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General Information => Troubleshooting => Topic started by: Quantum TD on January 16, 2008, 07:45:58 pm
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So, I'm at a loss on this one (well not really, I just don't want to open the can of worms and find out).
I've had my friend's 1984 Rabbit 1.6D in my garage for about 8 months now. It came to me with absolutely no compression. I pulled the motor apart in July, and left it apart in the garage while I worked on other paying projects.
Just this past month, I decided to put it all back together. Here's what we did:
Head:
New valves (exhaust only)
New guides (all 8)
New valve seals
Valve job (seats recut)
resurface (decent sander-type resurface)
Correct gasket (1 notch, the old one was a 3 hole).
New bolts
seals, etc.
Bottom end:
New Rings (Std)
New rod bearings
seals, etc
Hone cylinders
Here's where I'm nearly certain the problem lays. When I pulled the pistons, the #2 ring on each piston had cracked in half. I can only assume that someone was shooting ether into the intake for quite some time in order to crack those rings. The other rings were fine, but there was a ton of carbon buildup in the grooves. I didn't mic the bores, as the car is really not worth it. But, the bores looked pretty bad. There was no pitting or scoring, but there was a noticeable ridge at the top. I tried to hone it out, but it would have taken forever. So I just honed each cylinder and cleaned out the bores. Then I reinstalled the pistons with new rings and rod bearings.
I told my friend that we could put it together, and it would run, but there was no telling how long the motor would last or how fuel economy would go, since the compression was bound to be a bit lighter than if we had bored the block and put in new pistons.
So, last night, I got it back together enough to see if it would fire. After some coaxing, and bleeding air from the injectors. It fired up, and sounded quite good for a car that had been sitting for about 10 years. The oil light went out, and I ran the motor for about 10 sec before turning it off: quite pleased with my work.
Since I had started the car with a squirt bottle full of diesel fuel (the tank needed to be cleaned), I spent today cleaning the tank and the lines. I replaced the old crispy lines and bled the system. I also installed a new filter-to-pump line (clear) to see if it was sucking air.
The second I started the car up, it sounded HORRIBLE, as if something was knocking. At first, I thought it was some dirt that got into the injection pump when I replaced the filter-to-pump hose. So, I let it run for a few seconds (again, oil light went out), and loosened each injector line to see if it was air in the line, or if the noise went away when I removed pressure from them. It sounded the same on all 4, and ear-testing the injectors showed that they were not making excessive noise.
So, then I thought about oil pressure. I double-checked the oil, and it was a bit low (about 1 1/2 qts), but not enough to cause any damage, especially since the oil pressure switches showed good. So I topped it off, and went to it again. Same noise and quite loud.
Then, I checked the head. I reasoned that the valves might be hitting or something, despite the fact that I had measured the projection of the pistons, and had properly set the valve clearance (mech head). The lifters all looked good. There was oil in the head and on the cam, and no damage anywhere up top that I could see.
So, i crawled under the car and hand cranked the motor over. The wonderfuld compression I had before starting it, had softened up to mediocre, and there was a palpable feeling in the wrench, from where the noise was clearly coming in the bottom end. Here's the fun part: the noise is continuous, and not episodic. That is, I can feel the noise at all parts in the rotation of the crank. So, it can't be from bent/hit valves, since that would only be noticeable when the pistons came up to (presumably) hit the valves. Also, the car was still running, so it must have decent compression (i.e. not bent valves). So that's good news.
The only thing I can come up with is a bad bearing(s). But what could have caused it? I lubed all the bearings with prep grease. The parts were all clean and grit-free. The car had good oil pressure, and I primed the oil filter before starting, and I primed the intermediate shaft (oil pump). The car sounded great last night, and now it sounds like crap. BUT, if you rev the car up over 2000 RPM, the noise goes away. While it's tempting to think that this fact would rule out bad bearing (or bent rod), all the evidence I have so far really makes me think bad bearings.
I guess it's possible that a ring broke (by hitting the ridge?), but the car idles perfectly (albeilt noisily). This makes me think that the injectors, pump, head and pistons are all ok.
