Lotus Elan

Light rattle from engine

PostPost by: Davidb » Sat Apr 29, 2017 9:16 am

My engine is together and running finally. It sounds strong but there is a light rattle from the front. We have tried adjusting the timing chain tensioner-chain is new-but the noise is still there. Do the tensioners ever cause problems? I didn't replace any parts of the tensioner since it looked ok.
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PostPost by: miked » Sat Apr 29, 2017 12:02 pm

David, Have a read of this. May not be but worked for me. It is easy to distort the tension quadrant device when replacing the sprocket. mine was twisted. Quite hard to see.

lotus-twincam-f39/clacking-noise-tickover-t30840.html?hilit=lexan cam cover


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PostPost by: Davidb » Sat Apr 29, 2017 2:57 pm

Thanks for t hat Miked. I will check the sprocket carrier today.
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PostPost by: Davidb » Sun Apr 30, 2017 3:23 am

Today I stripped out the whole tensioner assembly and checked it-I did not find any problems. It is straight, there is no play in the tensioner sprocket and the 'washer' was on the end of the adjuster. I put it back together and could only run it briefly due to the location and could not test drive but it sounded better! I will run/drive it tomorrow hopefully and will report back.
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PostPost by: Concrete-crusher » Sun Apr 30, 2017 7:55 am

I had a similar noise and it turned out to the the fan blade rattling in the rivets.

Once I changed to an electric fan and removed the old fan it stopped.

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PostPost by: Davidb » Mon May 01, 2017 2:10 am

Steve: I don't have the original fan-I have an electric fan now so that was not the cause of the noise. I ran the car today and got it quite hot - the noise is very minor now-in my humble opinion-I think I will run it for a while and see if it changes.
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PostPost by: toomspj » Mon May 01, 2017 10:17 am

You might also check alternator / dynamo. I've had rattles from them in the past which took a while to find.
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PostPost by: billwill » Mon May 01, 2017 11:48 am

The sound of the cams contacting the followers can sound a bit like a rattle.
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PostPost by: JJDraper » Mon May 01, 2017 4:11 pm

Don't forget the vacuum NRV can also give a light ticking sound at low revs if you are really paranoid..

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PostPost by: Mick6186 » Mon May 01, 2017 4:48 pm

A 'dry' fan belt can make a rattle like a failing water pump bearing. Give the belt a quick squirt of WD40 with the engine running. If that's the problem it will stop rattling immediately,
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PostPost by: Robbie693 » Mon May 01, 2017 11:02 pm

My fan motor bearing was making a ticking noise until I upgraded but it sounds like yours is new...

A leaky exhaust manifold gasket can make a ticking noise too.

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PostPost by: 2cams70 » Mon May 01, 2017 11:57 pm

Run the engine for a VERY short time with the fan belt disconnected and see if that stops the noise. That will isolate alternator, fan and water pump as sources of the noise.
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PostPost by: Davidb » Tue May 02, 2017 4:33 am

Thanks for all the input everyone. I tried and eliminated all the points that were raised.
Personally I think it is OK. There is a light clatter from the engine which as Bill said is the cam lobes hitting the buckets. There is also a slight chain noise but nothing serious after further adjustment.
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