Timing belt rattle

[alwigley]

Now that she is finally running, I thought I better go looking for the wierd rattle I have heard from the timing belt cover - had originally heard that the cam assembly bolt can work loose, but can detect no play in the camshaft having taking the distributor rotor off, however with the cam cover off and the engine running, it appears that the timing belt is bouncing up and down on approaching the camshaft sprocket, and the back of it is striking the plastic belt cover occaisionally. Noise seems to disappear when the engine has warmed up, so suspect the belt is a fraction too loose.

Anyone else had a similar issue ?

Cheers

 

[TTM]

Are you sure there isn't a roller or two missing?

 

[alwigley]

Seem to be all present and correct, will have to consult the diagram.......

 

[chrisg]

All I can suggest my limited technical knowledge, is that if the belt is slapping around so much that its creating a noise that you can hear/identify over the general engine noise:

You need to get it fixed ASAP before the belt jumps off or let's go and wrecks several of your inlet valves !

 

[macandsue]

We had a rattle.......and one mile later we had a dead engine, and a bill for over £1,000.
Beware!

Mac

 

[pauljmcnulty]

however with the cam cover off and the engine running, it appears that the timing belt is bouncing up and down on approaching the camshaft sprocket, and the back of it is striking the plastic belt cover occaisionally. Noise seems to disappear when the engine has warmed up, so suspect the belt is a fraction too loose.

Blimey, how was it tensioned? I'd be wary of starting it up until it's been properly checked out.

 

[Mike_Pollock]

Hi
Check the tightness of the crank pulley bolt - it should be stupidly tight! - I've seen a couple of engines with loose ones and producing a rattle.
One was loose for so long it enlarged the keyway by about 3 times - and the engine still ran!
Mike

 

[pauljmcnulty]

One was loose for so long it enlarged the keyway by about 3 times - and the engine still ran!

I've seen it, not to be recommended! []

 

[alwigley]

Suspect it has not been tensioned since the engine was rebuilt roughly 10,000 miles and 5 years ago...... will arrange to get it checked out locally and see what gives. Might take a look at the crank pulley bolt though. Have to say that when she's warm, there is no noise at all - checked it out when I got home tonight.

 

[sawood12]

The belt tension needs checking about 1500km after initial installation of a new belt and retensioning if necessary. I am staggered at the number of people and (so called) specialists who don't know this and don't recommend it and those who just ignore it because you don't have to do it on their Vauxhall Astra or because their mate or someone down the pub didn't bother and everything seems OK with his car. When I had the belts done on my car the tension was checked within the 1500km's and a retention was required.

The loss of tension could be due to this or maybe like you say, something has come loose or a bearing has broken down. Still sounds like you've caught it just in time, some people don't get a warning at all.

 

[pauljmcnulty]

Suspect it has not been tensioned since the engine was rebuilt roughly 10,000 miles and 5 years ago......

Are you saying the belt is 5 years old? They have an absolute maximum life of 4 years, and they do fail over that age. Not trying to be over dramatic, but I really wouldn't run the engine if the belt's over 4 years old and there are odd noises coming from it.

 

[alwigley]

Have only had the car for a couple of months and barely driven her because of the (now fixed) idling problems, and the servicing information since the engine rebuild is non-existent so have to assume they were last done in 2006. The belts look to be in very good condition, so will take it to a local specialist and see what he has to say. Thanks for all the advice.......

 

[sawood12]

I would heed Porsches replacement interval of 4yrs or 40kmiles. You cannot visually inspect these things and determine if they are good to go for further running. The specialist told me in his time he's seen belts that had failed that looked in great condition - no perishing or deterioration of the rubber. The strength of these things is not in the rubber - it is in the internal chords which degrade over use so the damage may all be internal. The mileage limit of 40k miles is to protect against the degradation of the internal chords through use and the 4 yr limit is to protect against time related degradation of the rubber which does degrade due to ozone and oxygen attack (ozone and oxygen is corrosive to rubber and causes hardening and cracking) and any chemical attack of the rubber due to any spillages of oils or other engine fluids.

Timing belts always seem to be the subject of some discussion - I don't see why they should be. The replacement intervals are clear and if heeded the timing belt is 100% reliable. And don't forget the balance shaft belt. Replace that at the same time to be safe. There is no service interval defined against these but when they fail they can sometimes take out the timing belt too.

 

[tref]

I would second Paul's advice... don't risk a wrecked engine... get it fixed now.

How-ever... there is one other thing I would check first, to ensure you don't do the belts and still have a rattle... The water pump. wobble the end of the pulley firmly. If you can detect any play, it is knackered, and can make a rattling noise. It is generally recomended to replace it at least every other belt change anyway. Expensive, I know... but... it will affect tension on the belts, and it will cause a very broken engine if it lets go.

They don't necessarily leak when they are knackered by the way!!!

Sorry if this is telling you something you already know.

Regards,

Tref.