Lotus Elan

Slight engine knock S4 SE

PostPost by: 2tmike » Mon Jul 13, 2020 10:45 am

This has been with me ever since my ownership. It's noticable on tickover and again comes in a 2000rpm when driving (assuming its the same knock !!!) The engine is in generally good shape and the PO fitted new mains and big ends about 2000 miles ago after having the crank and bores checked and found in tolerance. At the same time the head was reconditioned by a reputable machine shop and looking at the receipts a new chain and tensioner were fitted in the rebuild. Oil pressure is good and only a puff of smoke on startup after standing for a week or two.
Going around the engine with a listening stick, the knocking seems to originate from the timing chain tensioner. If this is the culprit will I learn anything from removing the tensioner, spring etc from the side of the engine or does the cam cover need to come off to check - which would be sad since I've only just stopped it leaking oil ...:((
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PostPost by: sprintsoft » Mon Jul 13, 2020 1:01 pm

Hello Mike,

given that the noise originates around the timing case did you try the tensioner adjustment to see if it affects the noise?

It is likely after 2000 miles of use the chain tension will have become slightly loose and needs tightening.a little.

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PostPost by: 2tmike » Mon Jul 13, 2020 5:18 pm

Hi Ian,
No I haven't but will in the morning....I guess the cam cover will have to come off now....
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PostPost by: sprintsoft » Mon Jul 13, 2020 6:58 pm

No need to take the top off just yet, just try a small adjustment and see if it affects the noise. I would try a half turn in on the adjuster and note any change.

As a guide if the chain begins to whine it’s too tight, equally if it’s very loose it can rattle or tap on the top of the cam cover.
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PostPost by: 2tmike » Mon Jul 13, 2020 7:04 pm

Sounds a very sensible approach, first job tomorrow....
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PostPost by: 2tmike » Tue Jul 14, 2020 9:55 am

Well it took more than 1/2 a turn but the noise on tickover has mostly gone by increasing the chain tension. Either the chain had stretched quite a bit or it was adjusted to be very loose in the first place. The first couple of turns on the adjuster didn't have any resistance and two or three more got rid of the knock. I'm not sure what the over- tensioned 'whine' sounds like so for peace of mind I'll have the cam cover off later and measure the chain deflection. Thanks for the help !!
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PostPost by: 69S4 » Tue Jul 14, 2020 12:57 pm

The whine is quite noticeable if you tighten it up. The chain deflection method has always given me a chain that clatters if I adjust it that way. For decades now I’ve done it by the ‘find the whine and clatter points and set it half way’ method and that’s never caused any problems.
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PostPost by: sprintsoft » Tue Jul 14, 2020 1:10 pm

+1

measuring the 1/2" per the workshop manual is a rough guide only, the fine tuning is done by ear (excerpt below) - crude but effective!

Chain tension.jpg and
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