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[Brynjaminjones]

I've just started up the XJ to make sure all is okay, and I thought I'd look into a new noise it's been making since all of the work I've done on it.

There's a grating kind of noise coming from the front of the engine that is proportional to engine speed. It has done this since the first start up after new water pump, radiator, fan belt etc.
It doesn't make this noise at all with the belt off at all, but the pulleys also all feel fine when turned by hand (including the new water pump).

I thought that this could be the noise previously mentioned of the water pump pulley contacting the pump, but again, I can't feel this with the belt off.

I also noticed that the harmonic balancer seems to wobble slightly, but surely if that was the problem the noise would exist without the belt?

The noise is a constant grating/scraping kind of noise.

[Delk]

The bearing in the idler pulley fail at times and make noise. Mine did it for quite awhile with out causing a problem until I swapped the pulley.

I have also heard of the dampers failing at the rubber between the belt drive and hub. I have never seen one wobble at all.

[Brynjaminjones]

I'm familiar with the failing idlers - one left me stranded once and I've replaced another one too. I guess they're worth checking again though.


The damper actually looks okay to me when stationary - apparently if it's failed then the two metal components won't be sitting flush with each other. It seems to pretty definitely be wobbling though, although it doesn't look like it's wobbling in and out.


Is it possible that overtightening the belt could cause this noise? I figured that if this was to do with the wobbling damper, the noise wouldn't be a constant one.

[JamesH]

My harmonic damper failed and threw the belt off - they do go. A new one from Lighthouse and some garage labour might be worthwhile as preventative maintenance.

Not sure about the noise though, I'd say grumbling pulley but you've changed most of them haven't you?

[Dave69]

take belt off start engine and see if noise is still there, should be able to run it long enough to confirm its belt related

[Brynjaminjones]

Right, I've had a play...

Belt off and the noise is totally gone. The harmonic balancer is still wobbling just the same, so even if that is knackered, it's not what's making the noise!

One of the new idler pulleys actually doesn't seem that smooth, so I now suspect that is the cause of the noise! It looks to me like it might have corroded, possibly caused by having old coolant and water poured over it when I changed the rad/water pump/thermostat and hosed out the system, then didn't start the car for a month.

[Dave69]

id be surprised if the coolant has caused that damage after a month, seriously cheap part then???

get a long screwdriver or stethascope and touch the pulleys while having your ear on the other end. you will be able to hear the sound of a smooth pulley and then compare to the others for the one that has a rumble which should be the problem.

Obviously be aware of moving parts and fan while doing this, normally there shouldn't be any movement in pulleys or rough feeling when you spin a wheel

[Brynjaminjones]

I'm pretty confident it is that. I wouldn't have thought it would corrode that quickly either - it's only been on there about a year, but the noise only started after all the work I did. I think it was a Crown part.
Anyway, it's pretty definitely making noise when turned by hand, so when at engine speed I'm confident that it's the culprit!

[JamesH]

Crown parts can be poor quality sometimes