Engine self-destruct

Zolll · Post by **Zolll** » 04 Jun 2021, 06:17

Hi, my 2004 XC70 with 172k miles developed a sudden misfire and intermittent knocking 15 seconds before getting home. Code reader indicated a misfire on cylinder 4. I pulled the spark plug and noticed that the electrode was bent against the tip and some of the carbon deposit had been scrapped off the plug. Scoped the cylinder to find 3 small crushed metal pieces and the top of the piston completely shiny/peppered. Your opinion on what could've caused this is welcome! I currently suspect that the engine sucked-in the PCV banjo bolt ball bearing (replaced 4 years ago).

I cranked the engine with spark plugs removed and it sounded just fine, but with plugs, it was like having a golf ball in a cylinder - Now, the difficult question, the extent of damage - I am almost certain that there is some valve injury and I could probably handle fixing that. For the smart folks here, what are the chances that the piston/rods/crank is damaged? The engine was running super strong before that - wondering if it's worth pulling the head off to replace bent valve.

I appreciate your feedback and past experiences..

darylrobert · Post by **darylrobert** » 04 Jun 2021, 06:41

i heard about that ball bearing. Did you have the updated part fitted Volvo 31325709

www.matthewsvolvosite.com/forums/viewto ... 7&start=20

Zolll · Post by **Zolll** » 04 Jun 2021, 07:32

Hi - I'm not sure which version of the bolt I received when I ordered the parts. I had ordered all of the PCV parts from an online outfit at the time.

Post by **volvolugnut** » 04 Jun 2021, 08:24

Can you get a camera in that cylinder and look around, especially at the valves? You might have a chunk out of a valve.

volvolugnut

Zolll · Post by **Zolll** » 04 Jun 2021, 08:57

My scope won't look up towards the valve and the tiny mirror that came with the camera can't be found.. Your comment made me think that the hardened bearing would've won against the softer valve, and what I'm seeing are pieces of valve... I'll try to vacuum out the pieces and start it for a second. I might just as well pull the head and take a good look at it.

Post by **volvolugnut** » 04 Jun 2021, 09:35

Try to trap the pieces as they get vacuumed. You will want to try to determine what they are. But you knew that.
volvolugnut

Zolll · Post by **Zolll** » 04 Jun 2021, 13:27

Here is what I got out with a small magnet... The misfire is still there but the loud noise is gone..

Post by **jonesg** » 04 Jun 2021, 15:26

A leakdown test will probably show intake and exh valves are leaking.
This guy went through the same thing, I think he found it cheaper to swap a used engine in.

Post by **matthew1** » 04 Jun 2021, 15:56

Zolll wrote: ↑04 Jun 2021, 13:27 Here is what I got out with a small magnet... The misfire is still there but the loud noise is gone..

Volvo.jpg

Looks like a 22 caliber. You been taking fire recently?

Post by **jonesg** » 04 Jun 2021, 16:22

the check valve is a slug, not a round ball as most say.