Anyone out there have an experience like this? If so, what kind of damage can I expect on the crank? My dad (who's done this quick and dirty repair method several dozen times), claims that the crank should be fine. Could a piece of dirt in the injection pump cause this type of racket? I'm fairly certain that it's not the pump, but that is the only part on the car that I touched since I started it last night, and the noise appeared instantaneously when I cranked it today after fiddling with the fuel system.
Thoughts anyone??
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You always need to remove any ridge when installing new rings.
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You always need to remove any ridge when installing new rings.
According to the book. Although I have never done it this way before, I have friend's who've done it dozens of times (simple hone and re-ring), and my father's done it to at least 2 dozen diesels back in the day. They never had problems. In fact, my VW mechanic friend who does side work, re-ringed a 1985 Golf about 7 years ago that had about 175k on it, and he still sees it on the road.
Also, I may have overemphasized the ridge. I would have liked to rebore, because I too like to go by the book, but it wasn't a 'fingernail -catching' type of ridge, just a wave near the top that seemed more pronounced after I honed with a straight hone. With the dingle-berry hone, it looked fine and you wouldn't even know it was there.
Anyway, I guess I'll find out tomorrow when I drop the pan, and/or drop a few sticks of TNT in the car.
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If you disconnect the rods and push the pistons up out of the way do you still get the resistance. If it is rod or ring related it should go away. If not I'm thinking thrust bearing worn or damaged to push the crank forward or back in the block, or even insufficient thrust clearance. Sounds like you will have to pull the motor and crank to determine the cause. I have found that taking everything apart is usually faster than trying to troubleshoot with everything still together. Not really enough information to do more than wild guess. Keep us posted, Dan
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Just inspected the rod bearings. They all look good. No wear on those.
Then I pulled the lower mains (#s 2,3,&4): all had wear (not excessive) on the lower bearings. Basically, the aluminum caoting had worn down on the centers. ON the # 3, it's close to the copper. I haven't checked 1 & 5 yet, or the top beaings. But, there are some copper flakes in the pan (new, as I had cleaned the pan before reassembly).
Could this cause my problem?
What I'm thinking is this:
1) Before the rebuild, the car had no compression
2) The car sat for 5-10 years before rebuild. While I lubed all the parts that I installed (wrist pins, rings, rod bearings), I didn't lube/inspect parts that I did not replace (i.e. main bearings, intermediate shaft bearings)
3) Since I lubed all those parts, they're probably not the problem. Also, if the intermediate shaft bearings were bad, I'm sure that I'd get the oil buzzer on the dash, as I'd be losing oil pressure. No?
4) Since the car had no compression, perhaps had no lube on the mains after sitting for 5-10 years, then perhaps the new compression on dry mains may have caused the wear.
I'll post an update once I check the rest of the mains. In the meantime, if anyone has some idea.... My dad actually thought wrist pins.
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Yeah, dry bearings isn't a good thing. Probably better check the intermediate shaft as well as if the mains got hosed, they probably did too.
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Did you happen to do a ring end gap check in the bores before installing them on the pistons?
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Did you happen to do a ring end gap check in the bores before installing them on the pistons?
Nah. This was to be done on the cheap.
Here are some current thoughts on the matter:
1) Ring #2 on all pistons was cracked.
2) There was HEAVY carbon buildup behind the rings. It took me about 4 hours to scrape all the crap out.
Could the knocking be piston slap? It usually goes away when the motor gets warm. But I haven't gotten it warm yet, since the noise is so horrendous, I'm afraid to run it long. The cylinders were worn, and then I honed them, so there may be too much clearance now.
The only other option is bad main bearings. But would they make noise at low RPMs and disappear at higher RPMs? Seems like bad main bearings would make noise at higher RPMs and under load.
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Yeah, dry bearings isn't a good thing. Probably better check the intermediate shaft as well as if the mains got hosed, they probably did too.
I just checked the IS bearings. They look fine, and there's no play in the shaft.
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maybe the rings need to seat? if all looks good maybe thats how the car will run... any injector work done? maybe they're just stuck from sitting so long. try running that diesel purge?
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"Could the knocking be piston slap? It usually goes away when the motor gets warm."
