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Hello all, I'm new to the forums & this is my first post. I'm a 45+ year old auto tech, with more than 20 years in the business. I specialize in Honda & Acura auto's, but have dabbled in almost everything over the years. My diesel experience is limited to military applications, mostly 25 years ago. Turbo experience is next to zero. Needless to say, I need some advice.

The patient is my Mothers 2000 Beetle TDI. 1.9L - 5 speed - 189,000 miles. They have owned it since new & have never had a single major problem. Minor problems over the years, glow plugs, broken glove box, window switches & one time the drivers seat wouldn't stay in position. I have been able to take care of everything myself (I did ask a friend for help with the timing belt @ 100K). Other than general maintenance, it has been a very good car, until.......

Last week. My mother called me saying that the car suddenly lost power, started running rough, stalled & was blowing black smoke out of the tail pipe. I advised her to not drive it & sent our wrecker out after it. When it arrived at my shop, I went out to take a look at it. It only took me a minute to determine, with my 45+ years of life experiences, that it was broke.

So, over the last few days. I poked, prodded, played, prayed & even cussed a little at this fine little farfegnugen. I came to the realization, that...... it was broke.

But seriously, it's bad. No compression in Cylinder #1. The piston in cylinder #1 is coming apart. In places it looks like it has started to melt. It has melted the cylinder wall an alarming amount. The head, for that cylinder, looks to have deposits melted into it (see pictures below). Obviously the cylinder will need to be re-sleeved & the piston replaced. Maybe, I should look for a used engine. My question is, what the heck happened & why?

This was a sudden, catastrophic failure. No warning, at all. The car was only driven 2 miles that day, when the incident occurred. She said that it was running fine, like every day she has driven it for the last 11 years. Then, suddenly, it wasn't. It looks to me like this has been going on for awhile. Maybe it just got so bad that a ring finely broke & thats why it lost compression. I don't know.

I know that I can fix this. Have the engine sleeved, a few new pistons, or just a used motor. My question is why. I don't want to fix the engine just to have this happen again. Was it lack of fuel, too much air, or something else? I need to know why & most importantly, how do I keep it from happening again?

I've rambled on long enough. I will let the pictures speak for themselves. I am eager to learn from those of you that are much smarter than I on this matter. Thanks - In Advance - Darren from Maryland.











 

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That's mad, it certainly looks broken, I wonder if it'd be worth getting the injectors looked at, maybe #1 has been throwing in far to much fuel, I'm only guessing though.:)

welcometomyturbodies
 

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That's mad, it certainly looks broken, I wonder if it'd be worth getting the injectors looked at, maybe #1 has been throwing in far to much fuel, I'm only guessing though.:)

welcometomyturbodies
I was thinking about the injectors, or maybe the pump. But, I was thinking the opposite, not enough fuel. Lean burn condition would make it run hot. But wouldn't there of been some kind of warning? It did set a misfire cylinder #1 one code, after the fact. I read the code & said, out loud, DOH.

Anyway, thats a start. I guess, I'm hoping that this has happened to some of you out there & that I can get some advice on keeping it from happening again. But, it would be my luck, that I'm the only one that this has ever happened to before. Again... DOH
 

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Lol you're the first one I've seen so far anyway, I don't know about your mother but mine could wreck a car in no time, she makes a manual sound like an auto and when she tries to top up any of the engine fluids it usually results in me having to fix something, the last time she put antifreeze in the washers and screenwash in the brakes:eek Thakfully my mother doesn't drive anymore so I have more free time:D
 

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A gas engine will run hot if run lean, your diesel engine will run hot if it's too rich. A diesel is always running pretty lean under most conditions compared to full "throttle".

