Yd25 R51/D40 Air Surge noise

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Hendersk

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Hi there Guys, My first post so hello to everyone!

Big Nissan fan, technically I don't have a Nav, have an R51 2009 2.5D (240km) pathfinder, but arn't they basically a Nav from the B Pillar forward?....

If you include Terrano/Qx4/regulus then this is about my 5th Pathfinder and they have looked after me famously so far right through the engine range from 2.7t, QD32, ZD30 and now onto YD25.

Anyway the issue at hand that I would really appreciate the "Brain trust" assistance with.

Today the R51 started doing something very strange. A new sound popped up that has me puzzled! It sounds like a very loud surging or rush of air (large volume sound, not high pressure sound). First noticed it after driving and came to the lights etc then this big swoosh sounds winds up lasts 15 sec or so and fades away. Hot Day (30 ish)

Throughout today I tried many different driving modes, AC on, AC off Heavy for light foot, no connection. Fired up the OBD and checked temps and boost. Everything else seems fine apart from this (loud) noise. Later I noticed that at light throttle I could pick it out at time while driving also. When I could catch it surging, nothing I could do would stop it, it would simply run its course, tried revving engine, switching AC etc and the noise seemed unrelated. low PSI boost at the time of surge so its not turbo related.

One thing I did notice and it may be nothing, the inlet temperature would climb way above ambient (40deg) when the surging was going on and when it wasn't return to ambient - 28 so assume air must have been entering the intake?

As the AC pump seemed to be making a grinding noise when switch off I thought perhaps this was related, AC pump grind smoothed out when pump is loaded.

The only other thing, that seems to be a bit too coincidental is that this is my 2nd trip in the vehicle since blocking the EGR........ but doesn't that lower inlet temps!

Anyway I have searched the boards and the internet and I cannot find anything similar, perhaps this is a normal noise for a D40 / R51?

Oh and yeah, I pulled over and pulled the bonnet quick and caught it in the act once and it was hard to pinpoint..... seemed to be audible from the EGR right around the back of the motor to the intake.... but then it was hard to pinpoint....

My thoughts are
- Air lock in cooling system?
- Some EGR related fault
- Air Con defect causing surging in the AC lines
- Viscous Fan
- .......... out of ideas

Any and all help appreciated, not really sure who to get to look at it, get a cooling system service, or an Air con specialist? I know Ryde Nissan will just be guessing, they recently tried to charge me $4500 for a turbo gasket!!! but thats another story.....

Thanks and sorry for the essay!

Kane
 
Hey Thanks guys for the help thus far!

I have gotten to the bottom of it, though it became fairly apparent.

At first start this morning the sound arose again and at every lights on the way to work. Was a cold day and vehicle hardly got hot. Anyway with its progression the noise changed from an "Air noise" as I originally interpreted to more of a grinding mechanical type noise and I noticed that the AC switch did have an effect on the noise now, though present still in both on and off just with a different sound.

On the way home the noise disappeared all together even at the light..... when things fix themselves thats not usually a good sign right?

Anyway a few KMS later and there is a smell....... then followed by smoke..... pull over and the AC compressor pulley is smoking away like crazy, a dribble of spit and it can be seen to be sizzling hot!

Anyway I'm off the road now, luckily there is a mechanic a short drive from home, managed to limp back in a combination of short trips after cooling off. Wouldn't you now it though, got it to his place and started it up and the pump was spinning again! I am guessing due to the nature of its development it'll be a clutch issue, but maybe its a bearing, not sure at this stage.

Fingers crossed its not too expensive

Looks like the tie in with the EGR plating was purely co-incidental!
 

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