rodgling
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| posted on 17/4/12 at 10:23 PM |
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diagnose my engine rattle
The short of it is, my engine sounds like this:
http://www.youtube.com/watch?v=j5VNSIUZQSg
http://www.youtube.com/watch?v=fXxcptTmSqI
Last week I changed the oil and did a track day, half way through the track day I noticed this. I don't think I over-revved it (maybe once very
slightly with engine braking), definitely didn't starve it of oil. Loads of oil pressure still.
Under the rocker cover looks healthy, no play anywhere. I can't locate the sound very precisely. I've disconnected each spark plug in turn
and found no improvement. Removing the belt with no improvement rules out water pump, alternator etc. Knock sensors don't report a problem.
Driving at 50 mph I found that the sound went away with no throttle, the slightest bit of throttle and it came back. It's present if I just
tickle the throttle up to say a steady 1500 rpm sat in the garage (so no load).
I've ordered a new timing chain tensioner in the hope that it's just a loose timing chain, any other suggestions or things I can look
at?
[Edited on 17/4/12 by rodgling]
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Chippy
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| posted on 17/4/12 at 10:33 PM |
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Sounds like an engine strip to me, I wouldnt be happy with that. Could be a bearing of some sort, (small end). Does that engine have hyro tappets,
could be one of those. You should be able to locate the noise with a piece of broom handle, used as a stethescope. HTH Ray
To make a car go faster, just add lightness. Colin Chapman - OR - fit a bigger engine. Chippy
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rodgling
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| posted on 17/4/12 at 10:35 PM |
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I'm not happy with it :-( Solid shims, no hydraulic tappets. I've tried locating the noise with a screwdriver as a stethoscope, no joy so
far.
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old_timbo
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| posted on 17/4/12 at 10:37 PM |
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Have you checked for a exhaust manifold to head leak? Can get a strange ticking noise like yours from these.
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Volvorsport
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| posted on 17/4/12 at 11:00 PM |
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hmmm , without even listening to it , if its not an exhaust leak , under load - its the big ends .
not saying its that , but in general big ends
i once stripped a diesel toyota that had good oil pressure , couldnt pin point it at all apart from the rattle under load - the bearing collapsed ,
piston was hitting the cylinder head aswell !!!!
www.dbsmotorsport.co.uk
getting dirty under a bus
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rodgling
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| posted on 17/4/12 at 11:12 PM |
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Forgot to mention, it had new big end bearings fitted just before I bought it, maybe 1k miles ago. I'd hope they're still OK. Presumably
if a bearing has gone I can expect to find evidence in the oil?
The rattle sounds to me like it's about 6 Hz at idle, which is approximately every other revolution, makes me think/hope it's something in
the head and not a bearing? I'd expect a bearing noise to be every revolution?
[Edited on 17/4/12 by rodgling]
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Volvorsport
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| posted on 17/4/12 at 11:23 PM |
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depends on the ignition events , but ive listened and it does seem mechanical .
can you get at the sump easy ? it might have spun a bearing too , i dont think its piston slap either ..
www.dbsmotorsport.co.uk
getting dirty under a bus
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rodgling
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| posted on 17/4/12 at 11:41 PM |
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quote:
Originally posted by Volvorsport
can you get at the sump easy ? it might have spun a bearing too , i dont think its piston slap either ..
For some value of "easy". I took it off a few weeks ago doing the oil change to change a leaky gasket, it's a hateful job but it can
be done with the engine in the car.
What would I be looking for with sump off? What's a good next step to diagnose this?
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Volvorsport
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| posted on 17/4/12 at 11:52 PM |
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well , with access to big ends you should be able to spot a massive amount of play in one compared with the others if it is that , as long as its
nothing too obvious , youve got nothing too lose....
you cant really diagnose them properly without taking it apart sadly .....
www.dbsmotorsport.co.uk
getting dirty under a bus
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rodgling
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| posted on 17/4/12 at 11:56 PM |
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I guess it's sump off if a new chain tensioner (I've ordered one as it's potentially a cheap and easy fix, so it's worth a
shout) doesn't help then. What a pain.
