Author Topic: Ecodiesel engine knock  (Read 15990 times)

June 11, 2013, 10:36:11 pm

VTPSD

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Ecodiesel engine knock
« on: June 11, 2013, 10:36:11 pm »
Hi All,
I just got back from an epic 3000 mile trip with my 91 ecodiesel. It ran great the whole way, but about 1000 miles into the trip it developed a tapping or knocking that is new. The engine has about 240k on it and i dont think has ever been apart. It runs sweet, and has been very quiet for an idi diesel. This new knock is not horribly loud, can barely hear it with the windows up. Almost sounds like a sticky lifter but it does not seem to be coming from the head.
My instinct says it is coming from the bottom end. It starts after the car has been running about 30 seconds and stays there at all engine speeds. I was forced to drive it another 2000 miles to get back home with it in this state and it never got worse or beter. Still there. Running normally and has all of its power. I almost think it is rod knock, and i might just order some new rod bearing and pull the pan and replace them. I am looking for some other suggestions of things I should check.
I am not sure of when it started for sure, but somewhere out in the flats in indiana i decided (for unknown reasons) to see how fast the old girl could do on the flats. I held it wide open in 5th for maybe 30 seconds or less until it topped out and then coasted back down to 70. I drove basically 70 the entire trip. I am not sure this is when the trouble started but when i stopped for fuel in about 100 miles i noticed the ticking or knocking.
Can i re-use the rod bolts in this engine, or do i need to figure out a way to remove the rod bolts from the rods and replace with the oil pan dropped.
Thanks in advance. I feel bad that I hurt the old girl, and want to get it back into shape again.
« Last Edit: June 11, 2013, 11:03:03 pm by VTPSD »


-1991 audi 90 quattro with AHU tdi, r520's holset he211
-1990 audi 90 quattro, holset turbo, 11 second quarter mile demon

Reply #1June 12, 2013, 11:00:25 am

VTPSD

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Re: Ecodiesel engine knock
« Reply #1 on: June 12, 2013, 11:00:25 am »
i found this video on youtube, mine has a similar sound. Not sure if it helps.
http://www.youtube.com/watch?v=63p-kuHxBEE
-1991 audi 90 quattro with AHU tdi, r520's holset he211
-1990 audi 90 quattro, holset turbo, 11 second quarter mile demon

Reply #2June 12, 2013, 11:02:01 am

VTPSD

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Re: Ecodiesel engine knock
« Reply #2 on: June 12, 2013, 11:02:01 am »
this one is also a similar noise
http://www.youtube.com/watch?v=kFBKHE9rUpc
-1991 audi 90 quattro with AHU tdi, r520's holset he211
-1990 audi 90 quattro, holset turbo, 11 second quarter mile demon

Reply #3June 12, 2013, 11:47:51 am

TylerDurden

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Re: Ecodiesel engine knock
« Reply #3 on: June 12, 2013, 11:47:51 am »
The first vid has a "clinking" timbre that makes me think piston contact with a pre-cup or valve. I have a similar sound in my 89NA that makes me nervous.

The second vid sounds like a lifter .

Reply #4June 12, 2013, 11:54:59 am

VTPSD

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Re: Ecodiesel engine knock
« Reply #4 on: June 12, 2013, 11:54:59 am »
hmmm, i would say mine sounds more like the second than the first. Do lifters ever go bad suddenly and clatter at all RPMs? What is the way to test them. I was thinking maybe get the engine warm, pull the valve cover and try pushing down and see if i have any play in the lifters?
-1991 audi 90 quattro with AHU tdi, r520's holset he211
-1990 audi 90 quattro, holset turbo, 11 second quarter mile demon

Reply #5June 12, 2013, 12:09:55 pm

wolf_walker

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Re: Ecodiesel engine knock
« Reply #5 on: June 12, 2013, 12:09:55 pm »
The hydraulic lifters can and do crap out, and they are pretty cheap.

Did you notice if the noise was there both on and off throttle, as in coasting in gear?

I'm inclined to think it's a non-critical failure if it went 2K miles of interstate driving
and didn't blow or get worse.
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Reply #6June 12, 2013, 12:31:12 pm

bbob203

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Re: Ecodiesel engine knock
« Reply #6 on: June 12, 2013, 12:31:12 pm »
92 Passat wagon M-TDi
03 Jetta wagon TDi
VE Timing tools for rent
Need a car transported a long distance? Pm me for details.

Reply #7June 12, 2013, 12:55:51 pm

VTPSD

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Re: Ecodiesel engine knock
« Reply #7 on: June 12, 2013, 12:55:51 pm »
The hydraulic lifters can and do crap out, and they are pretty cheap.

