Loud Knocking! Possible Flex Plate Issue

dan_j_b · #1 10-12-2004, 06:33 PM

I have recently reinstalled my engine after a complete teardown, inspection and gasket/ring replacement. After I rebuilt my engine and installed it the first time, there were no strange noises at all. It sounded great all through break in, but I had to pull it back out to replace the rear main seal, front crank seal and cam seals (stupid me put them in backwards). Then I put the engine in a second time and a minute or two after startup, it started making a loud knocking sound (so loud I can't bring myself to let it run like that for more than a few seconds at a time)!

I read some posts on here about people who have had problems with flex plates breaking after being reinstalled (something about allignment). So I pulled the motor for the third time tonight and the flex plate appears to be fine!

Should I continue blaming the flex plate or should I investigate something more internal? The only other difference with the second time I installed it was I switched it from regular oil (for break in) to Mobil 1 5W30. Could it be that the synthetic oil is causing a hydraulic valve adjuster to stick or something?

Any quick help would be appreciated!

Thanks
Dan

NikFu S. · #2 10-12-2004, 07:22 PM

Loud knocking can mean many things. I'm assuming you are hearingit from dead center of the engine compartment?
It is very likely to be sticky valves. I had the same problem and it only cleared up after running for a long while with some detergents.
Try that first if you are fairly sure it's not a predet ping.

dan_j_b · #3 10-12-2004, 07:32 PM

What additive worked for you? do you run synthetic oil or not?

dan_j_b · #4 10-12-2004, 07:39 PM

I have a feeling it could be the valve lash adjusters. I didn't store them in oil when I had them out for like a month. If so, whats the best plan of attack? should I let it sit and hope they loosen up, or start it and run it until it goes away?

NikFu S. · #5 10-12-2004, 07:50 PM

I don't know what's in there now as I didn't do the last change, but I usually run 5W-30 Castrol Syntec, and when I heard the clicking I dropped in some Techron f.i. cleaner and some octane booster, because octane ratings just dropped up here in Alaska.

Oh yeah I also dropped some Marvel into the oil.
Clicking stopped after about 10 miles.
It came back later on, but it went away for good after another dose.

Just go for the simplest solution for the time being until you can be positive what's wrong. It very well might just go away.

dan_j_b · #6 10-12-2004, 07:54 PM

I'm going to look the flex plate over real close and then put the engine back in tonight. Tomorow I"ll add some Marvel stuff and run it for a little while and see if it clears up

Thanks
Dan

dan_j_b · #7 10-12-2004, 10:19 PM

SHES DEAD!

I started it back up and ran it for about 20 seconds and reved it up and the engine shook violently and after I turned it off I turned the crank a little and heard something metal fall inside. So much for that idea. Big fat waste of money...

NikFu S. · #8 10-13-2004, 02:03 AM

Only about 20 seconds?
My friend, something like this would have been impossible to diagnose without tearing the engine apart again and inspecting every moving part.
About how high did you rev?

I just wish someone else had some input on this.
I have no idea what would shake the engine so hard.
It's possible your pistons (at least one) are trying to get out.

I think you know this by now, but looking again at how loud you described it was, the only logical explanation is something was banging into something else.

Hopefully the block is not damaged.

This is obviously causing too much trouble for you.

One suggestion: turn the crank again, to see if it makes this "something falling" noise again. Listen for what specific area of the engine it seems to originate. Then the trouble will be apparent.

Good luck with it.

svxistentialist · #9 10-13-2004, 02:37 AM

Sorry to hear this man.

My black car has terribly noisy clicking in the engine. My bet is flex plate, but I will not know till strip-down.

It runs, but the noise is painful to listen to. It's possible it also has a sticking valve, as it's been lying up.

Yours sounds more like a con rod or something. Are you sure you put back on the timing pulleys in the correct place? Hard to know how it would break when you have just stripped it.

Hope it's not too expensive.