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omega 24 v6
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| posted on 18/4/12 at 07:05 AM |
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Sounds strange. Almost like it half engine speed so my guess would be cam related.
If it looks wrong it probably is wrong.
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adithorp
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| posted on 18/4/12 at 07:47 AM |
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Difficult to say without hearing it in person... but sounds like big end bearing.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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franky
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| posted on 18/4/12 at 08:11 AM |
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Does sound strange dave, does the sound go at all at any rpm? you can get a cheap Stethoscope off ebay for a couple of quid. I'd hate to hear
its bearing related. get stethoscope and then try and locate where you think its coming from. could it be the vanos slipping at the front of the
engine?
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rodgling
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| posted on 18/4/12 at 09:16 AM |
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It's present at all rpm as far as I know. I'm going to borrow a stethoscope and try to locate it. I hope it's vanos or timing chain,
bearings would be bad. I saw some heavy misfires on track which makes me think vanos.
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hughpinder
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| posted on 18/4/12 at 09:53 AM |
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Happens under load at 'cam speed' - valve not seating/sticking partly open?
hugh
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Daddylonglegs
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| posted on 18/4/12 at 10:50 AM |
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Doesn't sound 'deep' enough to be a big-end to me. What about an injector? I've heard them make some wierd noises in the past
(assuming it's the type with solenoid)?
Just my 2p worth.
It looks like the Midget is winning at the moment......
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JAMSTER
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| posted on 18/4/12 at 12:42 PM |
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cam timing/vanos unit fault i've had smaller bmws making that sort of noise and it been down to eccentric shafts not sure if your engine has
these but might be worth a look
http://tis.spaghetticoder.org/s/view.pl?1/01/07/23
[Edited on 18/4/12 by JAMSTER]
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MikeRJ
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| posted on 18/4/12 at 01:01 PM |
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Vanos is not usually a low frequency intermittent rattle like that, it's more of a continuous clatter.
The seems to be idling quite roughly as well, have you checked the spark plugs? A loose plug can make a similar sort of noise.
[Edited on 18/4/12 by MikeRJ]
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hughpinder
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| posted on 18/4/12 at 02:00 PM |
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I like the spark plug idea - I've had that with a defective plug that was blowing and it did sound a lot like that.
Regards
Hugh
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rodgling
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| posted on 18/4/12 at 04:35 PM |
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Not a spark plug, I've checked those. Could be vanos - I've been getting misfires and very bad emissions which could both be explained by
wrong timing, but I'd like to be sure before I go down that road (it's expensive and I'd hate to go there and then discover I need a
new block due to spun bearings). Could be timing chain?
It happens mainly not under load, either with the car in neutral and a tiny bit of throttle, or when on the throttle gently cruising. I've yet
to hear it (maybe the occasional noise, but never a proper rattle) with no throttle. It's obvious on constant throttle and on over-run.
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Oddified
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| posted on 18/4/12 at 05:06 PM |
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From the sound and the discription of events, i'd guess at a little end.
Ian
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rodgling
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| posted on 18/4/12 at 06:04 PM |
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It looks a lot like a bearing has died. My (week-old) oil is full of what looks like glitter. I don't see any other interpretation?
Sump off tomorrow to try and figure out which one and if the engine is salvageable.
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rodgling
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| posted on 19/4/12 at 04:01 PM |
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Didn't get the sump off but had a poke under the rocker cover again. Valve clearance is way out, .279-.305 mm on the exhaust side (except one
just out of spec at .254) which is OK, but all bar two are .279 - .305 on the intake side too which is supposed to be at .18 - .23!
Doesn't explain the mess in my oil but it's another thing that needs sorting.
Cams look a bit worn, but I don't know how worn is too worn?
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