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k series cam belt noise


Julian H

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Hi

I am getting increasingly concerned, and deafened by a whirring / rubbing noise from my cambelt area. It is quiet for the first few minutes but slowly gets louder as the engine warms up. 

It is not really a whirring or rubbing noise, its sort of a belt noise. I wonder, is this a common / known problem, what is the most likely source. Could it be the tensioner bearings? The belt itself? 

The tension is correct, the belt appears in perfect condition, does not appear to be fouling anything and was only replaced last year [less than 1000miles ago :-o]

Appreciate some wisdom please.

Thanks,

Julian

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To be honest, there's not much in the area of the timing belt to make noise - as above, tensioner bearing, grumbling water pump, belt rubbing.  Alternator belt could be rubbing on the cover.  Your best to run without with the cover and investigate with a long screwdriver for noises, taking care not to drop it of course!   

 

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Try pushing the top of the plastic cam cover casing back towards the engine block. Many years ago my cover slightly eased away from the block causing the inside back to gently rub on the pulley giving a slapping sound.

CamBeltCover.thumb.png.0a1c3d1b8c93a7c79455525f87a8fb69.png

I tried flexing the cover back but once warm/hot it would flex away from the block again.

I've simply attached a bungie cord to the cover top bolt hole and pulled it around the breather pipe. No one has ever mentioned it (or not noticed) but it's been like this now for 10+ years. cheap fix *whistle*

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  • 2 weeks later...

Hi gents

I have now had a chance to look at my engine. I don't think I am any closer to sorting this.

I ran the engine without the cam belt front cover fitted [was a bit nervous about doing this even just sitting on the drive]. The belt is not rubbing on anything, the noise does not appear to be coming from anywhere specific, it is not the alternator or alternator belt though. I tried the "holding" a big screwdriver on various places and seeing if it would help me identify the noise source but it was generally too noisy to help in this instance.

The belt is in good condition too. It appears I have the correct cambelt [a Gates HTD5416XS]  and the tension seems right. One thing that slightly surprised me was the belt squeaked when flexed down between the two cam pulleys, Is this normal?

I recorded the squeaking noise and also the noise of the whirring when the engine is running, which I could email to anyone who may be able to help?

Thanks,

Julian

 

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No need to fret about running without the belt cover fitted, nothing's going to happen unless you start throwing gravel at the front of the engine (don't do that).

What makes you so sure the alternator/belt isn't the source, did you remove it?

I wouldn't expect there to be any appreciable slack between the two cam pulleys.  Maybe what you heard squeak when you did that was the belt tensioner.

Happy to have a listen although I wouldn't expect to be able to pinpoint the noise from a recording.  PM inbound.

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Here is a link to where Revilla explains the correct belt tensioning technique fitting the tensioner spring temporarily. Just in case you want to check it.

https://www.lotus7.club/forum/techtalk/k-series-cambelt-tension
 

I think I mentioned previously I had over tightened mine on one occasion and was advised its likely to 'sing' a bit! 
 

Regards

Ian

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Hi Julian I know this might sound a bit of a red herring but I have come across an inlet manifold gasket causing a similar sound to a squeaking cam belt. Spent an absolute age try to find the noise. It had no apparent running issues and really seemed to be belt related. Just a thought to consider.

Kind regards

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Hi thanks for the new suggestions. 

Hi Colin/Andy, I'm pretty sure its not that the squeak is when the engine is off and directly comes from the cambelt.

Stu, I have a manual tensioner, about 5mm flex of the cambelt between the cam pulleys.

The noise comes from the belt itself, running round the cam pulleys/crank/pump etc. I think I am just going to replace the belt and tensioner...?

Ian, I have previously found the correct method posted by Revilla, my engine is a DVA modified non-VVC, it does not have the threaded fixing point for the manual tensioner kit. Sadly I realised this after I have bought the kit.. :-o

Photo...

xlarge_IMG_0926.jpg.387c1c4bb6b16d45dc16eaceb14c051d.jpg

Thanks so much for the support, it is good to know I am not mad [i think]

Julian

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Hi Julian,

I've listened to the recordings.

Considering you were only running it up to 2500rpm that's a very high pitched whine. The only thing I can thing it could relate to would be the teeth on the belt itself. I can't thing of anything else operating at that sort of frequency.

What brand of belt have you used? Just wondering if it's a poor quality pattern part and the tooth profile isn't a very good match to the pulleys, so you get a sound of each tooth engaging the belt?

I've got an engine in the garage with a new Gates Powergrip belt but no belt cover (temporarily trial fitted to turn the engine over). I've just been out and pulled, prodded and twisted it and I can't make anything squeak like in your recording.

I do suspect that the noise is coming from the belt itself as it passes over the pulley teeth. If I were you I would swap the belt for a Gates Powergrip and see if it improves.

Andrew

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Hi Andy

Thanks for your reply and checking my recordings and your spare engine.

I too am pretty sure the noise is from the belt itself. I wonder if it is slightly faulty or contaminated. It is a Gates Powergrip.

I am going to replace it. Is it good practice to replace the [manual] tensioner too?

Julian

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