1.6D intermittent knocking / clacking

Hi All - would really appriciate some urgent help.

I have a 1982 Mk1 Jetta with the 1.6 Diesel NA. Owned for 15 years, and I've restored the car (mostly myself). It has never let me down, other than a faulty (new) wheel bearing shattering. Other than that, it's just been the regular with a worn starter motor and a couple of alternators. I drive the car a lot, have covered about 100k miles and its done many trips across the UK and Europe. I regularly do a fuel/oil/air filter service every 6-12 months and runs really well. Starts fine and no leaks.

The diesel pump was rebuilt quite a long time ago, 2015-ish and the top end was rebuilt in 2021 by a specialist as it deserved some love and I wanted to reduce the smoking. It was an engine out job, with everything being refreshed, rubber, paint and all. It has ran so sweet since…up until now.

In the last couple of weeks i've noticed an intermittent clacking sounds and a very subtle vibration, almost coming in waves (humming and vibrating for a couple of seconds, then not - on repeat) at all revs but most noticeable at tick over (the noise particularly) and holding at about 2000rpm (at which the vibration is most noticeable).

I checked and the alternator belt was loose. I also remembered a similar noise when the alternator went last time, almost like a crack of a spark sound.

I checked the alternator with a multimeter and everything seems fine, maybe over charging slightly (14.7V on idle, dropping to 14.6 with revs).

I grabbed a new belt (and have ordered an alternator just in case), however, after fitting and tightening the new belt the noise was still there so I knew it wasn't a loose belt issue. On closer inspection, I noticed the crankshaft pulley looked slightly wobbly. I took the alternator and new belt off and ran the engine again and the noise is still there.

Typical Google search filling me with fear - I thought I'd ask the guru's here!

Here is a video - you can hear the normal diesel engine noise, but then extra sort of dry rattling / crackling sound (it does this without alternator and belt too as mentioned)

I've had a local (VW but not classic, specialist) mechanic look at it who felt it was just the noise old diesels make, but recognised I would probably know the difference between how it currently sounds vs how it normally sounds. I've ordered a new crankshaft pulley wheel incase the current one is warped and the mechanic is going to look at the engine timing on Wednesday.

Do you guys have any other thoughts, any experience of this? Could a warped crankshaft pulley alone make these noises / vibration?

I made a list of all the previous forum chats related with the following outcomes, if anyone has any thoughts:

• Warped Crankshaft pulley  /  Timing out  /  Diesel injector heat shields loose  /  Stuck Wrist Pin (fixed by using lighter oil)  /  Crank bearings worn  /  Piston bearing worn

The other thing, I did an oil service with new filter about 8 weeks / 500 miles ago, oil level is fine and used a recommended Shell Helix HX710w-40 oil which I'd not used before.

Your input would be very much appreciated - I'm supposed to be driving to Italy in it on Friday and of course this happens now (glad it is before rather than during though!)

Cheers, Toby.

Not on my diesel but I have a Service Technician induce a crank gear shear on me.  

They replaced the timing belt, and used 110lbs of torque on my 12Pt bolt.  That drove the bolt in to the back of the crank and bent the tip. which backed out as it was stripped and allowed the Crank gear to back out occasionally.  The 6pt bolt is 110lbs, where as the 12pt was only 60.  Had to buy a buy a new crank.

There was a bloke on one of the forums that had a similar issue, and he opted to take the pulley and Drill it and the crank, He tapped the crank and used a allen bolt to bolt the pulley in place.  

I had to Drop the Tranny, pan, and oil pump, then unbolt the front and rear oil seal carriers to remove the crank to
take it to my machine shop to get the bolt out.  They had to use an industrial Impact and 400LBS of air to remove it as I needed the seal carriers.

Old destroyed bolt, sorry for the 1mp res, but that was state of the art but a few decades ago.



Crank pulleys shouldn't wobble.

Thanks Briano1234 - maybe too technical for me to even begin doing any of that!

Based on what you have said happened - would the noise be noticeable almost immediately or after driving for a few miles, few hundred or only after a few thousand? I reckon I've done about 10-15k miles in it since the belts etc were last touched and it has been running sweet up to a week ago. The top-end was done by a proper VW classic garage (Garage87 in UK) who know these engines and they put all the belts etc on after the engine work.

Thanks

 

It was the timing belt - it gave up on my way to take the car to a specialist to have a look…

Nothing to do with the crankshaft pulley after all.

Will keep this thread updated where possible, but fearing the worst as had to keep the car running as had no hard shoulder to pull in on. It got very sluggish and wanted to cut out but did keep going and then was ticking over while I stuck my head in to have a look before switching off.

Hoping the whole belt didn't sheer - reckon something would have stopped the car running if it had?? 

After a day of checking all the responses were 'its fine, they all sound like that' put me in a false sense of security to get it a few miles to get a proper look!

Beat me to it.
I was going to suggest the timing belt or the belt tensioner bearing.

If the belt  had completely snapped the engine wouldn't run because the valve timing would have been stuffed, So you got away with that amazingly well. Change the idler/belt tensioner as well as the belt because I do suspect it is/was the belt tensioner bearing making that metallic noise

When I had a belt skip 2 teeth on a drive, it put Number one Piston through the head and number 3 Welded a valve to a piston. I hope for the best.  

• Jetta dropped off at Crazy Quiffs (via AA truck) at midnight 

• Got the call from CQ in the morning to say I’d been very lucky and likely not catastrophic 

• After further investigation, diagnosed as the auxiliary assembly having come loose and chewed itself up but only partially destroyed the belt (hence me finding chewed up belt in the bay and jumping to conclusions!)

• I’ll upload images of the broken parts for reference (I didn’t get photos of them in situ)

• As QC are magnificent, they had all the parts and determination to fix it for me

• By the end of the day, it was done! Hero’s.

• I got there 24 hours after dropping it off and it’s been running like a dream since!