240 General: tapping and juddering

[Clifford Pope]

Two faults have developed recently, possibly connected, or perhaps not.

1) There has always been a ticking noise from the valve gear, gradually getting more noticeable, and then recently louder and persistant.
I checked the tappet clearances, and found all spot on apart from one which was only 5 thou. I fixed that, but it made no difference. Not sure if a tight valve could make a noise or not.
After a week I checked the clearances again. All still correct, except that a different one was now 18 thou. I fixed that, rechecked after a week, and all still are correct.

None of this makes any difference to the noise. It is more noticeable when cold, diminishes when hot, and disappears above about 2000 rpm. It is related to engine load, disappearing when I press the accelerator.
So preumably nothing to do with valves and timing? Piston slap? Small end bearing? Broken piston ring?
The engine runs well, has bags of power, no smoke, doesn't use oil.

2) There is a vibrating judder when accelerating hard in lower gears, especially 2nd and 3rd, seems to be related to engine speed, in the 1500-2000 rpm range. It disappears above 2500.
It also does it a tiny bit on hard deceleration, say 20 - 10 mph in 2nd.

I've replaced a very worn prop centre support bearing and soggy rubber support, but it made no difference. Also gearbox rubber mounting, and checked the prop shaft joints. All free but no play.

It seems to be transmission, as there is no sign when revving the engine, and varies with gear selected.

Worn gearbox bearings? Something in the clutch?
It doesn't always do it. Less when hot, and sometimes goes away if I declutch and then re-engage.


I can't see any reason to link the two noises, except that both began at the same time.

[Derek UK]

Ticking noise. I've just posted this exact post on a similar question on the 700/900 section. Worth a try.

"Manifold to exhaust pipe gasket leak can make these odd ticking noises. Have a check with your hand after a cold start. Don't try this with a hot engine....."

Judder? As it can come and go after de clutching it might be the pilot bearing. Not something you want to consider until all else outside has been checked. You appear to have done the normal fixes.
When it goes after de clutching, is there no sign of the problem until you de clutch again?

[Clifford Pope]

Originally Posted by Derek UK

When it goes after de clutching, is there no sign of the problem until you de clutch again?

Usually, but declutching rarely works.
I noticed today it rarely does it when accelerating having just decelerated in the same gear. It seems to be a feature of accelerating having just changed up.

It does sound horribly like the resonating squawking noise the heater fan makes, which can often be quietened by turning it up and then down again.
The pilot bush could surely only make a noise when actually declutched - with clutch engaged the shaft turns at flywheel speed?

[Derek UK]

Yes the shaft turns at flywheel speed but if the pilot bearing is breaking up and not centralising it there is a possibility that it will be out of line and be putting pressure on the front gearbox bearing. This is why I asked if changed, maybe unpredictably, when you declutch. Do you get any odd noises when you reverse it up a steepish slope, up into a driveway perhaps, when slipping the clutch. Humour me here but that can also be signs of a bad pilot bearing.

[monkeh]

The juddering could also be the U joints on the prop. Normally give the whole prop a once over when I change the centre bearing. Not cheap but Its worth treating the prop as a servicable item. There are small bushes on the U joints on the prop... Doesnt take much to cause vibration. 1-2mm of play feels like the worlds going to end soon.

[Clifford Pope]

It's not the prop joints. I checked those carefully when I replaced the bearing - in fact I swapped the whole front section with rubber gearbox coupling for a good spare, and checked the sliding joint. All joints have no play but are free to swivel.

I tried the suggestion of trying it uphill in reverse to see if it does it then - no, it doesn't.
But the extraordinary thing is that merely driving 20 yards in reverse up a slight hill has entirely cured the judder in all circumstances.
How long this will last of course is an open question, but what's going on?
Something obviously was out of place or misaligned before, and now it's gone back into place.

[Clifford Pope]

I've now covered about 50 miles since the amazing cure, and the judder hasn't returned so far.

Interestingly, the knocking noise apparently from the top of the engine has also diminished - it's now just a kind of mild sewing machine chatter, and no worse than the normal Volvo valve tapping that seems quite standard.

I can't see what on earth the connection can be, unless one or both noises were actually being transmitted from somewhere else.

[wooble]

A broken valve spring maybe? It could cause strange valvetrain noise without disabling the car as well as running issues.

[Clifford Pope]

Further developments:
The judder has returned, but different from before. It is now definitely related to road speed, not engine revs. It does it in any gear, and dipping the clutch or slipping into neutral makes no difference.
It's not constant, and now occasionally makes a little scraping jangling noise, apparently from the offside rear wheel.

I'm now thinking brake pads, warped disc, or fouling handbrake shoes.
So I've dismantled that wheel. The shoe operating mechanism was a bit sticky, but even after freeling there was a rhythmic scraping as I turned the wheel. The disc seemed true, but the drum brushes the shoes on each rotation, as if warped or worn oval.
The wheel bearing perhaps had a bit too much play, and could be wobbled a fraction making a little knock. So I have swapped over the shaft/hub assembly and disc/drum. The shoes were new a year ago.

The result is an improvement, but the vibration is still there slightly. But of course all this may be complete coincidence just like the other things I have fixed. I'm now coming back to thinking maybe there is a slight imbalance in the prop shaft, and that vibration picks up and resonates with any other items that have play or imbalance.

The broken valve spring theory would make sense. When I checked the clearances I tested the springiness of each bucket, but I suppose that doesn't tell very much. If I took the camshaft off and lifted the buckets would a broken spring be visible? Otherwise it would be a matter of working along dismantling each one in turn.
I've used the "rope trick" before, so it's do-able without needing to take the head off, just a big faff looking for something that may not be there. A broken valve spring wouldn't get quieter as it warms up surely?

[Stephen Edwin]

It's a puzzle init.

It's road speed related, and occurs with the clutch disengaged, and also in neutral.

You've worked on the propshaft. Have any of the fixings worked loose since you re-assembled?

Ia a mounting anywhere soggy or worse? Even an exhaust mounting, even just out of adjustment?

And total check of everything from the gearbox output back. Including the rear suspension? Aything loose, even a steadyng arm, might cause noise &c. related to road speed.

Good luck.