Joe

dan_j_b · #10 10-13-2004, 06:54 AM

Quote:

Yours sounds more like a con rod or something. Are you sure you put back on the timing pulleys in the correct place? Hard to know how it would break when you have just stripped it.

Yeah it is definately something like a rod that broke. I know the cam gears and pulleys are right because for one, I didn't take the cams of between the time it ran perfect and now. Second of all if I would have gotten the belt on wrong or something, that would have caused it to just run funny, not break anything (non interference with pistons). Unfortunately I don't have the time or money to pursue it further at this time.

I also switched it over to mobil one after I had the engine out to replace those seals. Prior to that, I ran it for about 15 min at 3k RPM to break it in. Would have ran it longer the first time but the rear main was spilling oil all over. It ran perfect during that break in period, too.

Gotta get to work

dan_j_b · #11 05-26-2005, 06:32 PM

I took the motor apart today and I think I found the source of the noise. My guess is I either didn't get all the main caps tight enough or a wrist pin clip came out. Luckily, although the spark plug was smashed flat, the valves and head otherwise looks perfect. So I guess I am shopping around for a short block assembly. Anyone have one in the Sioux Falls area?

mbtoloczko · #12 05-26-2005, 07:47 PM

Now that's munched. Tragic, but kinda interesting looking. Hope things go better for the next rebuild.

NikFu S. · #13 05-26-2005, 10:13 PM

It just shattered like glass...

UberRoo · #14 05-27-2005, 02:59 AM

Quote:

Originally Posted by dan_j_b

I took the motor apart today and I think I found the source of the noise. My guess is I either didn't get all the main caps tight enough or a wrist pin clip came out. Luckily, although the spark plug was smashed flat, the valves and head otherwise looks perfect. So I guess I am shopping around for a short block assembly. Anyone have one in the Sioux Falls area?

I reckon you got it on the first guess, except I think you meant 'rod caps.' In the pictures, the cap bolt on the right looks fatigued where it broke. The threads on the left cap bolt are a bit chewed up, but no apparent stress marks. On the rod's crank bearing race, both sides of the race are broken off, but one side looks like a fatigue failure while the other side appears to be yield failure.

I speculate that one nut worked it's way off the [left] rod bolt. The [right] side of the bearing race held on as long as it could, flexing back and forth, which caused the wear marks on the threads of the [left] rod bolt which no longer had a nut to stop movement. The [right] rod bolt and [right] half of the bearing race flexed until the metal fatigued and failed, leaving the clean break characteristic of a brittle alloy. The bearing race of the rod, being aluminum, probably failed right away, but was held together by the rod bolt until it also failed in the only place it could flex: where the bearing race had previously failed. When the [right] side failed, the cap simply slid off the [left] bolt, which appears to be pressed in, and functions more like a stud. In this scenario, the other half of the broken bearing race was sheared off on the next revolution of the crankshaft as the remaining cap struck the stationary rod, still protruding from the bottom of the cylinder. This explains the bent rod and deep scarring of the [left] failure point. Alternatively, the cap did not simply slide off, but rather came off in a twisting motion, causing the [left] half of the bearing race to fail instantly. The bent rod and scarring would have happened on subsequent passes of the crankshaft.

...at least that's what I think happened. Did you see anything that reinforces or diminishes my theory?

Anyway, sorry about the luck. Sometimes dotting your T's and crossing your I's can be as dramatic as throwing a monkey wrench into the works.

dan_j_b · #15 05-28-2005, 11:06 AM

Yeah that sounds like a good theory to me. I'll let the real experts deliberate over the exact details. I'm just going to put that whole thing behind me and swap in a diffrent used shortblock. Yeah I meant rod caps, not main caps. It looks like the shape of the piston saved the head. It smashed the spark plug flat, but doesn't look like it touched the valves. I'll have the head checked out by a machine shop before I reuse it, but I think it looks fine.