07 XC70 marble in the engine

[erikv11]

Wife was driving it slowly in town, suddenly the engine got “rough almost like when the valve burned in the 850.” Finished driving it the two blocks to home and it’s been parked since, which has been a few days, until today when I looked at it.

When I start it up the engine clacks randomly or rhythmically or not at all, as in the video. When rhythmic it goes up and down with rpm’s. Sounds like coming from the top end, top and toward the passenger side. Oil level is fine. Timing path appears fine. After a few startups it threw a cylinder 3 misfire code, nothing else so far.



What next, any suggestions? Unplug the VVT solenoids see if that affects it?

Likely a Volvo mechanic could diagnose this in a few seconds, maybe I’ll take it by the Indy if driving it isn’t deemed idiotic.

[jonesg]

a stethoscope will pinpoint it.

[dikidera]

Pour a very small cup of water on the serpentine belt while running and report back. Pour slowly over Ps pump pulley.

[abscate]

It doesn’t sound clingy enough for expensive bottom end stuff. Stethoscope it or maybe take off serp belt.

I would drive that for 5-10 miles at 30 mph after a burnt offering to the Norse Gods

[erikv11]

Went back to check with stethoscope and a mister for the serp belt. But it Wouldn’t make the noise, just had a rough idle. So I went down the line and pulled each injector. Every one of them affected idle except for number three. So number three is not firing. Pull number three plug, the electrode gap is smashed and the prong shows some scarring from getting hit. Here’s the plug.

Smashed plug

Checked compression on 1-2-3 got 125-130-55. Checked each cylinder twice those are averages.

Do I stop now or try to do more troubleshooting? Seems the bottom end is in trouble given that plug damage? I could see then top of the piston in the plug hole, it looked fine there of course. Borescope time maybe; I don’t have one.

[abscate]

She has dropped a valve and has some bits in the cylinder.

Off with her head!!!

[erikv11]

Sigh. I do always preach that an engine swap is a better move than head work ...

[abscate]

Depends on condition of engine and accessories. Labor wise , about the same

Cylinder head job requires hood local shop

Erik , bottom end is fine because she drives like an adult and Babied it home.

[erikv11]

I was referring to possible piston damage from whatever smashed the plug, that's all.

I do have a good local shop. Been 10 years since they did a head for me though.

[abscate]

You will know when it opens up. But it’s it’s got 55 psi it isn’t catastrophic