2011 d40 odd noise at idle

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51oul

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hi all, just a question. hearing some strange noises coming from the engine area lately. it's very sporadic when it happens. the noise is a whirring noise that increases and decreases if that makes sense... I have an audio file available if someone can tell me how to share it? sometimes it's there other times its not. when it is there it's only for a for a short while (30 seconds max) until it fades and disappears. I've recently had all the belts replaced and hasn't fixed the issue. turning the AC off doesn't change either. The noise happens with or without the AC operating. just wondering if anyone has come across this in the past? cheers
 
Things that whirr in the engine bay (apart from the obvious):

* Damaged blades on radiator fan. Look at the root of the blade for cracking. This is extremely dangerous as it could cause the blade(s) to start nicking away at the radiator.

* Thermal fan cutting in. There's a small electric fan down at the bottom right hand side of the radiator (the car's right hand side). It usually only cuts in when the coolant temp is at 105C or the aircon compressor is on.

* Turbo flutter. Generally it shouldn't. Have someone take a poke at your impeller. If the shaft wobbles more than a tiny amount, your turbo might be ready to pack it in. Please don't talk to me about turbo woes, my car is now on its third.

* EGR leak. Usually they break around the base of the gold pipe where it joins the exhaust manifold but it could be a gasket around the other side on the back of the EGR valve. If memory serves, the 2011 D40s had a flow sensor, so blanking the EGR completely will probably trigger a Check Engine Light.

* Idler pulley. It's located towards the right hand side and below the alternator. There's a cap over the front so you can't spritz the bearing directly but it would pay to give it a squirt under the cap with the fine tube on a can of silicone lube.

* Alternator pulley. Again, happened to me (must be lucky). The pulley broke off the shaft and the only thing holding mine in place was the tension of the serpentine belt. Alternator was replaced, problem solved. I don't think the 2011 had a "smart" alternator, it should be similar to mine.

* Exhaust manifold < - > turbocharger interface. Mine came loose (told you, I'm lucky) and was just loose enough to make the gasket sound like a reed instrument (you know, saxophone/clarinet etc but without ANY of the skill needed to do a decent job). Sometimes it would flutter, other times it would shriek.

Hope that helps.
 
thanks for the detailed advice Tony, i was thinking last night I'll get a video recording so I can upload that. just waiting for it to happen again now. I have a blanking plate in the EGR, i think it's the 550s that throw the error code. 2.5s seem to be all good with those. alternator has recently been replaced after the 3rd one we got one that worked that was working. that was a nightmare. I do recall my mechanics mentioning a few of my pulleys were a bit warped if that makes sense? anyway I'll chuck up a video when I can get.one. only real way to hear the noise over the engine noise is in the cab with (best heard in the drivers foot well)
 
https://youtu.be/Zcf1daTcamY

hi guys. here is a video I managed to record with the engine noise going in the background. you will hear the noise start to speed up to a constant whir towards the end of the video. the car is parked in carport in park. this was recorded from the drivers foot well.

I also looked at my radiator fan. cant see any damage to the fins etc. can't seem to find the thermal fan unless it's under a shroud or something. bit of gunk around the drivers side of the EGR pipe where I've blanked it but no damage to pipe. assuming the gunk is just leakage because I never put any gasket glue on when I put the block in (will do that tho). haven't looked at the other items pointed out by Tony yet.. any other advice is much appreciated
 
hi Tony, by dri lube do you mean spray a bit into the idler pulley assembly as you suggested above? the belts have recently been replaced (less than 2000kms ago) and the noise was occuring before then also
 
Dri-lube is like a stick that feels a bit like soap, you rub it on the surface of a belt that makes contact with pulleys and if they were the source of the noise it generally shuts up. But if you've replaced the belts recently it's more likely the idler pulley or alternator pulley.
 
thanks Tony! I'll try a bit of silicone spray on the idler pulley. it could even be the alternator pulley even as it's recently been replaced and can't recall the noise being there before it was replaced. is there any solutions for the alternator pulley if that's what it could be?
 
your Alternator / pulley could be one of those Clutch types which is not just a pulley wheel like the original types. as mentioned spray the tensioner pulley first and if still noisey you might have to remove the alternator belt and run the engine to hear if its the alternator at fault.
 
rookie question which pulley is the idler? is it the smaller one directly below the alternator at the 7 o'clock position?
 
the idler pulley is the pulley that only has the drive belt on it , its job is to tension the belt. just look for the pulley thats mounted on a bracket on its own .
 
think I've located the idler pulley but just want to check. when looked at front of vehicle it's bottom left and has the thin belt on it and appaers linked with the power steering? also is inox as good as silicone spray even tho it has no silicone in it? sorry for all the questions
 
The YD25 does indeed have two idlers (two belts!). There is one down near the power steering pump as you describe, there is another higher up - if you're standing at the front of the car, leaning into the engine bay, put your right hand on the alternator, move it left about 10cm and drop it, you'll hit the idler.

The front face of the alternator is a washer that doesn't rotate, you need to spritz in behind it. Inox is almost the same as WD40. Silicone Lube is only marginally different to WD40 (it burns more readily too, WD40 is oilier) but silicone lube is more slick than WD40. The Inox should do ok.
 
had a quick spray of the top idler pulley yesterday so will see how we go over the next couple of days. I was watching the pulleys while the engine was running and the small pulley almost directly below the top idler and above the AC pulley did seem to be spinning a bit uneven with a slight distortion if that makes sense, so could possibly be that pulley?
 
There shouldn't be a pulley between the AC and the idler. There are 5 pulleys on the main belt, in clockwise order: crankshaft, water pump, idler (adjuster), alternator, AC compressor. There's another belt from the crankshaft to the power steering pump with an idler higher up (so 3 pulleys in total).

If the main belt idler pulley (between the water pump and alternator) is skipping, you may have solved the problem. If not, you might need to replace it.
 
https://goo.gl/photos/3gxqa4RxGK7fu3QT8

hi Tony in the above photo in clock wise rotation starting at alternator there is:
alternator
AC (big one bottom right)
crankshaft can't be seen but is very.bottom left
water pump
idler
but what's the other small pulley below the idler? or is the pulley the radiator fan is connected to not included in your listing? I've searched Google and can't find a diagram of the pulley layouts.
 
Not definitive from looking at the photo but it appears you may have an automatic tensioner.
 

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