If an injector had failed and was streaming fuel you'd find some melting like that. I've never seen something like that though :) Thanks for the pics! Do you have a pic of the whole fuel nozzle? What are the markings on it? It looks funny to me, here is what my nozzles looked like:
 

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diesels are different
i'm only 19 years old; your experience doubles my age easy, so you may disregard what I have to say, if you want
but i've read a lot, and i've been around diesels all of my life.

they do not require a stoichiometric fuel ratio. in other words, they can have different amounts of fuel to air parts, and be just fine (except in extreme events...).

in fact, diesels need to run WAY lean compared to gassers. they need all of that air in the combustion chamber to compress to about 500 psi to get hot enough to burn the little amount of fuel injected. this is what creates the Nox emissions because when the hydrocarbons are done burning, there is still oxygen left in the combustion chamber. diesels don't constantly try to keep an air/fuel ratio like their gasoline counterparts. To get power, diesels could increase fuel, or increase air by way of boost pressure....either one... OR BOTH!!! :thumbsup whereas gasoline engines just try to cram more of their precious stoichiometric fuel ratio into the combustion chamber.

also, they work just opposite of a gasoline, the more air you pump into them, the cooler they run. the more fuel you run through them, the hotter they run. this is what makes them so much better recipients to turbochargers because it introduces more air to keep the engine cool as it also introduces more fuel. I can prove it by suggesting that you think about an NA diesel (old school [no offense] lol) now when you step on the accelerator pulling a heavy load, there's going to be a LOT of black smoke pouring out the tail pipe and the egt's are going to soar, right? an NA diesel sucks the same amount of air in the combustion chamber every time no matter how much fuel you dump in. so the more fuel, the hotter it gets.

i'm in favor of the injector going bad. at that milage, the springs were probably worn so it was probably popping too long, increasing compression, and/or cilynder temperatures which melted that poor aluminum piston. R.I.P.

its nice to have the injectors pop tested and set every once in a while to make sure they're all popping at the right time, pressure and duration.

I too have never seen or heard about it happening on a tdi, but surely its happened to someone... i've seen it happen big time on our older farm tractors. :D

but it sounds like a fun project to work on
 

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Discussion Starter #8
A gas engine will run hot if run lean, your diesel engine will run hot if it's too rich. A diesel is always running pretty lean under most conditions compared to full "throttle".

If an injector had failed and was streaming fuel you'd find some melting like that. I've never seen something like that though :) Thanks for the pics! Do you have a pic of the whole fuel nozzle? What are the markings on it? It looks funny to me, here is what my nozzles looked like:
Thanks for the info. I had no idea that a diesel would run hotter with more fuel. That seems backwards to me. Thats why I'm here, to learn & grow. It figures, that I would have something that no one has seen before. Having the injectors checked sounds like good advice.

The last picture is of my melted glow plug, not the injector. I assume that is what you are asking about. If not, I would be happy to remove it & take a picture.

Keep the advice coming, I need it.

Thanks - Darren
 

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diesels are different
i'm only 19 years old; your experience doubles my age easy, so you may disregard what I have to say, if you want
but i've read a lot, and i've been around diesels all of my life.

they do not require a stoichiometric fuel ratio. in other words, they can have different amounts of fuel to air parts, and be just fine (except in extreme events...).

in fact, diesels need to run WAY lean compared to gassers. they need all of that air in the combustion chamber to compress to about 500 psi to get hot enough to burn the little amount of fuel injected. this is what creates the Nox emissions because when the hydrocarbons are done burning, there is still oxygen left in the combustion chamber. diesels don't constantly try to keep an air/fuel ratio like their gasoline counterparts. To get power, diesels could increase fuel, or increase air by way of boost pressure....either one... OR BOTH!!! :thumbsup whereas gasoline engines just try to cram more of their precious stoichiometric fuel ratio into the combustion chamber.

also, they work just opposite of a gasoline, the more air you pump into them, the cooler they run. the more fuel you run through them, the hotter they run. this is what makes them so much better recipients to turbochargers because it introduces more air to keep the engine cool as it also introduces more fuel. I can prove it by suggesting that you think about an NA diesel (old school [no offense] lol) now when you step on the accelerator pulling a heavy load, there's going to be a LOT of black smoke pouring out the tail pipe and the egt's are going to soar, right? an NA diesel sucks the same amount of air in the combustion chamber every time no matter how much fuel you dump in. so the more fuel, the hotter it gets.

i'm in favor of the injector going bad. at that milage, the springs were probably worn so it was probably popping too long, increasing compression, and/or cilynder temperatures which melted that poor aluminum piston. R.I.P.

its nice to have the injectors pop tested and set every once in a while to make sure they're all popping at the right time, pressure and duration.

