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  #46  
Old 08-12-2012, 04:43 PM
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smoke gets in your eyes
 
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Quote:
Originally Posted by Oldschoolgwin View Post
1.Does anyone think this is a connector rod?
A bent connecting rod such as afflicts 3.5s doesn't make noise.

Quote:
Originally Posted by Oldschoolgwin View Post
2. How about a crank bearing (though i think less chance since noirse sounds in the upper area - though could be misleading)
Bearing knock gets louder under load. Put the car in drive, plant your foot on the brake pedal and apply throttle. If the sounds gets louder, it could be a bad bearing.

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Originally Posted by Oldschoolgwin View Post
3. Piston slap?
I don't know what that sounds like but you'd trail clouds of smoke if the piston rings were bad. It'd probably be more difficult to start the engine, too. Weren't you planning a compression test? Do it cold for reference.

Sixto
87 300D^2

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  #47  
Old 08-13-2012, 12:51 AM
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I also recommend having a 17mm wrench or two at the ready to crack injection lines should you have a runaway condition after initial start.

Sincerely,

PE
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189K miles, Tachometer mod, cool wooden shift knob from PeachParts, CocoMats, Original factory paint, manual windows, manual sunroof. Starting to add AudioWrap to this car too!
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  #48  
Old 08-13-2012, 01:35 AM
Oldschoolbenz
 
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Latest results:

1. Belt tensioner dampener.
Pushed on this between the engin and dampening body to load up the ends - it did not reduce the knock sound. It did eliminate some very minor noise coming from it though.

This is not the issue.
2. Bad crank bearing question:
Drove the car up the street to load the engine - no change in noise intensity. Held brakes - loaded the engine pretty good - no change in noise.
So maybe this rules out the lower end.

3. Boroscope inspection - abort based on geometry of engine.

4. Lifter inspection - not done yet.
Maybe the lifter inspection by pushing on them. But would a completely collapsed lifter produce this much noise?
Not sure where to go from here - guess I'll think on it for a while.
Any more ideas?

I think we should had a "what's that noise library" with confirmed issue that caused it
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  #49  
Old 08-13-2012, 02:22 AM
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a "what's that noise library" would be a fabulous idea!
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  #50  
Old 08-26-2012, 01:49 AM
Oldschoolbenz
 
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Update:

1. Completely removed injector lines while running - to rule out dribble - no change - so give up on fuel causing knock from a leaking injector

2. Checked hydraulic lifters by removal of valve cover and pushing on them with a 1/4" wood dowl - unable to get any to budge (collapse), applied a good 15lb load on them, all seem to be in tight contact with the cam.

3. Listened for noise with stethoscope while engine turned over with socket on crank - no noise heard at all.

4. Close inspection of the video's, slowed down, shows the tap is twice per engine revolution. This would be a factual clue

5. PO says he never heard any knock, now he does have bad ears, so either he can't hear or perhaps my minor rotation of the engine backwards did damage something causing this noise.

Any thoughts on #4 / #5?

I'm really at a loss for now , though never giving up

Last edited by Oldschoolgwin; 08-26-2012 at 03:58 PM.
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  #51  
Old 08-26-2012, 02:31 AM
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Once per engine rev diminishes the likelihood of valvetrain and ignition causes. Does the knock get louder if you rev in drive while resisting with the brakes; i.e. put the engine under load?

Sixto
87 300D
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  #52  
Old 08-26-2012, 11:40 AM
Oldschoolbenz
 
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Quote:
Originally Posted by sixto View Post
Once per engine rev diminishes the likelihood of valvetrain and ignition causes. Does the knock get louder if you rev in drive while resisting with the brakes; i.e. put the engine under load?

Sixto
87 300D
Noise is once per two revolution. Sorry about that, i wrote it incorrectly.

Did the load test - no change in tone or loudness.

Last edited by Oldschoolgwin; 08-26-2012 at 03:59 PM.
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  #53  
Old 08-26-2012, 12:04 PM
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You are going to have to pull the rocker cover and check for a wiped cam lobe or something broken/loose.
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  #54  
Old 08-26-2012, 01:16 PM
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If its hydraulic lifters at fault you will tend to have a noisey top noise at the valve cover area.Ive owned some 190ds with the 2.5 diesel ,it was a similiar noise and just lived with it ,yours sounds a bit worse though from the video feed you made avail. ,it maybe because of the long sit.Try letting her idle 30 minutes a day for a few days in a row to see if it clears up .Are you getting any smoke out the back?

Last edited by chasinthesun; 08-26-2012 at 01:29 PM.
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  #55  
Old 08-26-2012, 01:36 PM
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Simple to check item is to make sure all the heat shields are present underneath each injector ,esp. the one making the noise ,also they can be placed upside down by accident.Stick magnet makes easy work of it.
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  #56  
Old 08-26-2012, 04:04 PM
Oldschoolbenz
 
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Quote:
Originally Posted by chasinthesun View Post
Simple to check item is to make sure all the heat shields are present underneath each injector ,esp. the one making the noise ,also they can be placed upside down by accident.Stick magnet makes easy work of it.
I'm not familiar with this part (heat shield) - where specifically is it located? Is it a mechanical interference (knock) if isntalled backwards.

Thanks.
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  #57  
Old 08-26-2012, 04:10 PM
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It's the seal between the business end of the injector and the prechamber. It's a disk about 15mm across.


Sixto
87 300D
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  #58  
Old 08-26-2012, 04:59 PM
Oldschoolbenz
 
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Quote:
Originally Posted by sixto View Post
It's the seal between the business end of the injector and the prechamber. It's a disk about 15mm across.


Sixto
87 300D

THanks - clear as mud now

So it would not cause a mechanical intereference that i can see - but maybe some combustion anomally.

But if this were the cause - wouldn't it have been eliminated by loosening and also separation of the fuel lines from the injectors?
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  #59  
Old 08-28-2012, 11:56 AM
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To make a sound of a stuck injector is kind of were I was heading with the idea of a heat shield absent in the chamber ,if it wasnt in place Im sure it would play a part in bad injector performance.To say it would make somekind of noise if absent Im not sure of ,maybe somebody else can chime in if theyve had this issue.


Last edited by chasinthesun; 08-29-2012 at 10:47 AM.
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