A few weeks ago I posted a message about a strange whirring noise from my 1995 940 (http://www.brickboard.com/RWD/?id=720845).

“Can anyone please help me to diagnose the source of what I can only describe as a whirring sound which comes from somewhere in the engine.

It occurs for a short time immediately after the engine has been started and disappears after a couple of minutes or so. It only occurs when the car has been standing overnight and when the engine is cold and it seems to coincide with the recent change in weather and drop in air temperature (although that may be a coincidence!).”

We still have the noise and have not diagnosed its source yet.

The noise remains when the fan belts are removed, so that rules out the alternator, fan, water pump and power steering pump.

The local Volvo dealer were certain that the noise was linked to the timing belt, so they replaced the timing belt and tensioning bearing – but the noise is still there.

Since noises are very difficult to describe, I managed to make a recording of it using an ancient portable cassette machine and I have now upload it to a web page as an mp3 file (the file size is about 1.5Mb in all).

This is the link to the page:
http://homepage.ntlworld.com/jd.guest/Volvo_noises/index.htm

I would be very grateful of any further advice and perhaps listening to this recording may help.

Many thanks - Jonathan

I've listened to your recording and assume it's the low whirling sound that, as you mention, sounds like gears meshing. It reminds me a little of driving in reverse in a manual trnsmission. I'm thinking that sound could also be something rotating at high speed that is flipping against something stationary, like when I used to attach a playing card to my bicycle so the spokes would flip against it. You've said the dealer replaced the timing belt. Did they also replace the tensioner? Could the belt be rubbing against something? Could the starter not be disengaging? Could it be comming from the distributer? You also mention using a screw driver and a hose to listen to various parts of the engine. I recommend you use an actual mechanic's stethoscope. The one I have consists of a conventional stethoscope connected to an egg-shaped sound chamber which has a thin probing shaft attached to it. The idea is to touch the probe to various metal parts and listen for the vibration. It's same idea as the screw driver, but much more effective.

Dear jkordzi,

Good a.m. I think you're onto something. The noise is almost certainly that of an electric motor.

Volvos have few of these: starter, radio antenna (some models), fuel pumps, power seat(s). The only one likely to be clearly audible in the engine bay - and over the noise of an operating engine - is the starter.

It must be possible for the starter to remain engaged with the flywheel, once the engine has caught. I presume this would impose great strain on the starter motor, leading to premature failure. Perhaps the starter solenoid is sticky, and disengages slowly (which might account for the sound fading). A sticky starter solenoid might also be consistent with this sound appearing after the car has been out in the cold, as cold tends to make lubricants congeal.

If the car, is put up on ramps (trans in park, emergency brake on, rear wheels chocked) and the engine turned on, one need only put a hand on the starter to be able to detect quickly if it is turning.

If it is still turning, once the engine is running, that is a problem and likely the problem.

Hope this helps.

All the Best for a Good, Healthy 2004: for you, your family, and your cars!

Yours,

spook

Thanks jkordzi and spook for you replies. I’m glad the recording was a help.

As a kid I can remember doing just as you mentioned with my bike using an old postcard, and from what I can remember the sound which my engine now makes is very similar to that of the postcard on the spokes.

I think the starter motor theory is one which is well worth exploring further. It had crossed my mind earlier, but I sort of dismissed it as I thought the sound may be coming from further forward in the engine. As there isn’t much left to look at, and knowing that sound can reflect is strange ways in a confined space, I’m sure that it could be a sticky solenoid or similar, I’ll have a further look and listen.

One point that adds to the theory, is that the previous owner had the engine compartment valeted (steam cleaned?) before putting the car up for sale. The car remained in his garage for 2-3 months before we bought it during this summer. I suppose that if some water got into the starter motor and it was then left idle, that there could be a slight build up of contaminants on the motor, solenoid shafts etc. resulting in sluggish action and hence the possible slow disengaging of the pinion. If after further examination (external) I find that the starter needed further examination (removal) is it possible to lubricate its main parts?

The dealer thought that the tensioner was the source of the noise. It sounded a bit dry, but was not particularly rough. The camshaft oil seal started to leak a bit more so I asked them to replace it along with the tensioner and also fit a new timing belt (and check for the belt rubbing on the case). I think they were convinced that this would cure the noise forever.

Alas no! - Never mind, we can rest assured that the problem doesn’t lie in this area anymore.

I had thought about a stethoscope, but it’s not something that I could find locally, but I’m sure it would be a worthwhile investment for the future. (perhaps I can also use it to check my blood pressure during trying times with the car!)

Many thanks for your help - Jonathan

I too listened to your recording, what an excellent idea.
I have had better luck listening for noises with a simple plastic tube (3/8" or so) stuck in my ear and passing the other end around suspect areas. The pick up of sound will be very directional so bring the tube in at different angles. Practice around the alternator first, you wll be amazed what can be heard.

That is a sound I have never heard and my guess would have been power steering pump or something rubbing on the timing belt teeth. To me it does not sound metallic. I think too fast a frequency for the distributor. Maybe starter not disengaged or something else rubbing on the flywheel teeth?
--
David Hunter