Engine whine

[david.g.chapman]

I have a slight whine coming from the engine, tied to engine speed. The whine is still there when the fan belt is removed, or when the clutch is disengaged. If the timing chain tensioner is backed off so that the chain rattles the whine is still there.

You hear it most between 2000 and 3500 rpm, when it goes up into the 10KHz + region and I can't hear it as well.

Any ideas?

Dave Chapman.

[robertverhey]

Might be a dry points heal in the distributor? In which case get onto it quick before it overheats and melts (why do I know this?)

Robert

[david.g.chapman]

I have just checked the distributor - and it seems fine, with some grease on the points heel.

Scratching my head on this, I can only think of:

1. Jackshaft to distributor gear mesh

2. Jackstaft to oil pump gear mesh

3. Pilot bearing or gearbox input shaft bearing (I have the 4 speed box) - note no change in whine at all when the clutch is operated. The clutch operation is also silent on the move.

Can anyone eliminate any of these from experience? It is hard to trace the source of the whine - somewhere around or in the engine.

Dave Chapman

[rgh0]

The chain adjustment sprocket has a plain bearing that can whine if it is starting to fail cant think of anything else other than what you listed.

cheers
Rohan

[david.g.chapman]

Thanks very much Rohan .

I have whipped out the tensioner sprocket assembly and taken the sprocket with its bush off the brass carrier. The bush had been merrily spinning inside the sprocket - that's not good, especially as I am off to France for a 2000 mile trip in 2 months! There was also a fair amount of sideways play in the spocket - 1mm at least. There are no oil lubrication channels on the outside of the bush (because that is not supposed to move) so it could be the source of the whine.

I will find out in due course, but even so - that has to be done.

I can discount the pilot bearing as the whine was still there in gear with the clutch engaged. The pilot bearing is static under those conditions.

I can live with the jackshaft if that is the cause as it is unlikely to fail anytime soon.

Thanks again,

Dave.

[david.g.chapman]

More on this peculiar whine.

I have replaced the tensioner sprocket and its bush, and also the special bolt that forms the inner bearing surface for the bush. The whine however, is still there. I am still in Rohan's debt though - nice one .

I did a little calculation as to whether the jackshaft might be causing it. At 3000rpm the whine is 2-3KHz in frequency. Now at 3000rpm the jackshaft rotates at 3000/2 or 1500 rpm. This is the same as 1500/60 Hz, or 25Hz. The are 11 teeth on the distributor skew gear, and a similar (or the same) number on the oil pump gear. The fundamental frequency of both gears is therefore 11 x 25 or 275Hz. That's much too low to be the cause, unless any gear experts know differently.

As I mentioned before, the whine is unchanged in neutral with the clutch out (pilot bearing rotating and gearbox input shaft static) and in gear with the clutch in (pilot bearing static and input shaft rotating) - so it's neither of those, nor anything further along the drive train.

So I am stumped. I suppose it could be that the chains whines a bit anyway even when correctly adjusted, and that now I have set the tensioner to stop the rattling I notice it more.

Ho Hum

Dave Chapman.

[robertverhey]

I assume you've done the "stethoscope" thing with a piece of tubing to narrow down the location?

Robert

[Lincoln62]

If there's a split in your gearlever boot you can get a whine. I did. New boot, no whine.

Pete
66S2

[1964 S1]

Stethoscope with the metal rod is best on this one.
Does it make this sound sitting still, do you hear the whine in the engine while the car is not moving?
Eric

[69S4]

Hi Dave

Does it whine more when the engine is hot or cold? Thermal expansion is going to change the chain tension so if it's chain related you'd expect the pitch to alter as the engine warms up.
I've always had a slight whine from my engine that lessens but doesn't go completely as it warms. You can hear it if you stick your head under the bonnet but not inside the car. The noise has survived cam chain changes, a new distributer, oil pump and various different oils. I've wondered about it but so far just accepted it as part of the engine's characteristics. One of my Honda motorcycles a similar characteristic, a really noticeable whine when cold (either cam chain or primary gear mesh) but is silent when hot.

[david.g.chapman]

Thanks for that everyone.

I have just got hold of a mechanics stethoscope (the one with the rod probe) and will have a go tonight. I think the whine is slightly louder when the engine is hot. The whine is the same with the car stationary or moving.

Dave.

[gjz30075]

Dave, can you post a Youtube video of it? We'd love to hear it.

Greg Z

[david.g.chapman]

I have posted a video on YouTube - search for Lotus Twin Cam Engine Run (Whine Noise Excessive?)

Near the start of the video I zoom into the area where the noise is loudest, below the cam cover near the exhaust sprocket. Those stethoscopes are very good! There is far less whine with the probe on the gearbox bell housing, or the distributor/jackshaft area, or on the inlet side of the cam cover.

I suppose that side of the chain is under load the most, so makes the most noise?

I wonder if the cam bearings can whine if worn. They where OK not so many miles ago.

Dave.

[paddy]

It's near to the timing chain guide - I wonder if the chain is snagging on something there?

Paddy

[david.g.chapman]

Hmmm..

That could be the source, Paddy. I have a Burton chain slipper fitted with a thinner layer of rubber then my old one. The chain also goes onto it at a slight angle looking down from the top (as I remember). I think the links are passing that point fast enough to cause a whine as well.

Cam cover off again tomorrow!

Dave.