So there’s a crankshaft bearing or two, obviously, and presumably a few others. What happens when they wear out?

I’m still puzzling over the vibrations coming from the engine in my Passat TD at higher revs. Just trying to pin down what the cause might be. It’s not bad now but I’d still like to work it out. Have tried loads of things – injectors, injection timing, pulleys, engine mounts, valve timing etc. I don’t think it’s the gearbox since it doesn’t get less when you put the clutch in.

Gonna maybe remove the engine to change the gearbox in the near future, anything else I can check when it’s out?

If your crankshaft bearings go the crankshaft itself will start whipping about and will cause a nasty knocking noise from the engine. Will eventually lead to the crankshaft cracking/failing and can cause a whole host of other problems along the way (failed crank oil seals for example). If you’re removing the engine then get it up on an engine stand and drop the sump. Should be obvious if the crank bearings have gone.

camshaft bearings…..friends Fiesta had knackered camshaft bearings which failed on the M20. BIG bang, oil smoke everywhere….pull over and pop bonnet…..tons of oil smoke pours out, engine bay covered in oil……girl who owned the car asked if it looked bad just as a 3″ section of camshaft rolled out from under the car. Couldn’t have timed it better.
It was making a hell of a lot of noise before that point, but not a lot of vibration.

Could be a worn/broken engine mount? Flywheel?

Once you’ve heard big ends on their way out, you never forget the noise. On a petrol engine it starts as a faint rattle at high revs (like a diesel engine rattle) which slowly turns into a banging noise at any revs, then there’s usually an odd ‘THUNK!’ and it stops and won’t go any more.

If I suspected bearings, I’d unload sharpish!

(Note – Solamanda, if you’re reading this that’s NOT why we sold the Vectra, honest! 🙂 )

Right, so it’s not the main bearings – thanks folks 🙂

Could be a worn/broken engine mount?

Fixing that was one of the many things that have greatly improved but not cured it.

Flywheel?

What goes wrong with flywheels? Something being out of balance would definitely fit with the symptoms.

On a petrol engine it starts as a faint rattle at high revs

I got that but only in a fairly narrow rev band at about 3k – assumed it was just something not fixed down possibly, resonating with the vibration caused by something else.

Interested in the flywheel hypothesis…

Dual mass flywheel? Seem to remember these letting go in VAG cars and causing some issues

No, it’s pre-dual mass flywheel. Don’t have any of the specific symptoms. Although.. there is a strong vibration (not the same one as at high revs) at between about 1.1 and 1.3krpm… Hmm. Could one have been retrofitted?

I believe some people replace the dual mass with a standard unit, but would doubt anyone would go the other way due to the cost.

How old is the car? What engine? 1.9TDi?
Could be a dual mass flywheel as mentioned above and I think that they can be quite fragile. I think all 1.9TDi VAG engines have a DMF.

Presumably you get the symptoms while sat on the drive, just revving the car?
Could it be an injector not firing correctly through a certain rev range, and causing a bit of an imbalance/lumpiness? Bit of a longshot.

Tappets can sometimes sound like bearings. Relatively easy to check.

Sorry bit late on replying…so it’s a normal flywheel. As said, doubt a standard would be replaced with a DMF, but perhaps something to get checked?

It’s a 94 1.9 TD – that is, indirect injection not a TDi.

As for injectors – they are new, but I am wondering if there might be a very small leak in one of the high pressure lines. I don’t see anything, but they are a bit battered, bent and old.

It does it with the car moving or stationary, there’s vibration at high speed and the narrow low speed band whatever driving conditions are, and also accelerating AND decelerating. So that tends to rule out a fueling issue as it wouldn’t do it when decelerating as no fuel is injected.

I am considering rebuilding the injector pump next. Could be something loose in there.

Could it be the exhaust rattling and making contact somewhere?

Identifying noises over the internet is pretty much impossible – just a case of thinking of anything that might make a noise on an engine 😀

Have you checked belt tensioners (timing and aux belts) – autotensioners can reach the end of their travel when the belts stretch, causing them to rattle against their stops. Unless its way loose I’d not expect too much vibration from it.