I too have never seen or heard about it happening on a tdi, but surely its happened to someone... i've seen it happen big time on our older farm tractors. :D

but it sounds like a fun project to work on
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Age & experience are two entirely different things. I may be more than twice your age, but it is obvious that your much more knowledgeable on this subject than I am. I appreciate your input & you are reinforcing what others are saying. Too much fuel is bad.

I just wish someone else has seen this. I guess if I have the injectors checked & #1 is bad, I will have found my smoking gun. Without the smoking gun I am hesitant to proceed. I just don't want to rebuild this & not fix the actual cause.

It has only been a few days & my Mother is already nagging me about when is she going to get the car back. I just want to get this repaired & move on. We are very busy & I really don't have time to play with this. Sometimes, having family close is a pain.

I do have a problem with one thing you said. What part of this sounds like fun? A major project on a vehicle that I know nothing about, have no tools, reference materials or time to devote to it. Also, I will not be getting paid, it will probably end up costing me money & anything that ever goes wrong with it will somehow be my fault. None of this sounds like fun to me. But hey, thats just me.

Everything else that you said sounds like excellent advice. Your input is greatly appreciated.

There is one thing that I think we can all agree on. It's broke.

Thanks Again - Darren
 

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Stroud I know you like tdi's but I think you might want to go out sometime and do other things too:D
NOOO!!!
I spent all day today working on my tdi, and if i smoked, i'd be able to compare it accurately to an addiction! I just can't explain it lol

going out and doing other things is cool i guess... but the tdi and diesel theory is where its at!!!

:nana2:
 

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"its broke"
i love it!

but yeah,
if it were me, i'd do the rebuild
you might learn somethin'! and i think that's one thing worth more than what time and money can buy.

also, think about it this way, your mother loves it that her son can save her thousands of dollars in repairs on her car because she has a son that has the means, and the resources to get the job done at only parts cost. If she took the car to a dealer, its no telling what she'd walk out of there paying...
 

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Welcome to the forum Darren. welcometomyturbodies

stroud2010 is correct in describing the differences between petrol and diesel combustion they are different.

From the picture that No.1 cylinder has over heated. Is that the only cylinder thats showing signs of melted aluminium?

The picture of the head No.4 cylinder looks darker then the other 3 so it looks like 3 cylinders have been getting hotter than they should do. I would remove the water pump and check the impellor is still attached. You say she only drove 2 miles before it happened so it wouldn't have got up to normal temperature so this problem could have been happening for a while.

Does your mother notice gauges or warning lights?

Could it be the injector causing this problem? This is a funny one to me, the injector sprays a measured amount of atomised fuel into the cylinder which self combusts due to the internal temperture. If an injector was faulty you would notice that the engine isn't running smoothly plus you may get black smoke out of the tail pipe as she said. Your mum said the engine was running fine but would she know? You could have the injectors checked to see if they are serviceable. You could have them serviced then you will have a good set in case they are needed for the replacement engine.

You can google it this problem.

Melted Piston and Cylinder wall, Too Much Boost? thats something else that needs to be checked.

PD Melted piston

What to do? As you say you are busy with other work in your shop. So you don't have time to rebuild the engine so if you get another motor without knowing its history its pot luck on it condition unless you hear it before its removed. ;)
 

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Thanks for the info. I had no idea that a diesel would run hotter with more fuel. That seems backwards to me. Thats why I'm here, to learn & grow. It figures, that I would have something that no one has seen before. Having the injectors checked sounds like good advice.

