D40 odd noise

Hi all,

I know this isn't much to go on, but thought I'd see if anyone can help.

My D40 has started making an odd noise in the last couple of weeks. The best I can describe it as is similar to the noise a power saw makes as you cut timber. It seems to be a bit intermittent and sometimes happens under acceleration, other times just as I come off throttle. It only lasts a second or so, which makes tracking it down a bit hard.

Any ideas where I can start looking?

Sounds like a boost leak to me. Look around the hoses between your turbocharger and intercooler - and between your intercooler and intake manifold. You're looking for black oil stains - a sure sign of a boost leak.

Also check the EGR tube (the gold tube that runs around the front of the motor). It's been known to crack.

Last, check the interface between the turbocharger and the exhaust manifold. The bolts should be tight and there should be NO black powder around the join. If there is, the turbo's come loose and the gasket may be acting like a reed in a woodwind instrument.

Thanks tony.

After a bit more playing around in the shed, I can replicate the noise by revving the engine up to 2000ish and letting it fall back to idle. It squeals just before getting down to idle.

I had a bit of a look from underneath and it looks like the rear of the turbo is a bit black with oil stain. Is this the exhaust manifold gasket you mentioned?

The turbocharger has two halves, if you like. One's silver, the other brown. The silver side is the compressed air intake side - inside is an impeller, that sucks air in and pumps it out the rubber hose up the side. The brown side is the exhaust - or driving side. Inside is a turbine, that is spun by the hot, fast-flowing exhaust gas.

The exhaust gasket is on that brown side. It will have a black DUST near it. It will look like dust.

If you see what appears to be black texta marks on top of the silver side, it's probably the hose that connects from the turbocharger to the baffle which is a small silver round thing attached to the side of the motor. It's right near the label "turbocharged air" in the picture in my garage.

If it's black oil dripping off the bottom, then you may have a seal leak. Oil (and coolant) flows through the turbocharger in order to lubricate and cool it. If either are visibly leaking, you have a problem and the turbocharger really needs to come out for a service. Be prepared to get some new studs for the turbocharger mount, I had a siezed one in mine.

As for your symptoms - they could also be a failing bearing in the turbo. It happens - usually because the engine is shut down a little too early after a hard run, the turbo is hot and because the engine stops, the oil stops flowing through the bearings, allowing the hot turbo to cook the oil. It forms a hard varnish on its surface and begins destroying the bearing surface. After that, it's fairly inevitable that the turbocharger will start to make odd noises, then wobble and screech, then go

BANG​

leaving small chunks of turbocharger to fly rapidly towards the intercooler. And that device, if it does nothing else in its life, will protect your engine from swallowing those bits, so you lose a $1400 turbocharger but save $10,000+ in engine repairs.

I hope it's not bearings. The simplest thing to check is boost leak, followed by exhaust gasket, then it gets harder.

To inspect the turbocharger (cold engine only!), you have to remove the air hose from the front and, with VERY clean hands, try spinning the impeller. It has to turn smoothly, if a little reluctantly from the oil in the sleeve. It should spin without any gritty feel and come to a stop fairly quickly. The shaft should NOT wobble at all. It MUST be tight. If it wobbles, the impeller could make contact with the housing and at 100,000rpm that's going to get really ugly really fast.

Let's hope it's a boost leak.

Thanks for the detailed info Tony.

Took some of the heat shields from around the turbo off to have a better look. Definitely oil from the bottom of the silver section.

Sounds like you've had your turbo serviced - what's involved? Do I need to cut out a kidney?

I blew the gasket between the turbo and the exhaust manifold, which started acting like a reed and made all sorts of strange noises. It just couldn't hold a candle to Gerald Albright, so I had it fixed.

The oil from there might be a worry. Now it's time to try and trace where that oil is coming from - is it coming from the centre of the turbocharger, or is it leaking out of the air hosing and dribbling down?

If it's coming from the air hosing, it's only a matter of fixing the clamps or finding the split and dealing with that. Might cost you a charge air hose.

There are two possibilities with the other leak: either it's the oil feed/return which might be remedied with a replacement rubber seal, or it could be the main seals of the turbocharger and that would require a turbo rebuild.

The rebuild kits aren't expensive. Here's one on eBay for a VW - same model number of turbocharger. Just under $30. Your turbocharger should be a Garrett 2056V - have a look around and see what you can find.

I think your kidneys are safe!

Alright, so I've got a (bad) video of the noise. You can hear it right at the end of the clip. It's getting more and more frequent so I've gotta do something about it soon.

http://youtu.be/5-9i60GPryU

What year model is it ? Auto or manual ? Have you seen a black sooty residue on firewall behind exhaust manifold or on cylinder head where the manifold bolts on ? Does the noise go away when engine warms up ? I have a 2013 D40 auto that has a very distinct short turbo whistle on deceleration , been there since day one .

Thanks for all the replies. Between this issue, the clutch, an oil leak and now some intermittent starting problem, I've decided to trade the Navara in on a run out PC Challenger. Pick it up next weekend.

210,000 reliable kms, but the issues are stating to pile up now. 5 years warranty and the price was too good to say no.

Good luck with the new car, hope it serves you well. One downside to the Challenger - you can smell everything in the cargo area while you're driving!