'Knocking' noise from engine?
Discussion
As per the title - I have a knocking/tapping noise from the engine when idling?
Seems to be located on the n/s of the engine (rocker cover area??)
Any advice as to the cause and/or a fix (simple please) for the noise/problem.
Also, seem to have a slight mis-fire when under load/accleration - any thoughts on locating/rectifying would be gratefully received.
As a footnote - this is the first time the engine has been run since September - anything to do with that?
Many thanks in advance.
Cheers
Jaye
Seems to be located on the n/s of the engine (rocker cover area??)
Any advice as to the cause and/or a fix (simple please) for the noise/problem.
Also, seem to have a slight mis-fire when under load/accleration - any thoughts on locating/rectifying would be gratefully received.
As a footnote - this is the first time the engine has been run since September - anything to do with that?
Many thanks in advance.
Cheers
Jaye
Hi Jaye.
As you have an S3, do you know if you have got hydraulic tappets? I have a 91 S3C which does but I understand not all have them. If so, you may just have a tappet which needs bleeding. Providing you have good oil pressure, run the engine at 1500 to 2000 rpm for 10 to 15 minutes, or until the noise stops. Job done.
With regards to a misfire, start with the basics, plug gaps, dissy cap etc. If your car has been stood you may just have condensation in the dissy cap, or something along those lines?
Stew.
As you have an S3, do you know if you have got hydraulic tappets? I have a 91 S3C which does but I understand not all have them. If so, you may just have a tappet which needs bleeding. Providing you have good oil pressure, run the engine at 1500 to 2000 rpm for 10 to 15 minutes, or until the noise stops. Job done.
With regards to a misfire, start with the basics, plug gaps, dissy cap etc. If your car has been stood you may just have condensation in the dissy cap, or something along those lines?
Stew.
Stew
Mine's a 1990 S3 - no idea if they are hydraulic tappets? How do I find out? Alos, have had the car out on a hour long run (over 2000 revs) and still 'tapping' when idling??
With regards to the misfire - the dizzy is fine (already checked) - could be the plugs though - anyone know what the gap should be??
Cheers
Jaye
Mine's a 1990 S3 - no idea if they are hydraulic tappets? How do I find out? Alos, have had the car out on a hour long run (over 2000 revs) and still 'tapping' when idling??
With regards to the misfire - the dizzy is fine (already checked) - could be the plugs though - anyone know what the gap should be??
Cheers
Jaye
you use the hose as a stethoscope (that's all a stethoscope is really) - stick one end in your ear'ole and move the other end about near exhaust gaskets etc till the noise is loudest - helps you isolate the noise source.
You can also use a 'ammer 'andle - press it against bits of the engine and you'll hear the internals working - helps you diagnose a loose tappet or rumbly bearing etc. Just don't put it near spark plugs - 30,000 volts through the brainbox can smart a bit.
You can also use a 'ammer 'andle - press it against bits of the engine and you'll hear the internals working - helps you diagnose a loose tappet or rumbly bearing etc. Just don't put it near spark plugs - 30,000 volts through the brainbox can smart a bit.
If you have had a good run then I would not think it is a tappet and would agree that a manifold gasket could be the cause, especially if you have had them off.
Silly question, but are you sure you have tightened all the nuts up? If it is an exhaust blow, you could get someone to place a rag over the tail pipes briefly, while on idle and listen to see if the noise changes under bonnet. If it does then you are on the right track. You would know if you found a blow using a hose to the ear as you would get a different sound compared to placing the pipe around part of the gasket which is not blowing. Think that makes sense?
With regards to plug gaps, I found 3 different settings when I was looking to replace mine depending on what info I was reading.
.024, .028 and .032 imperial.
My new plugs came pre gapped at .028 so I put them in at that. The engine really struggled to fire and would not tick over. I re gapped them at the larger .032 (about .8mm for you young boys)and it ran fine. I would not have thought that it would be such a dramatic change but it was and the old motor runs a treat now.
Hope this helps?
Stew.
Silly question, but are you sure you have tightened all the nuts up? If it is an exhaust blow, you could get someone to place a rag over the tail pipes briefly, while on idle and listen to see if the noise changes under bonnet. If it does then you are on the right track. You would know if you found a blow using a hose to the ear as you would get a different sound compared to placing the pipe around part of the gasket which is not blowing. Think that makes sense?
With regards to plug gaps, I found 3 different settings when I was looking to replace mine depending on what info I was reading.
.024, .028 and .032 imperial.
My new plugs came pre gapped at .028 so I put them in at that. The engine really struggled to fire and would not tick over. I re gapped them at the larger .032 (about .8mm for you young boys)and it ran fine. I would not have thought that it would be such a dramatic change but it was and the old motor runs a treat now.
Hope this helps?
Stew.
Stew Mc said:
If you have had a good run then I would not think it is a tappet and would agree that a manifold gasket could be the cause, especially if you have had them off.
Silly question, but are you sure you have tightened all the nuts up? If it is an exhaust blow, you could get someone to place a rag over the tail pipes briefly, while on idle and listen to see if the noise changes under bonnet. If it does then you are on the right track. You would know if you found a blow using a hose to the ear as you would get a different sound compared to placing the pipe around part of the gasket which is not blowing. Think that makes sense?
With regards to plug gaps, I found 3 different settings when I was looking to replace mine depending on what info I was reading.
.024, .028 and .032 imperial.
My new plugs came pre gapped at .028 so I put them in at that. The engine really struggled to fire and would not tick over. I re gapped them at the larger .032 (about .8mm for you young boys)and it ran fine. I would not have thought that it would be such a dramatic change but it was and the old motor runs a treat now.
Hope this helps?
Stew.
Good point - I found before that the plug gaps can make a big difference, and 0.8 / 0.9 seems about right.Silly question, but are you sure you have tightened all the nuts up? If it is an exhaust blow, you could get someone to place a rag over the tail pipes briefly, while on idle and listen to see if the noise changes under bonnet. If it does then you are on the right track. You would know if you found a blow using a hose to the ear as you would get a different sound compared to placing the pipe around part of the gasket which is not blowing. Think that makes sense?
With regards to plug gaps, I found 3 different settings when I was looking to replace mine depending on what info I was reading.
.024, .028 and .032 imperial.
My new plugs came pre gapped at .028 so I put them in at that. The engine really struggled to fire and would not tick over. I re gapped them at the larger .032 (about .8mm for you young boys)and it ran fine. I would not have thought that it would be such a dramatic change but it was and the old motor runs a treat now.
Hope this helps?
Stew.
Jaye R said:
Also, seem to have a slight mis-fire when under load/accleration - any thoughts on locating/rectifying would be gratefully received.
As a footnote - this is the first time the engine has been run since September - anything to do with that?
Cheers
Jaye
Dont forget Jaye that you will need to take the engine through a few hot and cold cycles before she runs smooth even with all the correct settings...As a footnote - this is the first time the engine has been run since September - anything to do with that?
Cheers
Jaye
are you going to be around tues/wed evening this week ?
K
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