Nissan ZD30 problem from today has me stumped...

[Shannow]

had a trip of a couple hundred km today to meet my Mum...didn't make it, turned back with some issues.

Heading up a hill, the ute started a big "whooshing" noise, like an electric blower effect. Turbo wistle increased markedly also...Son in the back seat remarked "what was that".

Stopped and started troubleshooting to see if the trip was viable, or should be abandoned, given rubbish weather at the moment.

Found that the hoses connecting the turbo to a distance piece, and onto the manifold were a little loose, and there was clear evidence of an oil mist (crankcase breather fumes) covering the top of the cam cover, and having made it's way to the brake booster...wasn't there last OCI, nor there 3-4 weeks ago when I showed daughter how to check the oil and fluids on that one.

Tightened them up, and some of the wooshing noise was gone, but the turbo whined similarly...abandoned the trip and came home.

Partially blocked the air intake (hmmm, not the best idle, it broke the screen of the snorkel - can be fixed), but while the induction system was under vacuum, ether didn't change RPM at all...top hose connector was pretty squishy, so I replaced it on spec.

While the pieces were off, I started it, and the turbo provides at idle about a hair drier's worth of volume/pressure, so really not sure at all that I had vacuum in the intake.

Checked the EGR plate that I made and fitted all there and intake, gasket good.

While messing, I pulled the "throttle body" (it contains the shut off butterfly and the EGR/Swirl butterfly on these). Gasket good. the low swirl intake port was perfect (small oil film), the high swirl/EGR port lined with black "grease", that was quite thick, and smeared well on finger...residual carbon from EGR days.

Pulled the intake to the turbo, and the turbo (149,800km) was very tight, no end or radial play felt.

Pulled the heat shields off half of the exhaust manifold to have a look see. Interwebs indicate that an exhaust leak creates the whoosh, AND increased turbo whine...the shield that you can get off is over 3/4 exhaust runners, and is the usual failure point - 1 and 2 require the turbo off just to look-see.

No signs of failed gaskets on where I could see, but I doubt that a half hour and 25 miles is enough to make a noticeable stain as yet.

Thinking that having gone right over the air side, I'll leave the shields off and see if a carbon stain develops.

So...any ideas ?

 

[Silk]

Check the vacuum hoses on the wastegate, and the linkage to see if it hasn't dropped off, or seized. Have you got a loss of power ? Drop the front pipe, if you have a cat it might be breaking up. Do you have an intercooler? Feel the hoses to see if they expand when it should be boosting (big stab on the throttle and let it rev.) Vacuum opperated EGR valves make them make funny noises, but you've bypassed that. I reckon it was just the loose hoses....

 

[Shannow]

Thanks Silk,
wastegate looks fine, and isn't siezed...linkage is all there. Mrs holding the throttle down in neutral, and me actuating the wastegate with a shifter you can hear the turbo rise and fall.

Have read conflicting reports that you can get it to cycle with revs in neutral...Mrs not one for a big throttle stab while I'm watching, so didn't observe it move.

Next steps were planned on injecting air (regulated) into wastegate pipe when it's dry enough outdoors.
And was thinking about dropping that barrel front pipe for a look see as well...need a dry day for that too.

Pretty confident today that I don't have a grenade on my hand.

Thanks again.

 

[Silk]

I think you'll be ok there. A hose leak can make a real bad noise under boost. Had one of those in a few weeks ago, guys travelling past - huge noise and oil everywhere, SMOKE!!!! It had blown an intercooler hose off, put it back on, cleared the smoke and it seemed to settle down. I don't know why, someone had been there before me and double clipped the hose, and don't know where the oil came from, it seemed a bit much from the breather. Anyway, they went away and never came back.

 

[Jetronic]

oil tends to collect in lower intake hoses, I regularly can remove a sizeable amount of oil from intake pipes and intercoolers.

I agree with the hose leak being most likely. the turbo would have to spin a lot harder just to maintain boost, and this will be heard.

another option is the bypass valve (if a wastegate turbo) wasn't quite closed so you'd get exhaust going through the narrow gap at high speed. If a VNT, the nozzles could've been slightly stuck (rust/soot) and you create extra high exhaust gas speed past the nozzles.


Do you still get the noise now?

 

[Shannow]

Drove to work this morning.

Turbo is definitely louder, can hear it spool and run down, and 100km on over-run can here it slow down to a bit like an APU on a jet plant.

The woosh is gone, hoses definitely fixed that...now there's a "hiss" that seems to come in about the point where the turbo speed constants out, assuming it's around wastegate operation.

Hypotheses is that air leaks needed more power to make boost, bumped pressure up in the exhaust (wastegate closed to get more boost), and some tinny little gasket has parted ways.

Power is all there, just turbo noise, and that hiss...sounds a bit like that hiss that older automotive A/C systems make the first time that they take cycle in the morning.

 

[mk378]

You can hear that hissing from big trucks that had a stone make a hole in their intercooler (it's the first part on front). Air leaks like that lose a little bit of boost power but it's not going to blow anything up.