Author Topic: Ecodiesel engine knock  (Read 16008 times)

Reply #15June 13, 2013, 12:41:46 pm

VTPSD

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Re: Ecodiesel engine knock
« Reply #15 on: June 13, 2013, 12:41:46 pm »
Is it possible that a precup can drop just a little bit and be kissing the piston? I am inclined to think it would have changed in tone or sound level after all those miles at high rpm.
IMO, they can loosen up and rattle, kissing the piston with each combustion event. At some point, they crack apart and spread the love.
im sure hoping that the noise will cease after lifters and rod bearings are new......but that precup is in the back of my mind. Its so consistent, that I doubt that is the issue. I cant imagine it getting hammered millions of times and not getting any worse.
-1991 audi 90 quattro with AHU tdi, r520's holset he211
-1990 audi 90 quattro, holset turbo, 11 second quarter mile demon

Reply #16June 13, 2013, 02:43:28 pm

wolf_walker

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Re: Ecodiesel engine knock
« Reply #16 on: June 13, 2013, 02:43:28 pm »
Might be, I hope not.
I've been driving these things for a long time and never heard of pre-chamber problems till I started reading
online.  My personal opinion which could well be BS is that it's a bad rebuild/abuse/high turbo pressure issue myself. 
I don't doubt it happens and anything can happen with a large enough sample size.  But it isn't something to expect on a good
stock original motor, and I've put as many or more miles on em as anyone.  If the boost is cranked or the head has been monkeyed with, that I can't say about.
It's why I value a virgin VW built motor highly.

You could pull the head.  I know it's grief but it's not that bad a job really once the junk is out of the way.


I have had twice, what I believe to have been pieces of really really hard carbon dislodge in these motors after having had crappy
injectors in em and not being rung out very often, both times hot
at low RPM, and make an ungodly bad tap tap tap tap tap noise.  Sound for all the world like it was about to come apart.
Few minutes later it cleared up and was gone.  One of those motors I had a chance to pull the head off later
and there was a hint of some irregular banging in one cylinder on the piston top and head.  It was slight but it was there.
Both motors lived a long life after.  These things are tuff.
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Reply #17June 13, 2013, 04:25:07 pm

92EcoDiesel Jetta

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Re: Ecodiesel engine knock
« Reply #17 on: June 13, 2013, 04:25:07 pm »
Too late to try this now but next time maybe? In the past, to hunt down noise, I have rigged a contact microphone to a tape recorder and headphones so I can listen and make a recording while driving. By moving the mic around, I can localize the source most of the time. By playing back into an oscilloscope, I can measure the frequency and amplitude of the noise.

Reply #18June 13, 2013, 05:16:13 pm

TylerDurden

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Re: Ecodiesel engine knock
« Reply #18 on: June 13, 2013, 05:16:13 pm »
I put a mech stethoscope on my 89 today, but it isn't making the particular tone, just lifter noise today.  :-\

Reply #19June 13, 2013, 07:02:55 pm

wolf_walker

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Re: Ecodiesel engine knock
« Reply #19 on: June 13, 2013, 07:02:55 pm »
My hearing is so lousy and these SOB's are so noisy, I have a hard time really picking out anything to be honest.
I never new the lifters were as apt to crap out as they are till I had a gasser and then was able to pick up a similar
noise on the diesel, even then I wasn't sure.  But it shut up and ran better with fresh ones.
Always figured when I'm rich (ha-ha) I'll build a mile long retaining wall with a straight road next to it so I can drive along
it with the window open and hear reflected sound.
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Reply #20June 13, 2013, 09:57:37 pm

theman53

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Re: Ecodiesel engine knock
« Reply #20 on: June 13, 2013, 09:57:37 pm »
I don't think the precup would make it 2,000 miles. Mine only lasted about 2 miles of slightly less performance than I was used to and 1/2 mile with a noise before throwing it out.

Reply #21June 13, 2013, 10:46:14 pm

VTPSD

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Re: Ecodiesel engine knock
« Reply #21 on: June 13, 2013, 10:46:14 pm »
I put my new rod bearings in tonight and gave it some fresh rotella. I think the noise is still there, but the motor might be a bit quieter overall. I am pretty sure its a lifter. I found a couple that had a 5 thou gap after being run and bently says replace anything with 4 thou or more gap. I am going to assume its safe to drive until the new lifters arrive. The sound really does seem to be at cam speed, not crank speed.

