What is this noise?

kwoolard · Nov 15, 2009

1999 5.7L Mercrsuier - Alpha Gen II

History:
The last time my boat has been run in the water was early Sept. Engine has ran great since I've owned it, only minor issues that have been resolved. Since Sept. I've haven't had the time to take it out on the water so I usually will run it on the muffs once a week or every other week. Last time it was ran on the muffs was last weekend and the engine ran great, no noises at all and a smooth idle at 1500 rpms.

Today's problem:
I started the engine on the muffs and instantly had this loud sharp clacking noise that sounded like something hitting the oil pan. I immediately shut it down, engine maybe ran for 3 or 4 seconds. I've fortunately never had to hear what a blown motor or broken piston rod, etc sounds like so I don't know what the problem is. I then turned the water back on and fired it up again with the same noise, engine ran like crap and backfired through the carburetor and I shut it off immediately.

I don't know what this noise is but it is LOUD and has me worried something internally has broken apart.

A buddy of mine said that it is probably the lifters and I should run it a little longer to see if it gets better, but this noise has me paranoid and I'm afraid if I do it will damage something.

Anybody have an idea as to what this could be? Do lifters drain down like that and cause such a loud noise in the oil pan?

Thanks!

Gary H NC · Nov 15, 2009

Re: What is this noise?

Lifters are more of a clicking noise.
Was the drive raised up? If not it sounds like something let go in the engine...

Capt'n Chris · Nov 15, 2009

Re: What is this noise?

Disconnect the battery, pull the plugs out, take it out of gear, turn the fly wheel by hand and listen for anything odd and if it is coming from the powerhead. If you don't hear of feel anything there, put it in gear and turn the prop a bit and listen for anything in the gearcase. This won't solve anything, but may give you an idea if anything might be binding.

kwoolard · Nov 15, 2009

Re: What is this noise?

The drive was down.....I never run it with the drive up.

At first I thought it might have been hydrolocked, but I didn't think it would start up after that.

Should I run it one more time to see if the noise goes away, or should I start the disassembling process?

If it was something internal such as a rod, I should be able to take the plugs out and turn it over by hand to see if the noise is still there. Or I could ground the coil lead and just crank it to see if the noise is still there.

??????

v8power · Nov 15, 2009

Re: What is this noise?

backfiring yhrough the carb and running like crap? Sounds like it mave have a stuck valve, or maybe a whiped lobe on the the cam, or a broken rocker arm. pull the valve covers off and crank the engine over with the coil unplugged and check to be sure all the rockers are moving and that none are loose or broken.

kwoolard · Nov 15, 2009

Re: What is this noise?

I'll pull the valve covers tomorrow and look and feel for anything.....I think I can pull those off without having to take the exhaust manifolds off. Everything else suggested will require the exhaust manifold to come off, even to just take the plugs out!!

So everybody agrees, NOT to run it again to see if it is a lifter that has collapsed or bled down?

v8power · Nov 15, 2009

Re: What is this noise?

running it again isnt a good idea. if you start it often the lifters wont bleed down that much. if a lifter collapsed you will be able to find it when you pull the valve covers. if you find a rocker that is extremely loose, and the rocker and nut are not loose, you may have a collapsed lifter. but rockers will fail more often than lifters.

kwoolard · Nov 15, 2009

Re: What is this noise?

alright

just strange that it's been running great and then all of a sudden, sounds like a monkey beating a wrench inside the engine

v8power · Nov 15, 2009

Re: What is this noise?

a valve stuck open even just a little can cause a miss, a backfire, and the monkey with the wrench to. hopefully you will find what is making the noise when you pull the covers off. let us know what u find and good luck.

kwoolard · Nov 16, 2009

Re: What is this noise?

Talked with a mechanic buddy of mine who is pretty sure it is a lifter not pumping up. We ran it for about 25 seconds or so and I videotaped it.

Engine Noise

He said I could run some MM oil or Lucas to help free it up, and that running it on the muffs wouldn't hurt it.

What do you guys think from listening to the video?

I'm leaning towards taking the valve covers off, I'd really hate to run it not knowing if it could be a dropped valve or not.

Gary H NC · Nov 16, 2009

Re: What is this noise?

I would be pulling valve covers...that is pretty darn loud to be a lifter not pumping up.

kwoolard · Nov 16, 2009

Re: What is this noise?

I know its hard to say, but do you also feel like it is valve train noise and not the rotating assembly?

Gary H NC · Nov 16, 2009

Re: What is this noise?

Hard to tell from the video on my laptop but it sounds more valve train related to me.

Grumman59 · Nov 16, 2009

Re: What is this noise?

Sounds to me that the knock is at engine speed frequency. A lifter knock would be at half engine speed.

That's a heavy knock for a lifter, too. Could be a rod bearing. How was the oil pressure?

kwoolard · Nov 16, 2009

Re: What is this noise?

Oil pressure was at 40 psi.

Took the starboard valve cover off, luckily it would come off without removing the exhaust manifolds. No signs of damage to any rocker arms, valves, keepers, springs or push rods. Rockers feel tight, there are a few pushrods that I can rotate by hand, but no up and down movement.

Is there anything specific that I should be looking for that would indicate a collapsed lifter?

Port side requires removing either the remote oil filter bracket and/or the power steering pump lines. I'll tackle that tomorrow night.

As for the frequency of the sound i've tried counting the number of ticks and it seems like it is at half the engine speed, but I could be wrong. I was running at most 1000 rpms and as little as 500.

I'll post more tomorrow.

wire2 · Nov 16, 2009

Re: What is this noise?

That *could* be as simple as an exhaust leak. I run double wall stainless headers, and occasionally I forget to tighten the bolts soon enough. When one of the gaskets blows out, it sounds a lot like a serious knock.

kwoolard · Nov 16, 2009

Re: What is this noise?

wire2 said:
That *could* be as simple as an exhaust leak. I run double wall stainless headers, and occasionally I forget to tighten the bolts soon enough. When one of the gaskets blows out, it sounds a lot like a serious knock.

I dunno, sounds too loud and too much like metal on metal to me. If I don't see anything in the port side valve train I'll be pulling the exhaust manifolds, guess I'll see if that is the problem then.

v8power · Nov 16, 2009

Re: What is this noise?

definetly pull the other valve cover, also rotate the engine by hand when checking the rockers and pushrods, to be sure the lifter is on the heel of the cam. you may not find one loose if it is up on the lobe. i had a 350 chevy wipe a lobe and make a similar sound but could not find a loose rocker until i rotated it around a couple times. if a lifter was collapsed you would feel it all the time.also it only takes a few seconds for a dry lifter to pump up.

v8power · Nov 16, 2009

Re: What is this noise?

you may want to use a stethoscope or a long screwdriver to determine where the sound is coming from. that way your not taking everything apart to find it.

kwoolard · Nov 16, 2009

Re: What is this noise?

it's a little too late for that i guess, i've got closed cooling and heat exchanger and accompanying hoses had to come off to get at the port cover, not to mention the power remote oil filter which will come off tomorrow.

I was going to take my buddy's advice and just run it to on the muffs a few minutes to see if it went away, but that noise is just too loud and my paranoid ear couldn't stand it much longer.

If it was a wiped lobed, wouldn't I have some warning signs? This problem started all of a sudden......shut the motor off last weekend and started it up yesterday with this noise instantly.

The only other thing that comes to mind to cause instant damage is hydrolock. Could a small amount of water get in and be enough to start an engine unoticeably and bend a piston rod or spin a bearing?

What is this noise?

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