Engine rattle when cold

[vincentvg]

My V70 with the Audi lump has only covered 66,000 from new: regularly serviced. It suddenly developed a rattle when cold - quite loud - which disappears within 5-10 minutes, and does not recur until good and cold again. It also goes away with higher revs, but comes back around 1500 revs - until warm, when it vanishes completely.

The independent garage I use is convinced it's external (ie not within the block): they've used a stethoscope to try and track it down. So far they've replaced cambelt and tensioner, but the noise is still there, although it seems to go off even sooner now. They've established that it's not caused by anything driven by the ancillary belt (the one outside the timing belt cover, that drives the aircon compressor amongst other things), by running the car cold with that belt removed - noise still there. They say the water pump is fine.

They want to replace the crankshaft pulley now - sounds expensive to me!

Anyone any experience of this?

[Martin Cox]

Possibly the vacuum pump for the brake servo? They are known to do this.

[RoyMacDonald]

Possibly the vacuum pump for the brake servo? They are known to do this.

I had that with my 940TD. The garage took the pump off and ran the engine to check that the noise dissapeared. Mine went at 95,000 miles on the 940.

[vincentvg]

This is turning into quite a nightmare. All pulleys and tensioners have been replaced along with cambelt. Garage is adamant that it's not the vacuum pump (which I gather is at the opposite end of the block). Noise virtually disappeared after all their attention, but now seems to have come back, much quieter than before. They seem to think that it's something to do with the fit of the bottom pulley (big fat composite affair) on the crank. Does this seem feasible to anyone?

I haven't had a bill yet - dread to think what it will be - they've spent countless labour hours trying to track this down. Can't help wondering how much of what they've done has been necessary!

[pookie]

Carefully check that the rubber bonding on the crankshaft pulley is intact and has no cracks etc. Also ( and this is important ) check that the pulley that drives the cambelt doesn't have a worn keyway where it slides over the crankshaft. You will need to remove the cambelt to check this.

Pookie

[vincentvg]

Carefully check that the rubber bonding on the crankshaft pulley is intact and has no cracks etc. Also ( and this is important ) check that the pulley that drives the cambelt doesn't have a worn keyway where it slides over the crankshaft. You will need to remove the cambelt to check this.

PookieThanks Pookie. Yes, the old pulley had what appeared to be mild cracks in the rubber - very minor I should have thought. It's been replaced with a new (aftermarket) pulley. If there's any keyway wear now, it's either a badly machined pulley, or, presumably, wear in the crankshaft itself. Is that possible - at 67,000 miles?

[vincentvg]

Update for anyone else unfortunate to experience this: at last it's fixed! Appears to have been some sort of infinitesimal play between the cambelt pulley and keyway, and the crankshaft nose/key. Garage increased the clamping force by adding a shim between this pulley and the big fat ancillary pulley that bolts onto the end of it, and drives the accessory belt (1 shim is already standard apparently). So it seems they were in the right area (ie the whole bottom pulley assembly), but I probably didn't need the new bonded pulley. Hope this might help someone, someday.