My hearing is so lousy and these SOB's are so noisy, I have a hard time really picking out anything to be honest.
I never new the lifters were as apt to crap out as they are till I had a gasser and then was able to pick up a similar
noise on the diesel, even then I wasn't sure.  But it shut up and ran better with fresh ones.
you hit the nail on the head with that one. I know there is a new noise, but the engine is so loud to being with its very hard to pinpoint the noise when under the hood, even with the hose to the ear trick or the screwdriver to the ear trick.I can hear it better when standing back from the car, then the louder clatter can be heard over the normal clatter. 
-1991 audi 90 quattro with AHU tdi, r520's holset he211
-1990 audi 90 quattro, holset turbo, 11 second quarter mile demon

Reply #22June 20, 2013, 10:16:39 pm

VTPSD

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Re: Ecodiesel engine knock
« Reply #22 on: June 20, 2013, 10:16:39 pm »
the plot thickens....I put in new INA lifters today. Let them soak for several hours and installed. Started the car and let it idle for several minutes. It was still pretty noisy, but if i revved it a bit the lifter noise would go away, then return at idle. Once warmed up it sounded exactly as it had before   
Still sounds like lifters to me, but not sure. Maybe there is something very broken inside, but i think not since it ran completely quiet for a few breif moments during warm up.
I am wondering if i am not getting adequate oil pressure. The buzzer does work, but I think I will try to get a gauge installed and check the pressure at the head. Is this a common issue with these? Oil pump seemed healthy when I had it out last week. Starting to get frustrated, I would really like to have a motor that didnt have that extra little ticka ticka ticka...
-1991 audi 90 quattro with AHU tdi, r520's holset he211
-1990 audi 90 quattro, holset turbo, 11 second quarter mile demon

Reply #23June 20, 2013, 10:24:48 pm

VTPSD

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Re: Ecodiesel engine knock
« Reply #23 on: June 20, 2013, 10:24:48 pm »
is it possible that i didnt soak them enough? if that is the case should i pull them out and soak them again? grumble.....
-1991 audi 90 quattro with AHU tdi, r520's holset he211
-1990 audi 90 quattro, holset turbo, 11 second quarter mile demon

Reply #24June 20, 2013, 10:29:44 pm

TylerDurden

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Re: Ecodiesel engine knock
« Reply #24 on: June 20, 2013, 10:29:44 pm »
I put in a set a couple weeks ago. I was kinda disappointed that the lifters didn't just run silently - seemed as bad as before I changed them.

But they have been getting much quieter over time.

I also have a gauge, yet to install.  ::)

Reply #25June 20, 2013, 11:07:25 pm

VTPSD

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Re: Ecodiesel engine knock
« Reply #25 on: June 20, 2013, 11:07:25 pm »
Well, I guess that is good to hear. It sounds exactly as it did before. Bummer, but maybe it will improve. Nothing in the valve train showed any signs or abnormal wear or low oil pressure, so i dont think that is the issue.
-1991 audi 90 quattro with AHU tdi, r520's holset he211
-1990 audi 90 quattro, holset turbo, 11 second quarter mile demon

Reply #26June 20, 2013, 11:12:32 pm

wolf_walker

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Re: Re: Ecodiesel engine knock
« Reply #26 on: June 20, 2013, 11:12:32 pm »
Piston slap?

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Reply #27June 20, 2013, 11:21:19 pm

VTPSD

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Re: Re: Ecodiesel engine knock
« Reply #27 on: June 20, 2013, 11:21:19 pm »
Piston slap?

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its possible...but I am hoping no.The noise remains constant when coasting downhill and no power applied, bores looked really nice from the bottom when I was in there, and the noise seems to be at cam speed, not crank speed. But I am not ruling it out. If its piston slap, its just going to get driven until it doesnt drive anymore. The noise started suddenly, and has not worsened at all since, 3000 miles later.
-1991 audi 90 quattro with AHU tdi, r520's holset he211
-1990 audi 90 quattro, holset turbo, 11 second quarter mile demon

Reply #28June 20, 2013, 11:49:27 pm

wolf_walker

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Re: Re: Ecodiesel engine knock
« Reply #28 on: June 20, 2013, 11:49:27 pm »
Vacuum pump? I'm grasping at straws here obviously.

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Reply #29June 20, 2013, 11:51:27 pm

wolf_walker

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Re: Re: Ecodiesel engine knock
« Reply #29 on: June 20, 2013, 11:51:27 pm »
So if you chop throttle at speed in gear, still there or can you tell?

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