Low Whistle when hot.

[Richard Lorand]

Could anybody suggest the source of this whistle. It usually occurs when I slow down after a long run down the motorway of after it has been stopped and started. Its a Colorado 1998 KZJ95 that had 109k on the clock two years ago and now had 130k and has always had this problem. It does not do it on tick over and is usually between 1 and two thousand revs but at a constant pitch it is not engine rev related. It very rarely does it when stood still but appears to be round the fan area. If it was the fan, pullies, alternator or water pump the sound would alter with engine revs but it doesn't. It almost sounds like air intake whistle but is from the wrong area. I would like to get it sorted before I ship it to Canada next year for a grand tour. Anybody have any suggestions.

 

[AdventureWagon]

Sure it's not the vicious fan clutch? Should feel resistance if you spin by hand when engine off, and it should stop in 1 revolution.

Auto or manual trans?

 

[Richard Lorand]

Manual

 

[Shayne]

Between 1 and 2000rpm your turbo is winding up , you sure thats not what your hearing ?

Took me so long to find a whisle that did not sound healthy i eventually pulled over on a motorway a couple of hundred miles away from home and on my way to Romania because i thought my turbo was going to explode .

It was the crankcase breather pipe which had obviously split long before in a minor way and undiscovered finally made a horrendous noise when it split properly , though not so bad i couldn't salvage it by chopping a bit off the end and taping it up to refit and continue on the trip .

 

[Richard Lorand]

Just to mention no over heating and air con works fine.

 

[Richard Lorand]

Would I not hear the turbo when cold as well. I only get the whistle when engine very hot.

 

[Shayne]

Could be belt squeal

 

[diggerdave]

Spring stretch mod?

 

[Richard Lorand]

No spring stretch mod.

 

[diggerdave]

Have a look via the search function... a spring in the fuel supply can cause a whistling noise in the fuel supply line that's most prominent in the passenger footwell. A VERY simple fix that's worth a try, in case it's never been done. (If I remember right a guy in South Africa discovered it 20 years ago. Most have been done though.)

 

[Richard Lorand]

Many thanks for all your suggestions. Maybe the vicious fan clutch needs a closer inspection. AdventureWagon suggests that when you spin the fan it should stop in on revolution. When I spin mine it stops dead after I let go. Is this good or bad. As stated previously there is no over heating, which is usually a symptom of vicious fan failing.