More than likely this is your culprit. It will probably run for a good long time. Just be cautious to keep the rpm up and not lug the motor. Could also be in addition to the slap, a leaky or poor pattern injector(s) that is aggravating the slap condition.
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maybe the rings need to seat? if all looks good maybe thats how the car will run... any injector work done? maybe they're just stuck from sitting so long. try running that diesel purge?
Good points. I think I've narrowed it to the following possibilities or any conbination therof:
1) Bad wrist pins (unlikely)
2) Rings seating (likely)
3) Piston rock or slap (possibly)
4) Injection pump (maybe: I might have dropped a bit of dirt in there when playing with the fuel lines). Could air in the lines sound that bad (like hammering). I loosened all the union nuts on each injector, and the sound remained.
The noise definitely is not coming from the crankshaft, despite the slight wear on those bearings.
I can feel the pistons move in the cylinder as the rings scraping against the cylinder walls. Do seating rings make that much noise? It occurred to me that this is possible, since there is really nothing lubricating the pistons as they move. The rods are not rifle-drilled, so the only lubrication for the pistons has to be oil that is slung around inside the crankcase.
Another thing that occurred to me is that it may be a broken clutch disc or pressure plate or something? The noise really sounds like what you might hear on a Jeep or a Chevy with a cracked flywheel, but I've never seen it happen on a VW before.
As for the piston slap, from the few things I've googled that has sound bites, piston slap should make the car just sound MORE like a diesel, rather than sound like something hammering.
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what is the timing set to? more advanced? mines at 1.06 approx and with the cold start pulled all the way out it has a really pronounced 'slap' :lol: maybe the injectors are worn though...
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what is the timing set to? more advanced? mines at 1.06 approx and with the cold start pulled all the way out it has a really pronounced 'slap' :lol: maybe the injectors are worn though...
Timing is set at .98. I did pull the cold start lever out. That's something to look at.
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After much research and deliberation, I think that it can only be one of two (maybe 3) things).
1) Piston slap. This would explain why the noise is present when cold. One test would be to see if the noise goes away when the motor warms up.
2) Broken clutch, pressure plate, or flywheel. While I've never seen this happen on a VW, the symptoms mimic that of a broken flexplate (although this car doesn't have one). When you rev the car up, the noise goes away.
3) Injection pump. Not sure why the car would make a knocking sound via the IP, but I guess anything's possible. Air or dirt in the pump? Don't know.
So, I guess I'm going to put it all back together and run it in the yard for a while to see if the noise goes away. If the noise goes away (or lessens) once the car heats up, I'll know that it's piston slap. If it doesn't go away except when the car revs up, then I'll look to the clutch, pressure plate, flywheel area. If the noise gets worse at all RPMs and temps, then I'll just start over and mic the pistons and the bores.
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Hopefully no rods come through the block or anything like that :shock:
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Maybe you get to take the quiz twice. Once for the before problem, once for the result of running it with the problem. :lol: :lol: :lol:
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my car makes this 'slapping' noise at low rpms that cuts out once i reach 2k rpm. its like a rattle... it must be from the timing advance because when the engine is hot and cold start is pulled it isn't as pronounced. just an idea. hopefully you don't have 'stuck' injectors...
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Hopefully no rods come through the block or anything like that :shock:
I doubt it. Like I said, if it were a rod bearing or a bent rod, the noise would get worse with RPMs, and it doesn't. Also, when I pulled all the bearing caps, the jounrals and bearings all looked fine, with the original main bearings showing some mild wear.
It may be in the pump. Like I said, the only difference between when I first started it (and it sounded good), and the second time when it sounded like poo, was that I pushed in the clutch, I pulled the cold-start lever, and I replaced the fuel line and began sucking fuel from the tank.
It all may be coincidental, or not.
I'll post an update.
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Hopefully no rods come through the block or anything like that :shock:
I doubt it. Like I said, if it were a rod bearing or a bent rod, the noise would get worse with RPMs, and it doesn't. Also, when I pulled all the bearing caps, the jounrals and bearings all looked fine, with the original main bearings showing some mild wear.
