Failing crankshaft pulley after 20k miles?

[bennetimo]

Hi, I have a 2017 MK8 Transit that had the crankshaft pulley fail at 210k miles. The rubber inner completely deteriorated and fell off the engine block leaving the metal part still bolted in, as looks to be the common way these fail.

All was fine for a while until a few months ago there started to be a pretty horrible rattling noise coming from the engine bay around the pulleys. It doesn't happen all the time (possibly seems related to the ambient temperature outside, being worse when cold maybe) but when it's making the noise you can really hear it if you're standing outside!

Here's a short clip of what the noise sounds like from under the engine near the crank pulley: https://streamable.com/0nociq

The crank pulley was only replaced 1.5 years ago and has only done 20k miles in that time, so it seems a bit premature to be failing. But I've since upgraded the alternator, replaced the idler pulleys, the tensioner, and most recently the viscous fan and fan pulley and the noise is still there. The sound goes away completely if the belt is off too.

I ruled out it being the crank pulley at first given how new it is, and thought it was the fan/fan pulley as it has a plasticky sort of rattling noise and it was hard to pinpoint exactly where it was coming from. But having replaced those the only thing left pretty much is the crank pulley again! And it definitely looks like it's wobbling quite a bit while it's spinning as well, way beyond what looks normal.

The one that failed before was an original Ford one with part number 1748942/BK3Q-6B319-CB, and it was replaced with a Dayco DPV1210 along with a new belt.

Does it look like the crank pulley is failing again? And if so, any recommendations for a replacement? I usually like to get original oem parts after some bad experiences with aftermarket ones, but a new original Ford pulley is £307 direct from eBay, and that's with a 10% off discount at the moment! (https://www.ebay.co.uk/itm/393457881345).

I could get a Corteco 80004875 instead for ~£94 delivered from Autodoc (https://www.autodoc.co.uk/corteco/7706121) which according to a couple of posts I read on here might even be the oem one for the Transit anyway, just without the branding?

Curious for any thoughts!
Cheers

[Sam123]

I'd go with the Corteco one. I did it a few years ago, and the Corteco part clearly had the Ford marking ground off.

I don't usually much rate Corteco, but Ford seems to use them for a few of the rubbery parts (same for the motor mounts). Mine's been on now for 30k miles, and no problems.

Autodoc code 'SAM' should give you 5% off.

Edit: I can't play your video so don't know if the pulley is the problem, but if you conclude it is, see above ...

Another thing to give a Paddington stare to is the alternator. I had this fail on mine recently, and that gave a horrible grinding squealing noise, and the source wasn't obvious. Maybe try loading up the alternator with as many electrical consumers as you can and see if the noise changes. Or take the belt off and give it a good twistin'.

[metalworker0]

What does it sound like if you turn the AC on or off

Yes, video played and i was able to slow it down to half speed.. but that didn't help .. i can see it momentarily after it stops, reverse direction a few degrees.

This may help with your diagnoses

https://www.youtube.com/watch?v=Al_CUlmSKtk

all the best.mark

[bennetimo]

Thanks both for your thoughts!

I'd go with the Corteco one. I did it a few years ago, and the Corteco part clearly had the Ford marking ground off.

I don't usually much rate Corteco, but Ford seems to use them for a few of the rubbery parts (same for the motor mounts). Mine's been on now for 30k miles, and no problems.

Autodoc code 'SAM' should give you 5% off.

Edit: I can't play your video so don't know if the pulley is the problem, but if you conclude it is, see above ...

Another thing to give a Paddington stare to is the alternator. I had this fail on mine recently, and that gave a horrible grinding squealing noise, and the source wasn't obvious. Maybe try loading up the alternator with as many electrical consumers as you can and see if the noise changes. Or take the belt off and give it a good twistin'.

Cool, yeah I went with the Corteco one in the end as I couldn't justify >£300 for a pulley! I had already bought it before your post though but found another discount code online, thanks anyway

I'm pretty confident it's not the alternator as I've upgraded that fairly recently, and the sound definitely seems to be coming from lower down. It felt like it was quite loud around the viscous fan (one of the reasons why I changed that), but it might have just been the crank pulley the whole time, but I overlooked it assuming it couldn't be that for a while because of how new it is.

What does it sound like if you turn the AC on or off

Yes, video played and i was able to slow it down to half speed.. but that didn't help .. i can see it momentarily after it stops, reverse direction a few degrees.

