Whistling oil boiler

My oil fired boiler has started whistling while running. The high-pitched whistle starts about 10s after fireing up, stays pretty constant while running and then tapers off after the boiler extinguishes itself.
Any suggestions as to what might be wrong? I've seen various suggestions around a build up of limescale, but they seem to normally be referring to a much lower pitched rumbling sound.
Thanks, Piers
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Make and age would help.. Fan motor bearing sounds a possibility.
Al
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1. Build up of crap on the fan or in the housing 2. Motor bearings failing 3. Problem developing in the oil pump 4. Oil starvation in the feed to the pump caused by clogged filter element either at the tank, between the tank and the boiler or within the pump itself 5. Firestop fuel valve almost closed
If it takes 10s after firing it does suggest a fuel starvation problem as a vacuum builds up in the pump in this time
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On Wed, 2 Feb 2011 08:07:16 +0000, Piers Finlayson wrote:

Define "fireing up" do you mean blower starting or when the ignitor fires to light the boiler some seconds later?
Thinking that it might a worn jet if it hasn't been serviced/replaced every year or so. Though I'd expect that to stop PDQ after the blower stops.
Kettling due to scale can be quite high frequency but I wouldn't call that sound a "whistle", ie a single tone, it's more high freqency noise.
--
Cheers
Dave.




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On 2011-02-02 12:57:53 +0000, Dave Liquorice said:

A Mistral Diamond. No idea of age, but instructions dated 2000.

The latter (i.e. after the whumpf - a techincal term).

The jets haven't been serviced or replaced for a few years. Whistling stops fairly quickly but not instantly - fades away over the course of a few seconds. Of course it's not doing it now.

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A worn jet usually causes poor atomisation leading to loss of efficiency due to degraded combustion and eventually soots up the boiler. Not servicing an oil boiler is false economy
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On Wed, 02 Feb 2011 14:35:02 +0000, Piers Finlayson wrote:

Our propane-burning forced-air furnace sometimes does it, too, but not always. As it's not consistent I've always assumed it's something to do with atmospheric conditions (temperature, moisture content in the combustion air etc.) rather than any kind of fault, but maybe it really is a maintenance issue... (the furnace control board never displays any kind of fault condition)
cheers
Jules
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On 02/02/2011 14:35, Piers Finlayson wrote:

Is that a Metric whumpf or an Imperial whumpf?
--
Dave - The Medway Handyman www.medwayhandyman.co.uk

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It's probably where it's sucking in air through the mixture adjustment flap on the burner.
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