| Author | Message | ||
     John G. Frequent User Username: john116 Post Number: 60 Registered: 4-2012 |
My SSII engine has developed a rather loud knock while running, especially at idle. It seems to improve at faster engine speeds. As part of my attempts to diagnose what it is, I've found that removing a spark plug lead doesn't change the noise, although I also found spark plug not firing (probably a separate issue). Also, the loudness of the knock changes with ignition timing adjustment. It gets louder with retarded ignition. It's hard to tell where the noise is coming from, but I think it's the upper part of the engine, on the drivers (RH) side of the engine. At first I thought it was a noisy tappet, but now am not sure (although it could still be that). I know long distance diagnosis is difficult, but any suggestions gratefully accepted. John | ||
| ross kowalski Grand Master Username: cdfpw Post Number: 533 Registered: 11-2015 |
John G, That isn't quite enough information there to make a diagnosis with any degree of certainty. You could isolate where the knock is coming from with a piece of pipe or hose placed against the ear and against various parts of the engine until the offending area is located. If the knock is so loud that you are concerned about running the engine at all, a static inspection of things like the valve train or the crank pulley might be in order. On the plus side, that engine is so quite that locating the knock shouldn't be too bad a job. Regarding the plug not firing, if you pulled a lead and it didn't change the engine rpm, that is what we refer to as a dead cylinder, it can be a plug that is not firing, but also a stuck valve, a holed piston, a broken rocker arm, etc. It could very much be related to the noise. | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 1847 Registered: 6-2006 |
Does it sound like a sharp tap or a tock (more hollow sounding?) Use the dipstick to listen to pumps etc. (That's the engine oil dipstick . .not the power steering pump dipstick :D ) | ||
| John G. Frequent User Username: john116 Post Number: 61 Registered: 4-2012 |
Thanks for the suggestions. It's not so bad that I don't think I can run the engine, but it's not good either. It sounds like a sharp tap. Hard to describe. Also, not sure why ignition timing variance increases or decreases the knock noise. | ||
| Geoff Wootton Grand Master Username: dounraey Post Number: 1771 Registered: 5-2012 |
Hi John Check it's not coming from the hydraulic pumps, situated on the top front and rear of the engine. Geoff PS - Just realized I'm repeating Paul's suggestion. I like the idea of using the dipstick as a stethoscope. | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 1492 Registered: 9-2004 |
Noise high up or low on the engine? Noise variation with ign timing in most cases points to piston or big end failings, has the oil light come on at all when running or on idle? Has the car suffered any boiling or running hot probs in the past. Driven till it stops!!!!!!!!!!!!!!!! If all ok on that front then as Ross suggested the crank pulley could be failing also have known a flexi plate to make odd noise when failing! | ||
| John G. Frequent User Username: john116 Post Number: 62 Registered: 4-2012 |
Sounds highish up, but not right up top. Oil light not on at idle. Hasn't suffered any overheating issues in my ownership (last 6 years). Does it without the hydraulic pumps installed. | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 1848 Registered: 6-2006 |
Fix the spark plug not firing first. Check compression and valves operating on that cylinder. Check for bent pushrods. | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 1493 Registered: 9-2004 |
To check piston or position of noise I find a solid screw driver best as it transmits well with shock resonation. Use on exhaust manifold cylinder porting to confirm piston, if at fault.  | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 1494 Registered: 9-2004 |
Compression "down" on cylinder confirmed by king lead disconnected and engine turning with starter motor showing uneven cranking! | ||
| ross kowalski Grand Master Username: cdfpw Post Number: 538 Registered: 11-2015 |
John, If you do what Patrick L suggested and filmed it, it would be a pretty good diagnostic. I could only find this example of a dead cylinder crank sound on youtube, it's not so good, but you get the idea. https://youtu.be/pIkzXdLuKmc?t=154 | ||
| ross kowalski Grand Master Username: cdfpw Post Number: 539 Registered: 11-2015 |
John, Here's a better video of the sound of a dead cylinder on crank. The guy is doing some sort of compression too, but the sound pretty much says dead hole as Patrick L was saying. https://youtu.be/WKdZsWU2ZmI?t=241 | ||
| John G. Frequent User Username: john116 Post Number: 63 Registered: 4-2012 |
Ross/Patrick - will try and upload a video of engine running soon. | ||
| Mark Aldridge Grand Master Username: mark_aldridge Post Number: 454 Registered: 10-2008 |
A crude compression test is to remove all sparkplugs, disconnect the king lead and place a finger over each plug hole in turn, whilst someone operates the starter. this will identify a major problem. Mark |
