Sporty

Your Indy should have a scope- have him look at with his quailfied / perspective eyes - why wait to do it on your own at that point?

bgoetz

I am just taking the filter to him. I would need to trailer the car if I was going to have him take a look.

bgoetz

The challenge with this is what steps can I take to investigate this to make a “go/no go” on a rebuild? It seems like this would have to be diagnosed by opening the engine up, so at that point I am already into “rebuild mode” especially if it is going to go to Jake or RND.

The sound definitely goes away after 2.5k. I think I should follow a process of investigation that eliminates scoring or major internal failure first, which is what I think you are advocating.

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sandwedge

Kind of what I'm thinking too. This guessing game could go on forever while according to bgoetz the car isn't driveable.

First of all, really sorry to hear what you're dealing with. How much of a do it yourself type are you? The consensus here seems to be that it won't be a simple fix no matter what's going on. So unless you're equipped and comfortable to get into the engine if that's what it comes to, why not flatbed it to your indy and get a professional diagnosis and an estimate for the repair? Wouldn't that provide some kind of relief of knowing what you're up against instead of this day by day maybe this, maybe that?

bgoetz

I am fairly handy with cars and could easily swap out an engine. My brother in law has a shop and a nice lift. My goal is to try to figure out if I am dealing with a rebuild situation before doing anything with the car. From there I can decide the course of action because that might not involve the car going to my indy. If we can’t conclusively determine if it needs rebuilt then yes it will be trailered up to him.

If there is crap in the filter it is pretty much a stop point because then we know it is internal damage. I might drop the sump at that point to get a better idea of just how bad it is and if it might impact a rebuild budget.

Fullyield

Should probably drop the sump anyway to do a proper bore scope. See Jake Raby’s videos which are great. Isolate sound to specific cylinders Scope upper cylinder from plug hole with piston at BDC but still cannot see bottom of cylinder walls. So, drop sump and scope bottom of cylinder with piston at TDC. Jake shows how it is done. Best wishes.

Optionman1

If you have access to a shop and a lift I think dropping the sump and doing a complete bore scoping would be the step that would be most revealing. Not sure why a car suddenly produces the piston slap noise out of nowhere. Have never heard an explanation of what physically changes in that moment but something must happen. Best of luck and I will be following along.

Fullyield

Agree with understanding that you first used a Steelman Electronic Ear first to isolate sound to cylinders and rule out noise/knock coming from a pump, pulley or bearing.

Optionman1

Just came across this in a 996 thread and thought it couldn't hurt to copy it here:

You are correct in that "most " rod bearing failures on common engines have that deep knock sound, but M96/7 engines have a really tight clearance from the piston crown to the head quench area.

So much so that any carbon build-up in the piston crown of over 1mm can also lead to a sound like "piston slap".. Case in point a Rennlister here (3/98 911 Coupe ) had a knock that everyone assumed was a bore-score/piston-slap, I suggested he do a de-carbon of the pistons and TexSquirrel did it ( thread in here for some if interested) and it totally stopped the knock.

I went over to the 986 forum and looked/listened to the video/audio, that engine with only 5 psi oil pressure and that sound for sure has a failed rod bearing.

This was posted by @Porschetech3 who is an expert.

sandwedge

With your resources and your DIY capabilities I understand now why and how you're going about this the way you are. I would do the same if in your position. Good luck. Hope what you eventually find out is better news than some of the worst case scenarios mentioned in this thread.

bgoetz

Small update. I drained a bit of oil to grab a sample and look at the magnetic drain plug and also pulled the filter. The drain plug clean minus the typical small amount of sludge it collects. The oil looked mostly clean with only a couple of small aluminum flakes. Based on the sound the engine is making I would expect to see more metal, but I will know more this afternoon when we cut open the filter.

Right now I am still considering something as simple as a hydraulic chain tensioner failing. I was occasionally getting chain slap on startup and it actually started to happen more frequently. I think a chain tensioner could also result in a little aluminum from the chain slapping the case. But again hopefully the filter will tell us a bit more.

rtl5009

Pics of debris?

bgoetz

They were really so few and so tiny that I am not sure it would have shown well. Like 10-20 pin head size bits of silver glitter. Maybe even smaller.

G.I.G.

Any chance you can drop the sump at your house? That will give you a clear view of the bottom of the cylinders and might paint a more accurate picture of what is going on. According to the experts, that is where scoring begins.

I suspect most, if not all of our cars with 30k or 40k plus miles have some degree of "streaking" or "scuffing", but full on scoring is hard to miss if you're looking at the cylinder from the bottom with the sump removed.