Failing turbo? What should I listen out for?

[chrisgeary]

My VW garage tells me my turbo is noisy. Something is noisy when the engine is cold or has been stopped for half an hour or so. The engine sounds normal until it is revved. If it is revved gently, it still sounds normal. If it is revved with more throttle (not higher RPM) then there is a metallic tapping/knocking noise, quite hard and brittle sounding that raises in pitch with the throttle and frequency with RPM. Come off the throttle (but RPM stays the same) and the noise goes (audibly anyway). Its quite loud in the engine bay and its quite audible inside the car even with road noise at 30mph.

This lasts for about 1 minute of normal driving and then the engine sounds perfectly normal. No loss of power, the turbo provides boost normally. No fault codes.

Another mechanic says it might be hydralic tappets which haven't received enough oil yet.

Anyone familiar with the sort of sound I'm describing? If not, Ill try to record it.

Lastly, if a turbo is on its way out, how might it fail? Would I only notice a problem cold, or would it be evident under full throttle at operating temperature?

Thanks for your advice,

Chris

[Panzerdriver]

If a turbo is making a rattley noise then the bearings are shot game over new or overhauled unit required.

You will also notice a decrease in power, increased oil consumption (noticeable by large amounts of blow smoke coming from the exhaust)

Because of the high speeds that turbos operate at bearing failure will cause the impeller and turbine to rub in the housing which will result in the turbo making a increased whistling noise that will increase/decrease in relation to throttle loading. (Turbo will go bang) :cussing:

One way of checking is to get access to the impeller by disconnecting the inlet piping and see if there is any play plus you may also be able to see if there has been any housing contact.

If you use the seach facility on this forum you will find more info on turbos plus maybe other info on the noises your engine is making.

Sorry not good news but crasher maybe the man to ask as he is a guru with VW's

[chrisgeary]

No loss of power, in fact the performance is very good indeed. I should take it to a rolling road because it feels like it has more than 150hp sometimes.

No extra whistling noise, no smoke, no increased oil consumption. (Should I feel happier now?)

[caldirun]

No loss of power, in fact the performance is very good indeed. I should take it to a rolling road because it feels like it has more than 150hp sometimes.

No extra whistling noise, no smoke, no increased oil consumption. (Should I feel happier now?)
Turbos run at very high RPM, they dont knock or rattle, if they are knackered they scream, look elsewhere for you problem

[vivrow63]

could be the cat has broken that rattles and sounds like the turbo becuse it is just below,read my post.

[chrisgeary]

Here is an mp3 of the sound (http://www.christophergeary.co.uk/Passat.mp3).
The first rev up is slow and gentle, note no knocking.
The second rev up uses more throttle and the knocking is now apparent. Repeated 5 times then I hold the throttle at about 2500 RPM and the knocking goes away.

Anyone recognise the sound?

[vivrow63]

yes this sounds the same as when our cat failed, now the thing is they sell straight through pipes in the us that get rid of the cat and it appears they do produce more power without ours made this rattling sound just below the turbo and we had no power loss but the catalyst bounced around wore down into a round shape and blocked the exhaust reducing the power.

[martin1810]

Its's amazing the vw garage thought that a damaged turbo could make a knocking noise when you consider how fast it spins. Try sticking a long bar or screwdriver against your ear and touching the end onto the area where the sound seems to come from. This might help you narrow it down. KEEP WELL AWAY FROM MOVING PARTS.

[Sharkie]

Doesnt sound like the turbo to me sounds like the cat or tappits