Horrible Engine Noise- Only With Plugs In

[gijoe985]

I posted about this a while back, mixed in with other stuff, but our school shop DSM project has some issues.

When cranking the engine over, you heard some very unhappy internal engine noises. That said, they're almost nonexistent when there are no plugs installed. Or a compression gauge for that matter. But as soon as the cylinders have to build compression, you get very nasty noises. Sounds like thunking, grinding, stopping, nothing pretty. Anyway, we dropped the pan, found some minor bearing wear. Noticed that the one side of the thrust washer was significantly worn. The crank looked ok so we just slapped in new bearings. Put her back together and the problem remains the same. Aside from the bearings, everything looked ok on the inside. Well, that said, we're just trying to see if there is anything else to look for before we pull the motor.

 

[Boost-Junkie]

What did your compression readings look like? And have you pulled the valve cover to make sure nothing is loose making it noisy upon compression stroke

 

[chrysler kid]

How are you turning it over. Putting new bearings on a worn crank won't fix the problem of the crank being out of balance and will just make the problem worse.

I can't really help the problem with strange noises because all engines make noise.

 

[Boost-Junkie]

I don't believe an out of balance crank Will cause noise as opposed to a vibration. It's been parked for far too long shoot aft in the cylinders and oil maybe it will free up a dry component

 

[gijoe985]

So, we had almost perfect 150psi on all cylinders. Everything under the valve cover looks good. We've put oil in cylinders. I know that just replacing the bearings won't fix crank issues, it really was a hail mary on our part. We figured we'd give that a shot before pulling the motor. We've got a 6 bolt being rebuilt right now, so it isn't the end of the world, we thought we'd just try the quick fix.
That said, here's the video I did a while back. Whether a spark plug, or a compression tester, the engine seems to sound ok (maybe a bit of a rubbing noise) without anything in, but once a spark plug or compression tester is installed in a single cylinder, the sound of death comes.

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Again, if anyone has any suggestions before we just pull this thing and rebuild it, I'm all ears.

 

[Mauispyder]

I'd say it doesn't sound abnormal. Just like a 4g63 cranking with some compression resistance. I may be missing some nuances listening to this through my phone however.

 

[1990TSIAWDTALON]

That doesn't sound like any of the 4g63's I have had or been around...that "clunk, clunk, clunk" is not a good sound to me. Piston slop??? It almost sounded like a rod hitting the oil pan but surely that isn't what it is as it should do it under load or not.
Have you tried your Mechanics Stethoscope to try and pinpoint where it is coming from?

 

[Galipso]

i tried listening to your video a few times and can't really hear anything too odd other than the speed at which it turned over between the 2 tests.

Whats your history with the motor? Did you just rebuild it and put it back in? Have you ever had the car running?

 

[Mauispyder]

I'd go with what 1990TSIAWDTALON says, my hardware must be limiting what I can hear.

 

[97gsxIA]

That's a pretty loud/deep thunk for piston slap. Sounds like something rod related to me. You didn't mention which bearings you replaced. Mains AND rod? all hardware torqued correctly? You should have been able to at least see something out of the ordinary with the pan off. Forget a rod bearing perhaps?

You could try spinning it around once or twice with a plug in one of the cylinders, moving it from 1-4 to find which cylinder the thunk is coming from under load. Or spin it by hand to be safer.

BUT

Sitting there bumping the starter is just going to make it worse.

 

[gijoe985]

We replaced ALL the bearings and torqued things down. It did this before AND after we replaced the bearings. We hoped the bearings were going to fix the problem.

See a lot more details HERE- http://www.dsmtuners.com/threads/grandview-high-school-dsm-project.501329/#post-153574628

The sound is pretty much identical (a very loud and bad thunk, trust me, if you didn't hear it, it is bad) no matter what cylinder you place the tester in. I'm a high school shop teacher and I've never heard anything like it. My veteran mechanic buddy just swung by and agrees that is might be a broken piston slapping around. What's funny is that I have good compression.

We just started to pull it. Dropping in the 6 bolt. I'll come back and post once we find out what went wrong.

 

[blktalon3]

When you pull the plugs after you turn it over, were they damaged at all?
That sounds like something solid hitting something else solid.

 

[gijoe985]

Plugs were fine...

 

[chrysler kid]

How much end play did you have with the crank, did you check for typical signs of what is called crank walk.

If it's only making noise when it builds compression it could be a problem with the head.

There's only so much we can eliminate, if you have a backup engine and your are positive that all pieces on the head and bottom end have been triple checked on torque then I would add fuel and fire and see what noises it makes or if it even turns over.

Try turning the crank clockwise by hand with the plugs in to replicate conditions to make the noise. If you can make the noise by hand you've got a real problem. If you cant spin the crank by hand with a brake bar you might have dry bearings, I'm assuming you used assembly lube

 

[JPenny]

I'm sure this is a long shot. But my 97 gst was making a knocking noise. My first thought was in the head but with no avail after pulling valve cover I started to worry thinking maybe I spun a rod bearing. After removing oil pan and rod caps there was regular wear but things looked to be ok. long story short it ended up being my flywheel bolts had backed out enough to let the flywheel move side to side a little. I know this probably is not your case but mine did act the same way as far as no noise without compression/resistance.

 

[gijoe985]

I actually thought about that ^^^

 

[1990TSIAWDTALON]

My son had the same experience with his Automatic car. In his case, the flexplate had cracked. I don't know if you are a stick or auto but both the loose flywheel and a broken flexplate can make a similar sound. We pulled the motor out just to find 2 of the 4 webs were broken. New Kiggly flexplate and it was fixed. More food for thought....

 

[Boost-Junkie]

If it were an issue with a "broken piston" ? I'm assuming a damaged wrist pin, it would only be in one cylinder under compression not likely all 4 since you say it does not matter which cylinder the tester is in. Very possible cracked flex plate or backed off/broken bolts.

 

[gijoe985]

I'm leaning towards a broken/loose flywheel at this point. We'll find out soon!

 

[1990TSIAWDTALON]

I sure hope that is what it is so you can continue on with the project and it would be an easy fix. Good Luck!!!

 

[gijoe985]

Just an FYI, got the engine pulled today and the flywheel looked fine.. so we shall see...

 

[1990TSIAWDTALON]

Very curious what the sound ends up coming from...