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Discussion Starter #1
immediately after an unnecessary and unmatched downshift on track (but probably not an over-rev technically speaking - judging by a video which doesn't show revs going above 8500) i got extremely loud ticking which is synchronized with engine speed. i pulled over and shut the engine off. had the car towed home. no check-engine light. car is drivable and idles fine (based on another minute of running i was able to bear).

the ticking sounded valve related, especially remembering all the stories about broken rockers and warn camshafts (a related link listed here), so i took the valve cover off the other day.

http://www.lotustalk.com/forums/f25/camshaft-cover-defect-causing-rocker-arm-breakage-p1302-50594/index9.html

as these 5 pictures here show (the remaining 3 look similar), everything looks good under there to me: no wear on camshafts that i can see, all the rocker arms are in one piece.

i was able to rotate the engine to take a look on all sides of the camshaft, by turning one of the rear wheels (spark plugs out, trans in first). a slightly strange thing was that difficulty in turning was not smooth - i would struggle, than there would be a burst of easy motion, than struggle again, and so on. maybe that makes sense with the different pumping resistance from the engine at different parts of the cycle; maybe.

but then the truly strange thing was that after some point i could not turn the engine anymore this way, no matter how hard i tried. it seemed like something was blocking it at that point.

my theory is that i have one or more bent valves which are not moving properly anymore and are hitting the piston. this would be creating the ticking noise. and in my turning by hand i might have reached this interference point so that i can't turn it by hand anymore.

based on that, i should take the head off and inspect the valves and tops of pistons.

my questions are:
- any better theories?
- is what i have described worth the pain of removing the head to see what is actually going on?
- if so, could somebody point me to any discussions related to that work that would be a good supplement to the toyota engine manual?
- anything else i should be looking into here to diagnose this?
 

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before you go yanking the head off, you need to do a compression test...
 

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Without hearing the sound its hard to know what direction to point you in. do you have any excessive cam chain movement? I have seen tensioners fail. could cause noise but maybe not a consistent rhytmic tick.
 

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I am not sure how the RPM signal works (I.e. straight iff the crank or some relationship to the spark.) the engine would stop sparking past 8500.if the sounds were 1/2 engine you would know for sure.
A Compression test might be good. Or a leak down test.
Depends on whether the valves are bent enough to not bend back and seal.
Often they do but the flexing makes the heads pop off after a while.
Or a borescope, or taking the cams out and the springs to see if the valves move bound.

But you have the causal mechanism, which was the buzzed engine.
And you have the noise, so you know it is not healthy.
Therefore... pulling it out before you have a pipe of scrap make more sense than trying to see how it goes and hoping.
 

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Discussion Starter #6
Without hearing the sound its hard to know what direction to point you in. do you have any excessive cam chain movement? I have seen tensioners fail. could cause noise but maybe not a consistent rhytmic tick.
The sound is very easy to describe in words: it is perfectly regular crisp metallic ticking (annoyngly loud and obviously not normal) that is synchronized with the engine speed (speeds up when the engine speeds up). I wish i had counted its frequency - i will go back to the video - maybe i can hear it there - but it is somewhere between once
every couple of revolutions and couple of times per revolution.

I didn't feel the chain - will do that - but it looked tight.
 

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Discussion Starter #7
I will do a compression test or leak down test and report back.

Thanks for the direction all.
 

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I will do a compression test or leak down test and report back.

Thanks for the direction all.
No need for a leak down test, they are PIA to perform, and at this point nothing to be gained.
If you've a bent valve in there, you will have zero or extremely low compression in that cylinder.
The leak down test will tell you if your low compression is due to ring or valve leakage.
Rings don't make a clicking noise when bad...
If the compression test shows bad compression, you can then check valve clearances to isolate the bad valve(s) (as the clearance will be very high), but that hardly matters as the head is coming off anyway at that point...

Ideally you perform a compression check with the motor at temp so the rings are expanded.
In any case be sure to remove the fuel pump fuse prior to testing so you're not dumping raw fuel into the cylinders...
 

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I would not warm the engine up to do a test.
And if the engine is binding, I am not sure would start it up as you already have identified the buzzing mechanism. Just get stuck into getting the head off while it and the pistons are most likely sound.

The rods can fail due to the buzzing.
Whether they magnaflux them. or how exactly they are tested I am not sure... But test them.
 

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The sound is very easy to describe in words: it is perfectly regular crisp metallic ticking (annoyngly loud and obviously not normal) that is synchronized with the engine speed (speeds up when the engine speeds up). I wish i had counted its frequency - i will go back to the video - maybe i can hear it there - but it is somewhere between once
every couple of revolutions and couple of times per revolution.

I didn't feel the chain - will do that - but it looked tight.
Sounds silly, but it wouldn't be the spark plugs would it? My car had the exact same sound (in addition to misfiring when I really got on the throttle) and ended up being the white ceramic part of the spark plug somehow loosened and caused it to wiggle and make a metallic ticking noise
 

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Discussion Starter #18
Mine started to sound like that after oil line failure. And the dealer said it sounds normal to them. I will have to open it up and see what's going on.
Sometimes it is hard to judge the relative sound level from a recording, so i cant be sure how loud yours is, but no sane person would call my noise normal.
 

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Discussion Starter #20
Sounds silly, but it wouldn't be the spark plugs would it? My car had the exact same sound (in addition to misfiring when I really got on the throttle) and ended up being the white ceramic part of the spark plug somehow loosened and caused it to wiggle and make a metallic ticking noise
None of my plugs has fallen apart. Although some of them have become covered with copper colored dust.
 
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