Weird Whistling

[XenoBlitz]

This is very weird and it happened for the third time now..

I drive my Patrol every single day, but sadly, I do not get the opportunity to take the highway that often.

I drive in town for long hours, I take a trail for a few hours every few weeks or so and this never happens, but when I drive Patricia for more than an hour on the highway.. she starts whistling at me!

Its a very loud whistle coming from the front of the vehicle. (I would guess left hand side near the snorkel, but could be dead wrong!) Driving at 120 km/h or more tends to distort the origin of the sound so it could really be anywhere.
It only ever happens when I'm constantly maintaining 3000 rpm or more for a long period of time (like the highway) and its definitely the engine. When I step on the clutch and free she's quiet. When I step on the gas again, she whistles. Thus far I have tried but I cannot duplicate this effect while standing still. And it only happens after 100 km or so... The engine temperature remains relatively constant so I cannot say it s because she is getting hot.

Has anyone ever had a problem like this and where can I even begin to look for the source. Her airways are clean and as I said a few times, it only happens on long roads and only when I've kept a constant speed for a distance. The moment I'm back into a town, village or city she's all quiet again, no matter how hard I ride her.

[ricster]

I might be barking up the wrong tree here.... I had a whine, more than a whistle, which was caused by one of the belt tensioner pulleys bearings packing up. Mine is the 4.2 diesel, but I think this could be the whistle you are hearing. I took the tensioner off and replaced the bearings (dirt cheap from a bearing shop), and Bob's your auntie.

[Tinus lotz]

may be the wind making a wisle on your snorkel or roof rack?????

[ricster]

Hmmm... yeah ... could be wind noise as air is sucked into the snorkel @ 3000 rpm. You mentioned that when you do that speed/rpm and press in the clutch, the noise goes away. That's why I thought it could be a bad bearing. Turn the snorkel mouth 180 deg and try driving. If the noise is still there, then at least you have eliminated one thing.

[XenoBlitz]

Thank you for your input...

I can try turning it, but I doubt that is the case... This does not happen from the start.
If I drive away from Pretoria, the noise does not start until I'm somewhere close to Sowetho... If it was the wind, it would have happened all the time. Not suddenly started after 1h of driving?

[Tinus lotz]

i also think it might be bearing or propsharft or man it could be anything ????????you need to look and listen carefully what bugs me is when you trap the clutch it goes away???gearbox or rear diff ???

[Peter Connan]

Weird Wilhelm!

Does the noise change with small throttle adjustments? Did you perhaps notice if changing direction makes any difference, or fiddling with the air-con?

As you can probably see, I am also thinking it might be something like the vee-belt tensioner or one of the ancilliaries, but wonder if it can make that much noise...

[XenoBlitz]

I would say I'm 99% sure its the engine. The sound definitely comes from the front of the vehicle. Where exactly is hard to say. And if I drop the speed so that I can go below 3000 rpm with the engine still running it goes away. When I speed up above 3000 rpm its back. If I step on the clutch and rev the engine (while moving) the sound is there, when I lower the rpm again (with the clutch depressed) the sound is gone. So I'm not thinking transmission or drive train.

The sound is high pitch like a whistle, but it could also be slipping (of fan belts or something) but high pitch.

I did not fiddle with the aircon, but direction is definitely not a factor. North or southbound, same problem.

Slight throttle changes (above 300 rpm) seemed to make a difference to the intensity (volume) but the pitch remained relatively constant. (Louder when faster.)

[Peter Connan]

I am struggling here...

I can't think of anything inside the engine that would take that long to start happening, as the engine would reach a stable running temperature long before that, and this is the reason I am suspecting the ancilliaries rather than the engine itself. But I am often wrong?

With changes in direction, I meant on a smaller scale than that, for example when changing lanes or similar "swerving"manouvres, because I am wondering if it might be either the power steering pump, air con or alternator? Any one of these might warm up slower than the engine itself, and if faulty might partially seize and cause a belt to slip?

But this is just surmise though...

[Strandblom]

Hi Xenoblitz, check the exhaust manifold. My neighbor had a similar problem with his Disco. When the engine rev'ed above 2500 -3000 it also made a loud whistling sound. We found one of the nuts on the manifold was missing. This caused air to squeeze pass the gasket and made the loud whistling at high rpm. We replaced the nut and re-torqued the other ones. Problem solved.