The last picture is of my melted glow plug, not the injector. I assume that is what you are asking about. If not, I would be happy to remove it & take a picture.

Keep the advice coming, I need it.

Thanks - Darren
Whoops, sorry I had a brain fart looking at the tip and seeing France. Yes, that is indeed a glow plug! My brain pistons had melted!
 

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If you have a gas turbo engine and are tuned on the edge, running rich will help prevent detonation and cool the EGT. It's a common tuning trick to get a little more power. Of course, they still have to stay within a relatively narrow band around 14:1 to run well.
 

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Welcome to the forum Darren. welcometomyturbodies

stroud2010 is correct in describing the differences between petrol and diesel combustion they are different.

From the picture that No.1 cylinder has over heated. Is that the only cylinder thats showing signs of melted aluminium?

The picture of the head No.4 cylinder looks darker then the other 3 so it looks like 3 cylinders have been getting hotter than they should do. I would remove the water pump and check the impellor is still attached. You say she only drove 2 miles before it happened so it wouldn't have got up to normal temperature so this problem could have been happening for a while.

Does your mother notice gauges or warning lights?

Could it be the injector causing this problem? This is a funny one to me, the injector sprays a measured amount of atomised fuel into the cylinder which self combusts due to the internal temperture. If an injector was faulty you would notice that the engine isn't running smoothly plus you may get black smoke out of the tail pipe as she said. Your mum said the engine was running fine but would she know? You could have the injectors checked to see if they are serviceable. You could have them serviced then you will have a good set in case they are needed for the replacement engine.

You can google it this problem.

Melted Piston and Cylinder wall, Too Much Boost? thats something else that needs to be checked.

PD Melted piston

What to do? As you say you are busy with other work in your shop. So you don't have time to rebuild the engine so if you get another motor without knowing its history its pot luck on it condition unless you hear it before its removed. ;)
Hello,

Excellent points all around. I hadn't paid much attention to the other cylinders. I guess the melted piston captured all my attention. No reported over heating or check engine lights. All the other pistons look OK. But, as you have pointed out, cylinders 2 & 3 also look to be running lean, or maybe very hot.

I will look into the water pump after I pull the motor. That looks to be a very plausible scenario. I replaced the pump when we did the timing belt @ 100K. But that really doesn't matter now. It was a factory pump from the VW dealer. I appreciate the different perspective & another possible smoking gun. I like this idea, It is something that I will be able to physically see when I remove it.

I will also have all the injectors checked, to make sure that they are OK. I need to be sure that everything I put back on this motor is new, or known good.

My mother said that the car was running normally, with no indication of any problems. I believe that she would of known if something major was wrong. She did, after all, notice that something was amiss after the piston had melted. I say again... DOH.

On another note, these things are shocking expensive to repair. My local machine shop quoted me a minimum of $1600.00 to re-sleeve the engine, replace pistons, rings & bearings. I almost choked when I heard that. I also do not know if the head has suffered any damage. A few calls to some local scrap yards yielded similar uncontrollable gaging reflexes. My first call, to someone I deal with all the time, netted me a 01 Jetta engine with 76K on the odometer for $2500, complete. I thought he was joking, but a few calls later, I realized he was giving me a good deal. I don't know what way to go here. Without the smoking gun I would rather replace everything. But then, you never know what you will get when you go with a used part. The adventure continues.

I have to admit, I am a little intimidated by this. My lack of experience, reference materials, & tools with diesels, turbos & European cars in general, has me wanting to play this one very safe. Also, time is a huge factor here. With the change in the weather, we are getting very busy. If this was anyone else's car I would of blown it down the road almost immediately. No offence, but this is just a little far outside of my comfort zone. But, as with everything else, if I throw enough time & money at it, It will leave here, under it's own power. At least, at the moment, that is my plan.

Thanks for the input - Darren
 
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