This may help with your diagnoses

<span class="skimlinks-unlinked">https://www.youtube.com/watch?v=Al_CUlmSKtk</span>

all the <span class="skimlinks-unlinked">best.mark</span>

Yeah it wasn't the best video as it was so short!

Here's a longer version when it's making the noise: https://streamable.com/m9wt44
And this is a closeup of the crankshaft pulley when it's NOT making the noise (but it looks like it's wobbling a LOT): https://streamable.com/b94mo8

Presumably as it's a vibration dampener/harmonic balancer some minimal play is normal, but mine looks like it's moving in and out a good 5mm. Presuming that's not normal??

My van doesn't have AC, but I have verified a few times that the noise isn't there if the belt is off. That led to me thinking it was one of the pulleys on the accessory drive, as the crank pulley is still obviously spinning without the belt on so I ruled that one out and because it was replaced only 20k miles ago. But having replaced pretty much everything else now it's the only thing left (other than the water and power steering pumps), and I'm guessing with no load attached to it it's not under so much stress and the noise isn't triggered. But adding the load to drive is causing it to vibrate a lot more. That's my theory anyway.

The other thing that's interesting is it doesn't make the noise all the time. I thought it was temperature dependent, but after after a few more drives it seems like it is less likely to make the noise when first starting up after not being driven for a few hours, but after driving anywhere as you're pulling into stop you can really hear the loud rattling noise even from inside the cab. And when pulling to a stop at a roundabout or traffic light you can hear it too. Not sure if it goes away at high speeds like on the motorway as I can't hear it then, but that's probably just because the ambient road noise is too loud.

I've now ordered a replacement pulley but I am a bit concerned with how quickly the last one has failed if this turns out to be the cause. Could there be some wear on the actual crankshaft/mounts contributing to severely reduced life of the pulley? Hoping I just got unlucky with the Dayco one and the Corteco one will fix it, and I've ordered a new belt as well to even rule that out being a factor.

[metalworker0]

Second video would be a good sound track for horror movie

Wonder if it's possible for a tiny stone off the road to get held behind a pulley.

all the best.mark

[bennetimo]

Ha yeah it doesn't sound great, makes a racket when pulling into places that probably doesn't go unnoticed

I think it's too consistent for a stone, and it's been happening for a good few months now. It's always the exact same plasticky rattling noise and seems to be on every drive, but not when initially starting the engine before driving sometimes. So sods law when I went out to capture that last video it wasn't making the noise that time!

[bennetimo]

So we got round to replacing the crankshaft pulley with the Corteco one today...

Check out this before and after slowmo comparison..! Think we got to it just in time before it completely failed!

https://streamable.com/dokw2o

The Dayco one that was on there was completely buggered and the metal ring that was inside had separated and was moving out of the pulley and knocking against the engine block. It was probably what was causing the plasticky rattling/knocking sound as it was bashing around on each revolution, but it definitely seemed worse today as we haven't noticed any metal sliding out of the pulley before.

When I unbolted it and took it out the metal ring just came off in my hands...

PXL_20260406_091056212~2.jpg

With a big crack down the side of it

PXL_20260406_092047606~2.jpg

And there was some wear/rough ridges on the engine block where presumably the metal band had been rubbing against it so many times...So not too impressed with the Dayco pulley! I had to sand it down a bit with some 800 grit sandpaper to make it nice and smooth again before bolting the new pulley back on. Either that or the original Ford pulley caused the wear before and it wasn't cleaned up by the garage when the Dayco was bolted on, which might have contributed to it failing a lot sooner (only 20k miles). But that seems unlikely as the rough ridges were quite obvious, and the original one failed in a different way (the rubber gave way leaving the bolted part still attached) and from what I remember it came off cleanly.

It wasn't too bad to replace, we took off the viscous fan and removed the radiator cover to get a bit more access (even then we could only just get in a with a normal breaker bar to loosen the bolts). And we picked up the Nielsen crank holding tool cheaply on eBay which worked well but was a bit fiddly to find the right position and get on sometimes but it all went pretty smoothly. The only trickier bit really was doing the second degrees phase torquing up the bolts, trying to get enough space for the torque wrench with the holding tool together in there at the same time. The 15mm socket we had wasn't deep enough to allow the torque wrench to rotate round without hitting the tool, but with a small extension it worked great. Put on a new belt too for extra peace of mind.

So yeah very happy we replaced it today, and the noise has finally gone!