Remove the gearbox from the equation by pressing the clutch pedal – that disengages it, then rev the engine – noise still there? Not ‘box.

Having suffered a shattered clutch I can say you’ll notice any damage to fly or clutch in that it feels like you’re on a massage chair when even the slightest bit has broken off, it comes and goes through certain harmonics, but never made a noise.

It could be worn little ends, cracked rings… the list goes on!

(Note – Solamanda, if you’re reading this that’s NOT why we sold the Vectra, honest! [:)] )

</stalker mode>

just a case of thinking of anything that might make a noise on an engine

Well that’s basically what I’m asking. I get some ideas, go fix them, it gets better but not cured, so I come back and ask for more things to fix 🙂

The noise I think is caused by the high frequency vibrations resonating in the exhaust and the rest of the car.

PS already determined it’s something in the engine. Still does it when clutch is in, and it’s not fuelling since it still does it when decelerating. Don’t think it’s compression as it ALWAYS starts instantly regardless of temperature or even fuel.

Wish I was nearby to have a listen. Can you not get a capture on a video cam (hard to get the sound to match I know) but it might help.

Presume you’ve tried the screwdriver-stethescope method of finding rattles?

Well, the slight resonant rattle only comes on at 3krpm, and when you open the bonnet with the engine at that speed you can’t hear a thing besides the deafening roar of 1.9 litres of firey mechanical inferno.

Tried listening with the screwdriver, was inconclusive. But in any case, it’s the vibration I’m chasing. Just starts to vibrate above a certain speed.

Where are you CK? You’d probably only laugh at me anyway since it’s actually pretty decent for an old car… It’s just become something of a project for me. Or an obsessive quest. It is large and white after all…..

Glasgow – not much help I’m afraid! I wont laugh at you, I’ve sunk thousands into my (also large and white) 4 wheeled friend just because I like it!

I’d ask are you sure its not “normal” for that engine. Can you eliminate large chunks of engine by doing things like removing the aux belt to take out alt/tensioners and a few other bits – obviously thats impossible if its running your fuel pump – not sure on that engine. I’ve had some scary rattles at high revs from alternator support brackets having come loose, would vibrate too but wouldnt have thought enough to feel. About the only things I’d say that were big enough to produce a vibration you’d feel while driving would be crank/cams/pulleys or a misfire. Anything else I’d question its ability to vibrate.

Usually the screwdriver method works a treat – even better if you can put ear defenders in and rest the driver against the defenders – all other noise is deadened by the rattles from the engine are amplified.

I’d ask are you sure its not “normal” for that engine.

Well, that’s a good point. It is a diesel, and it is 15 years old… But I don’t feel that VW engineers would’ve let it off the production line quite as noisy at a time when they were trying to convince people to buy diesel.

There’s a known fault on those engines where the lower timing sprocket comes loose on the crankshaft nose and mashes it up, causing the crankshaft pulleys to wobble. This was one of my first thoughts, but the crankshaft nose looks undamaged. The accessory drivebelt pulley has a rubber piece in it that’s a vibration damper – I replaced that as the existing one was out of true, and it is better now but still not quite true. The power steering pump one isn’t true tho. I was thinking that these things were too small to make a difference now but I dunno. If the new pulley is out of whack then that implies the crankshaft nose is slightly damaged or I’ve done something wrong…

I was considering taking the engine out to change the gearbox when my father in law’s over (assuming we’re still in the country by then) and then I’ll maybe take the crankshaft out and take it to a machine shop to have it checked out. Then why not go the whole hog and recondition the whole thing.. :

Could be the crankshaft pulley. Some have an inbuilt damper that de laminates causing an imbalance thus vibration. The one on my scudo van let go. Has been known to take the end of the crankshaft with it. Worth having a luck even just to check that the crankshaft pulley nut is still tight.

Replaced, Inbred456, as per the previous post but I may investigate further.