VWDiesel.net The IDI, TDI, and mTDI source.
Engine Specific Info and Questions => IDI Engine => Topic started by: Vincent Waldon on February 07, 2010, 08:54:21 pm
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I posted these pictures over in the TDI section but the story could be an IDI one. For those of you not familiar with TDI pistons the hole in the middle is supposed to be there, but not with the radiused edges:
http://www.vwdiesel.net/forum/index.php?topic=24493.0 (http://www.vwdiesel.net/forum/index.php?topic=24493.0)
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wow thats crazy. haha makes me wanna replace my fuel injectors right now
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TDIs spray the fuel directly into the piston so you could argue that they are more susceptible to this kind of damage... but a mis-firing injector can make a mess in an IDI as well... good idea to have 'em pop-tested every now and then. ;)
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the pistons in the motor I just rebuilt have been hurt by poor injector spray(from heat shields installed upside down) ran for less that 100 miles before being pulled apart(according to the PO) to see why it was running so poorly.
(http://i229.photobucket.com/albums/ee139/truckinwagen/PA230004.jpg)
I can only imagine what it would be like with 10,000 miles.
-Owen
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That's a great picture... thanks for posting.
Classic IDI injector erosion... starts at that one particular spot on the piston thanks to the orientation of the pre-chamber. As you say... if it's that noticeable after 100 miles... :o
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and thats with new injectors and fresh rebuilt motor, the only thing I could find wrong was heat shields installed upside down.
apparently they sealed well enough to run, but it inhibited the spray pattern enough to run like garbage, smoke like a train and erode the pistons.
the PO couldn't figure out what was wrong, gave up and sold me the motor for $100.
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by the way, what bent the rod on that motor and how long was it run with a bent rod?
might running with a bent rod do the same as a bad injector without having a bad injector?
the loss of compression keeps the fuel from burning properly, which lets the fuel pool(much like a poorly firing injector)
just a thought...
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Yup, that's a reasonable theory. Here's the story on this particular car:
I bought the car for a very very very reasonable price... parked it as soon as I got it as the timing belt was about 150K overdue. :o
Did the timing belt, took it out for a test drive... 2km later bang went the turbo seals and the engine hydralocked on the resulting slug of oil.... limped about 1km home. So it had about 1km on that bent rod. :P
All 4 rods were bent... that one the worst. Compression was 450/300/100/300.
Ah well... new overbore pistons and beefy aftermarket rods are on the way...couple of weeks from now I'll have a brand-spanking-new engine in my latest "project" car... thank heavens for an understanding family. ;D
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ah, if you know when the "event" that bent the rod happened then its even money on a bad injector.
just wondered if it had run very long with a bent rod.
a buddy of mine had what he thought was a wrist pin for about 10,000 miles on his straight six jeep.
pulled it apart to find a bent rod, ran fine and made good power for that whole time, never would have thought that it was a rod until we pulled it apart.
-Owen
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So that's what a melted piston looks like :o good to learn about that now before I finished my build. I just cleaned the pistons in the 1.6 TD bottom end that I have, and have this issue on more than one piston, guess it's time to get new pistons, thought it was from oxidation at first, can't run an engine like that in my setup. Good writeup, very informative. I'll post up pics tomorrow. The good news is I recovered everything from the totaled car, but the bad news is that I have some damaged parts now :'( will need a new set of 1.6 td rods and pistons, mine say .030 on em, oversize? I promise pics soon
Kevin
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injector erosion on the top of the piston is fine. it will run fine too. my pistons are eroded farther away than that with no problems. those pics were 100 miles of driving, not normal erosion that takes years and thousands of miles.
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I would still rather run new pistons in my setup, don't want ANY! unexpected hiccups in the build, and hopefully won't have to tear it down at all. Besides, the pistons were damaged in the crash and dented and got beat up a little :'( I'm ok though, and so was the other guy 8)
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Nice pics, I'm on the original injectors still, when I get home I'll pull em and get them pop tested.
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the pistons in the motor I just rebuilt have been hurt by poor injector spray(from heat shields installed upside down) ran for less that 100 miles before being pulled apart(according to the PO) to see why it was running so poorly.
(http://i229.photobucket.com/albums/ee139/truckinwagen/PA230004.jpg)
I can only imagine what it would be like with 10,000 miles.
-Owen
The PO clearly did not replace the pistons before installing the heat-shields upside down on his "Rebuild". You can clearly see the impact marks from valve contact: probably the reason for the "rebuild" in the first place. Minimally, those are used pistons with more than 100 miles on them. As Rabbit on Roids notes, it's fine so long as it does not affect the piston ring lands.
In other words, that's about 100K+ worth of piston erosion rather than 100 miles worth. About what you'd expect to see from a car with over 70k on it at the least. While I agree it's good to rebuild/test/replace your nozzles every 50-100k, I don't think the average person really needs to worry about injectors that much if your car is running fine.
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well being OS(second or third, I cant remember) pistons, they were replaced at some point in this motors life.
I'll bet that the valve impacts are another symptom of a PO that had no idea what he was doing, the bores still had crosshatching, and the piston skirts were so clean and free of wear that I am prepared to believe that they had very little time on them.
it is true that stories from the PO are often sketchy at best, but from what I could see from the wear on all the motor parts, I am prepared to believe that the erosion was greatly accelerated by having the heat shields installed upside down.
-Owen