Bad bearings or bend rod? Quick quiz

[burn_your_money]

Hopefully no rods come through the block or anything like that :shock:

[jimfoo]

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:

[jtanguay]

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...

[Quantum TD]

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.

[jtanguay]

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.

[Quantum TD]

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.

[jimfoo]

Take video.  :lol:  :lol:

[Quantum TD]

Sting clankin away. Any chance it's the wrist pins?

[zukgod1]

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...

[Quantum TD]

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.

[jtanguay]

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!

[Smokey Eddy]

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!!!!!

[the caveman]

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.

[the caveman]

"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.

[jimbote]

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!!!!