Did you notice if the noise was there both on and off throttle, as in coasting in gear?

I'm inclined to think it's a non-critical failure if it went 2K miles of interstate driving
and didn't blow or get worse.

As far as i can tell the noise is there no matter what the RPM or throttle input. Does it in neutral the same as in gear and under load. Its not loud enough to hear when going fast, so its hard to do the fuel shutoff test, but I am quite sure it is mechanical and not fuel.
I would think a rod bearing would have gotten worse or spun after all that. 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.
-1991 audi 90 quattro with AHU tdi, r520's holset he211
-1990 audi 90 quattro, holset turbo, 11 second quarter mile demon

Reply #8June 12, 2013, 03:05:18 pm

wolf_walker

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Re: Ecodiesel engine knock
« Reply #8 on: June 12, 2013, 03:05:18 pm »

[/quote]
 I am inclined to think it would have changed in tone or sound level after all those miles at high rpm.
[/quote]

Agree.  Might cut open an oil filter and see if there's sadness inside. 
I'd put lifters in it.
Many things we do naturally become difficult only when we try to make them intellectual subjects. It is possible to know so much about a subject that you become ignorant.
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Reply #9June 12, 2013, 08:57:43 pm

VTPSD

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Re: Ecodiesel engine knock
« Reply #9 on: June 12, 2013, 08:57:43 pm »
Well I spent some time tonight in the shop trying to find my noise. I couldnt really pinpoint the location, so i started by pulling the valve cover with the engine warm to check lifters. Several of them had a very small amount of play, but nothing outrageous. I am not ruling them out, but nothing looked or felt out of wack to me.  ???
Then I pulled the oil pan and wiggled all the rods, everything seemed copacetic, again nothing crazy. There was no evidence of glitter in the oil, but there was some debris in the pan. At first I thought it was metal but upon closer inspection I think it may be stuff that fell in when wiggling the pan off. I checked crank end play, there was some, but seemed to be within the .0147" that the bently says is allowable. The only thing that seemed a bit funny is the main bearing thrust tabs on the middle journal could be wiggled a bit with the tip of a screwdriver. When I slid the crank all the way to one side, you could wiggle the opposite side tab. I actually think this is ok and normal, but i thought it was worth mentioning.

Getting desperate I pulled each rod cap and inspected the bearings since I already ordered the parts in a fit of rage the other night. The pictures below show the bearings. The bearings that are more copper colored came out of the rod side and the non discolored ones came from the cap side.








any thoughts?
-1991 audi 90 quattro with AHU tdi, r520's holset he211
-1990 audi 90 quattro, holset turbo, 11 second quarter mile demon

Reply #10June 12, 2013, 10:29:14 pm

wolf_walker

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Re: Re: Ecodiesel engine knock
« Reply #10 on: June 12, 2013, 10:29:14 pm »
Google "testing hydraulic lifters" it's a leak down rate kinda thing.

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Many things we do naturally become difficult only when we try to make them intellectual subjects. It is possible to know so much about a subject that you become ignorant.
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Reply #11June 13, 2013, 08:02:35 am

theman53

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Re: Ecodiesel engine knock
« Reply #11 on: June 13, 2013, 08:02:35 am »
If those are rod bearings that is how they wear. Mains are opposite. They don't look good to me.

Reply #12June 13, 2013, 08:08:56 am

VTPSD

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Re: Ecodiesel engine knock
« Reply #12 on: June 13, 2013, 08:08:56 am »
If those are rod bearings that is how they wear. Mains are opposite. They don't look good to me.
yes those are rod bearings, so you are thinking they look worn?
 I am replacing them anyhow since its apart and they are cheap.
-1991 audi 90 quattro with AHU tdi, r520's holset he211
-1990 audi 90 quattro, holset turbo, 11 second quarter mile demon

Reply #13June 13, 2013, 10:55:46 am

wolf_walker

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Re: Ecodiesel engine knock
« Reply #13 on: June 13, 2013, 10:55:46 am »
Don't really look bad now that I can see them on a non-phone screen.
I'd plastigauge with the new bearings just to be OCD but I think they are fine
Unless the journals look crappy.
Many things we do naturally become difficult only when we try to make them intellectual subjects. It is possible to know so much about a subject that you become ignorant.
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Reply #14June 13, 2013, 12:19:35 pm

TylerDurden

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Re: Ecodiesel engine knock
« Reply #14 on: June 13, 2013, 12:19:35 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.

 

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