Avec

I needed to change plugs and coils, and investigate a new engine tick I noticed over last weekend. So, while there, I did a compression test.

First, all coils were uncracked and all plugs appeared the the same. No unusual oil or anything else between plugs.

Compression Test Results

Cyl Dry Wet
#1 190 235
#2 193 238
#3 192 248
#4 152 242
#5 195 260
#6 198 240
#7 195 250
#8 198 262

At the upper end, the wet readings were more approximates due to the limited granularity on the gauge. Anyway, I think I found the source of by engine tick. Needless to say, I am pretty pissed

19psi

That sucks. At least it made it 100K more miles than most.
Did you guys get those -30º temperatures a few months back? I didn't dare start mine during that time.

oldskewel

Avec, really sorry to hear that. Are you going to do a borescope to confirm?

Is there anything else that could be causing that?

Avec

Yes, we did have the bitter cold, and this is about the only thing I can think caused it. I used 0w-30 full-synth oil, but at that temp, it would be like caramel sauce. I did let it warm up 5-10 minutes before driving, and am pretty religious about keeping RPM low until engine warms. I actually go to manual mode and shift as soon as it will allow me to.

I have not done a bore scope yet. To do it myself, do I need to drop the pan?

v10rick

Scoring begins below the piston skirt. In the later stages its above the piston which you can view with the spark plugs removed.

This would be one the first reports of scoring, without oil on the spark plugs or excessive oil consumption.

Vivid7

Was it garaged or does it sit outside?

Avec

Just so I understand, are you saying it is either an anomaly or it could be something else?

Last weekend I was on a total of about a 900 mile run around the midwest. I noticed the louder than normal tick. I had checked the oil prior to the run and again after. No consumption. This lead to me think a valve issue and put in some SeaFoam, which I had used on my BMW previously and had great success unsticking a chain tensioner. I have run it about 200 miles with the SeaFoam and no change.

I could re-run a compression test, but I still have the knocking / ticking that is new and loud enough to hear in the cabin, even with radio on (very low, background sound volume) The dry / wet numbers do point to rings, whatever the cause. To test further, what should I look for or test?

Thanks for the input

19psi

If you have the noise and low compression, the damage will be seen through the spark plug hole. Bringing up compression by adding oil to the cylinder is a ring/cylinder issue. Nothing points to a valve or cam chain. Best hope would be a stuck ring in cylinder 4, but I don't think that would cause knocking so loud you could hear it inside the cabin.

I'd stick a camera in cylinder 4. Those borescopes that plug into a laptop or phone can be bought for $15 off Amazon. I never checked a cylinder with mine, but it does work amazingly well. They come with little clip on mirrors which you'd probably need to use for the side view of the walls.

v10rick

This^^^

oldskewel

If you don't already have a borescope / endoscope, given the importance of this test, I'd make sure you get a good one. I have a cheap one I got off eBay or amazon, and wish I had got a better one off eBay or amazon. They're not all the same in terms of resolution and illumination. I did my testing using the one I already had, saw nothing, and things are still good, but doing the test again, I wish I had bought a better scope.

Yes, just focus on cylinder #4. Rotate the engine so the #4 piston is at its lowest point, and look in there, and hope for the best.

True that the scoring seems to start at the bottom of the cylinder wall, which is covered by the piston, even in its lowest position. So it could be that you look in there, with perfect visibility, and see no scoring, even though scoring exists hidden below the piston top.

So consider the visual test to be one that will confirm scoring, but cannot rule it out.

And it is claimed to be possible, although top secret, to view the cylinders from below. I think the engine builders figured out how to do that.

19psi

If the scoring was hidden below the rings, there would be no compression issue and no noise.

The only reason to spend hours of labor dropping an oil pan to check the lower end would be during a pre purchase inspection...when there are no signs/symptoms of scoring but it's in the beginning stages of happening.
As far as being able to do it without dropping the oil pan...until someone can provide a how to with photos or video, it never happened.

deilenberger

I've always found that story improbable given the design of the V8 semi-dry sump.