Sudden big end noise?
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You need to be sure where the noise is coming from - top or bottom of the engine as other replies have said. A stuck valve can make you think you've got bottom end knocks as you get piston to valve noise and cam follower noise as a result. The fact it's only firing on three is suspicious but could be a red herring of course.
Nigel F.
Nigel F.
1970 S4SE/1760cc big valve/SA-AX block, L2s, 45DCOEs, 1978 Jensen GT, 1962 AH Sprite, Alfa-Romeo 159, 1966 Bristol Bus, 1947 AEC Regal bus.
- nigelrbfurness
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Thanks NigelF,
Managed to get a brief look this morning.
Sadly I cannot feel any exhaust leak
Pulled each plug lead in turn, no change in noise.and same drop in revs so assume that all cylinders are firing and from what I have read this rules out a big end problem.
Frequency at 1100 rpm is about 4 beats per second, I assume this narrows it down to one cylinder but with a stethoscope I cannot detect any difference between cylinders when listening at cam covers or various points on the head, block or sump.
Have not done loose crank test or removed cam cover yet, not enough time today.
Noise seems to be just as loud whether I listen at top of engine or under sump.
I have made 2 recordings but do not know whether I can post these?
Thanks for all the interest.
Managed to get a brief look this morning.
Sadly I cannot feel any exhaust leak
Pulled each plug lead in turn, no change in noise.and same drop in revs so assume that all cylinders are firing and from what I have read this rules out a big end problem.
Frequency at 1100 rpm is about 4 beats per second, I assume this narrows it down to one cylinder but with a stethoscope I cannot detect any difference between cylinders when listening at cam covers or various points on the head, block or sump.
Have not done loose crank test or removed cam cover yet, not enough time today.
Noise seems to be just as loud whether I listen at top of engine or under sump.
I have made 2 recordings but do not know whether I can post these?
Thanks for all the interest.
Elan S4 DHC 1970
Elan +2S 130/5 1973
Excel SA 1987
Elan +2S 130/5 1973
Excel SA 1987
- NIGELAN
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Dont know if its been mentioned but have you considered it may be a loose timing chain, if you dont want to remove the cam cover to check the adjustment, loosen the lock nut and turn in the adjuster slightly, you can usually hear the chain "whine" if it becomes too tight but then back it off slightly.
Brian
64 S2 Roadster
72 Sprint FHC
64 S2 Roadster
72 Sprint FHC
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types26/36 - Coveted Fifth Gear
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NIGELAN wrote: a nice simple fix (if true!)
Yes providing it is only routine adjustment ...........(a slack chain) could have other implications with the sprockets/idler gear etc. as there is a "school of thought" that say a chain does not stretch
.......good luck anyway.
Brian
64 S2 Roadster
72 Sprint FHC
64 S2 Roadster
72 Sprint FHC
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types26/36 - Coveted Fifth Gear
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A broken exhaust mount bracket on the back of the gearbox can produce alarming knocks and rattles which might appear to be engine/gearbox related. Check out this earlier post....
lotus-twincam-f39/help-identify-this-strange-noise-please-t40644.html
.... there is a video clip which might help you rule it out
lotus-twincam-f39/help-identify-this-strange-noise-please-t40644.html
.... there is a video clip which might help you rule it out
Roger
S4 DHC
S4 DHC
- oldelanman
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As can a loose alternator bracket, crank pulley etc.
It would help if the OP could confirm that he does indeed know and recognise the sound of big end bearing failure. TBH I have my doubts as he drove it 100m and has not mentioned low o?l pressure, if a big end is shot enough to be heard at tickover only someone with zero mechanical sympathy could bear to raise the revs and drive the vehicle unless it was life and death.
It would help if the OP could confirm that he does indeed know and recognise the sound of big end bearing failure. TBH I have my doubts as he drove it 100m and has not mentioned low o?l pressure, if a big end is shot enough to be heard at tickover only someone with zero mechanical sympathy could bear to raise the revs and drive the vehicle unless it was life and death.
- Chancer
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Chancer wrote:As can a loose alternator bracket, crank pulley etc.
It would help if the OP could confirm that he does indeed know and recognise the sound of big end bearing failure. TBH I have my doubts as he drove it 100m and has not mentioned low o?l pressure, if a big end is shot enough to be heard at tickover only someone with zero mechanical sympathy could bear to raise the revs and drive the vehicle unless it was life and death.
yes, the engine still running with oil pressure is what made me suggest to look into optimistic options... recordings of the noise may be of help, though I usually find it difficult to diagnose without facing the actual engine in the flesh.
S4SE 36/8198
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nmauduit - Coveted Fifth Gear
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Hi Chamcer, sorry should have replied to your earlier comment on "do I know what a big end sounds like" to which tne honest answer is "no". I did think I had said that the oil pressure is still very good.
Car was gently reversed back into garage at very low rpm after research on this forum seemed to indicate not a big end.
I did carry out some tests earlier today, see earlier posting, which seem to rule out big end.
Lots of things to check on monday, thanks.
Car was gently reversed back into garage at very low rpm after research on this forum seemed to indicate not a big end.
I did carry out some tests earlier today, see earlier posting, which seem to rule out big end.
Lots of things to check on monday, thanks.
Elan S4 DHC 1970
Elan +2S 130/5 1973
Excel SA 1987
Elan +2S 130/5 1973
Excel SA 1987
- NIGELAN
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Drop a valve? You can buy a camera the looks through a probe that you could look in the cylenders through the spark plug holes.
https://www.harborfreight.com/digital-i ... 61839.html
Mr.G
https://www.harborfreight.com/digital-i ... 61839.html
Mr.G
- Mr.Gale
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Mr.Gale wrote:Drop a valve? Mr.G
NIGELAN wrote: Pulled each plug lead in turn, no change in noise.and same drop in revs so assume that all cylinders are firing .
Unlikely to be a dropped valve if all cylinders are firing equally.
Brian
64 S2 Roadster
72 Sprint FHC
64 S2 Roadster
72 Sprint FHC
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types26/36 - Coveted Fifth Gear
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Okay.
I will check all ancillary possibilities tomorrow. Then timing chain, crankshaft movement and then off with the cam covers.
Will also try the YouTube suggestion - should be amusing!
Thanks again for all suggestions, very grateful.
Will report back.
I will check all ancillary possibilities tomorrow. Then timing chain, crankshaft movement and then off with the cam covers.
Will also try the YouTube suggestion - should be amusing!
Thanks again for all suggestions, very grateful.
Will report back.
Elan S4 DHC 1970
Elan +2S 130/5 1973
Excel SA 1987
Elan +2S 130/5 1973
Excel SA 1987
- NIGELAN
- First Gear
- Posts: 33
- Joined: 02 Aug 2012
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