It may be in the pump. Like I said, the only difference between when I first started it (and it sounded good), and the second time when it sounded like poo, was that I pushed in the clutch, I pulled the cold-start lever, and I replaced the fuel line and began sucking fuel from the tank.
It all may be coincidental, or not.
I'll post an update.
if the noise didn't go away with cracking all 4 injector lines it could be the pump... for a cheap refresh of the motor your best option may be to use some lubro moly diesel purge. might actually work if the car was sitting and has stuck vanes.
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How long did you run it initially? Did you run it for 15 or 20 minutes or at least until it was up to normal operating temp? I've heard some errant noises on rebuilds that go away once it's worn in a little.
Andrew
Yeah. That's what I'm gonna do. I only ran it for at most 3 or 4 1-minute stints because the noise was so beastly. I'm gonna slap on a different pump, reassemble it, hook up a oil pressure gauge, and run it hard. If if blows up, no biggie. The owner (my friend) is aware of the situation, I've got spare blocks, and I've got no expectations out of this motor.
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Take video. :P :lol: :lol:
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Sting clankin away. Any chance it's the wrist pins?
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Sting clankin away. Any chance it's the wrist pins?
Not likely.
How did they feel when you had them out?
Wrist pins just don't go bad (that I've seen) under normal operation.
The engine I just rebuilt http://www.dubnetworks.net/showthread.php?t=1748 had over 200k on it and the wrist pins were perfect...
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After much research and deliberation, I think that it can only be one of two (maybe 3) things).
1) Piston slap. This would explain why the noise is present when cold. One test would be to see if the noise goes away when the motor warms up.
2) Broken clutch, pressure plate, or flywheel. While I've never seen this happen on a VW, the symptoms mimic that of a broken flexplate (although this car doesn't have one). When you rev the car up, the noise goes away.
3) Injection pump. Not sure why the car would make a knocking sound via the IP, but I guess anything's possible. Air or dirt in the pump? Don't know.
So, I guess I'm going to put it all back together and run it in the yard for a while to see if the noise goes away. If the noise goes away (or lessens) once the car heats up, I'll know that it's piston slap. If it doesn't go away except when the car revs up, then I'll look to the clutch, pressure plate, flywheel area. If the noise gets worse at all RPMs and temps, then I'll just start over and mic the pistons and the bores.
I finally got around to looking at this heap of *** again. It's been sitting in the yard since January. Today, my pops and I took a look at it. He was convinced the pistons were hitting the head. I thought it could be a possibility, given that the original HG was a 3-hole (presumed replacement), and I used a 1-notch, based on the piston projection and what the book called for.
Well, we pulled it apart: no contact on the head, valves or pistons. So, we look the bottom end. We ended up pulling the pan (for the second time) to inspect the bearings and wrist pins. We finally figured out what the problem was. It was Door Number 2.
Basically, someone had recently replaced the clutch, pressure plate and flywheel. Since the car was bought from a j-yard, we had absolutely no information on vehicle history. As it turns out, they replaced the clutch and pressure plate, but did not torque the bolts down enough, nor did they use any locktite to seal them on. The bolts loosened up, and the whole pressure-plate/clutch/flywheel assembly would rock back and forth on each compression stroke. At higher RPMs, the whole assy would pin itself against the loose bolts, and the noise would go away.
FUN STUFF. Who in thier life has ever seen that ***? I ended up pulling the pan twice, and today I pulled the head off, just to confirm what I had suspected at first. This should be a lesson. Trust your instincts.
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yea... because now you need 10 new head bolts, a head gasket, AND pull the tranny to get at the clutch :(
glad to hear it was something minor though!
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I literally know nothing but something tells me that fuel delivery can't make that amount of racket that you're describing... i've had tons of air coming from the filter to the pump and it just made it run terribly, no excessive noise. Same with knocking injectors. Sounds odd like valves being eaten but not nessisarily hammering. Perhaps all four injectors are knocking so one can't sound different than another? but im sure you've figured it out it's bottom end.
I'm young and stupid, I'd drive it around the block a couple times (im assuming it has no insurance).
Drivability would tell you a fair amount of information IMO.
Especially if you could find another IDI vw to compare.(that goes with injector knock too)
This thread is really really insightful!
thanks for taking the time to post in such detail!!!!!
