, apart from the scratching noise becoming more a hissing noise. Even with the turbo seemingly cleaned it still tripped on me once - the VAG com readout as usual...positive deviation or something. I definitely notice a hesitation in power 2-3 times a second (it accompanies the noise) at low speeds which is quite surprising given the weight of the car. And I'm still baffled why the frequency of the noise stays almost the same through the gears and revs. Surely it must have happened to someone else...help!!!

[seatkid]

positive deviation means turbo overboost.

 

Could be

 

1. sticky variable vane actuator mechanism (it could be worn out)

 

2. sticky turbo control solenoid (TCS)

 

3. Loose vacuum connection, check the turbo control vacuum reservoir (IIRC tennis ball size sphere) in front of the engine block, one or two have reported a loose fitting bung...

 

4. check the small pipe to the back of the air filter box, this is the "atmosphere" connection to the TCS, check its not blocked and the air box connection is clear.

 

5. It may pay to check your main air pipework e.g. clips at the intercooler etc.

 

From your description sounds like the ECU is struggling to keep the boost constant (oscillating between too much and too little, eventually tripping on an overshoot)

[isk]

thanks seatkid, I think you're right - the guys at the garage said that the actuator arm moved in somehow erratic way - what would it point to in your opinion? does it explain that strange sound? is a new turbo required? how would I check the N75 solenoid ?

[f0ster]

thanks seatkid, I think you're right - the guys at the garage said that the actuator arm moved in somehow erratic way - what would it point to in your opinion? does it explain that strange sound? is a new turbo required? how would I check the N75 solenoid ?

 

I would replace all of the vac pipes that are connected with the boost control, they gey oil in them and prevent

smooth operation of the boost control via the n75 valve,