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Not the same motor but a few years ago i installed a locally rebuilt 1.7 aircooled gasser into a bus. Drove for a day or 2 before giving it back to the customer. On my first hard throttle , heard some knocking, then bam -rod through the block. Got another rebuilt, drove it again, then had a similar noise on overrun,so shut it down ,towed it across town [$200 !] not to take a chance. Removed the motor, check this and that. Finally realized the drive plate rivets for the auto stick were working them selves loose.
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"Basically, someone had recently replaced the clutch, pressure plate and flywheel. Since the car was bought from a j-yard, we had absolutely no information on vehicle history. As it turns out, they replaced the clutch and pressure plate, but did not torque the bolts down enough, nor did they use any locktite to seal them on. The bolts loosened up, and the whole pressure-plate/clutch/flywheel assembly would rock back and forth on each compression stroke. At higher RPMs, the whole assy would pin itself against the loose bolts, and the noise would go away. "
Not the same motor but a few years ago i installed a locally rebuilt 1.7 aircooled gasser into a bus. Drove for a day or 2 before giving it back to the customer. On my first hard throttle , heard some knocking, then bam -rod through the block. Got another rebuilt, drove it again, then had a similar noise on overrun,so shut it down ,towed it across town [$200 !] not to take a chance. Removed the motor, check this and that. Finally realized the drive plate rivets for the auto stick were working them selves loose.
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After much research and deliberation, I think that it can only be one of two (maybe 3) things).
1) Piston slap. This would explain why the noise is present when cold. One test would be to see if the noise goes away when the motor warms up.
2) Broken clutch, pressure plate, or flywheel. While I've never seen this happen on a VW, the symptoms mimic that of a broken flexplate (although this car doesn't have one). When you rev the car up, the noise goes away.
3) Injection pump. Not sure why the car would make a knocking sound via the IP, but I guess anything's possible. Air or dirt in the pump? Don't know.
So, I guess I'm going to put it all back together and run it in the yard for a while to see if the noise goes away. If the noise goes away (or lessens) once the car heats up, I'll know that it's piston slap. If it doesn't go away except when the car revs up, then I'll look to the clutch, pressure plate, flywheel area. If the noise gets worse at all RPMs and temps, then I'll just start over and mic the pistons and the bores.
I finally got around to looking at this heap of *** again. It's been sitting in the yard since January. Today, my pops and I took a look at it. He was convinced the pistons were hitting the head. I thought it could be a possibility, given that the original HG was a 3-hole (presumed replacement), and I used a 1-notch, based on the piston projection and what the book called for.
Well, we pulled it apart: no contact on the head, valves or pistons. So, we look the bottom end. We ended up pulling the pan (for the second time) to inspect the bearings and wrist pins. We finally figured out what the problem was. It was Door Number 2.
Basically, someone had recently replaced the clutch, pressure plate and flywheel. Since the car was bought from a j-yard, we had absolutely no information on vehicle history. As it turns out, they replaced the clutch and pressure plate, but did not torque the bolts down enough, nor did they use any locktite to seal them on. The bolts loosened up, and the whole pressure-plate/clutch/flywheel assembly would rock back and forth on each compression stroke. At higher RPMs, the whole assy would pin itself against the loose bolts, and the noise would go away.
FUN STUFF. Who in thier life has ever seen that ***? I ended up pulling the pan twice, and today I pulled the head off, just to confirm what I had suspected at first. This should be a lesson. Trust your instincts.
I saw this once and it was my fault!!!....I did a new engine in my sis's cherokee and forgot to torque the flywheel bolts I thought the crank had broken!!!...pulled the tranny and the clutch....lo and behold I left the damn flywheel bolts loose ....DOH!!!...tightened everything back up and good as new!!!!
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I replaced a motor with an old one I had kicking around. When I started it up it ran perfect. Then I went around the block, and it started knocking exceptionally loudly, as if I had spun a bearing. Oil pressure was perfect, and the needle wasn't bouncing around as if a bearing was done. I changed the injectors over to the ones from the motor that came out, and noise was gone. Bad injector!!!