possible severe engine damage - would appreciate diagnostic advice

[seningen]

Originally Posted by Maxodus

Could be many reasons but from my experience, and knowing this is the "S" model engine, i'm putting my money on a broken valve spring.

Good luck with the diagnosis and report back if you can!

I'm all for more knowledge -- my questions are not questioning your opinion
just seeking more information:

What experiences have you had with broken valve springs?

What is the sound like on an M96 engine?

Why is the "S" a factor in your decision.

thanks,

mike

[Fluellen]

Thanks, everyone, for the helpful suggestions; I appreciate them!

My work schedule hasn't allowed me to do any further investigation, but I hope to be able to spend some time on this on the weekend. I will report back and update.

BTW, no trouble codes stored...

FWIW, broken valve spring was the first thing that came to my mind as well... but this needs further investigation...

[Fluellen]

Update:

I drained the oil and filtered it through a washcloth. No foreign particles. No intermix. Removed the filter and cut it open - nothing. Looks exactly like the previous three filters I cut open.

Re-filled with Rotella 5W40 (same as before; last oil change 5 months / 1 Kmi ago) and started it. Smooth idle, no noises.

I haven't checked for noises above-idle yet (all engine covers are off, and the motor gets quite loud when you go >1500 rpm).

I guess I'll look at the spark plugs tomorrow, just in case.

Is it possible for a valve spring to be broken, and you can't hear it at idle?

[seningen]

Were you low on oil?

You might have had a weak lifter or hearing chain noise

All hard to tell without knowing what it sounded like.

Mike

Originally Posted by Fluellen

Update:

I drained the oil and filtered it through a washcloth. No foreign particles. No intermix. Removed the filter and cut it open - nothing. Looks exactly like the previous three filters I cut open.

Re-filled with Rotella 5W40 (same as before; last oil change 5 months / 1 Kmi ago) and started it. Smooth idle, no noises.

I haven't checked for noises above-idle yet (all engine covers are off, and the motor gets quite loud when you go >1500 rpm).

I guess I'll look at the spark plugs tomorrow, just in case.

Is it possible for a valve spring to be broken, and you can't hear it at idle?

[Jaxonalden]

At idle I don"t think you'll hear it, idle should be normal being it's a four valve set up. Remember, if it is a broken spring, the chances of dropping that valve increase significantly with greater RPM because it will float a whole lot sooner. You might want to pull the valve covers and do a look see first.

[Topless]

Originally Posted by seningen

I'm all for more knowledge

What experiences have you had with broken valve springs?

What is the sound like on an M96 engine?

I have seen a handful of broken valve springs including a few M96.

Common symptoms:
Top end clatter rising with RPM, one fouled cyl, no debri in oil pan, possible backfire. A reasonably easy fix if you catch it early.

[Maxodus]

Originally Posted by seningen

I'm all for more knowledge -- my questions are not questioning your opinion
just seeking more information:

What experiences have you had with broken valve springs?

What is the sound like on an M96 engine?

Why is the "S" a factor in your decision.

thanks,

mike

Yeah sorry i forgot to elaborate - it's a friend of mine, who has a 2003 S model that exhibited the same symptoms. It's definitely weak having only one data point, but sometimes i just go with my gut feelings~

[seningen]

Originally Posted by Maxodus

Yeah sorry i forgot to elaborate - it's a friend of mine, who has a 2003 S model that exhibited the same symptoms. It's definitely weak having only one data point, but sometimes i just go with my gut feelings~

My mech/shop partner is deaf but is very skilled rebuilding M96 engines

I help out by being his ears, i have not had the chance to hear a broken valve spring before.

Mike

[Lil bastard]

If I'm reading this correctly, the OP has now turned the motor over a 3rd time at least.

If you keep doing that, the sympathy quotient is going to rapidly drop to ZERO!

These are expensive motors. Until you have a competent, qualified person look it over, leave it be. For your own sake!

Good luck!

Cheers!

[Fluellen]

Another update.

Spark plugs looked okay, albeit a bit sooty for my taste. 19 Kmi / 3.5 years on the plugs. Perhaps I need to look into the O2 sensors...

Plug #1 was noticeably loose, perhaps barely hand tight. My hypothesis is that this plug was never installed tight enough and loosened due the recent extremely cold outdoor temperatures around here. This perhaps could explain the clattering.

Compression test yielded good consistent numbers (>140) across all cylinders.

I installed new spark plugs and started the car. Smooth idle. Slowly reving up to 2500 rpm, there were no noises.

I can't do a road test at this time, because I discovered that my rear axle boots are torn and need to be replaced. They were fine four months ago; perhaps also a victim of the cold temperatures.

For now, I am hopeful that this could be the happy ending to this story... we'll see.

Thank you, everyone, for your helpful advice and suggestions!

[Fluellen]

Originally Posted by Lil bastard

If I'm reading this correctly, the OP has now turned the motor over a 3rd time at least.

If you keep doing that, the sympathy quotient is going to rapidly drop to ZERO!

These are expensive motors. Until you have a competent, qualified person look it over, leave it be. For your own sake!

Good luck!

Cheers!

I agree that the first restart after the noise was reckless. No doubt about it. Subsequently, however, I think I took reasonable, calculated risks.

But it perhaps doesn't make much sense to discuss individual risk perceptions. I started this thread to ask for diagnostic advice. What would have been the diagnostic plan that a competent, qualified person would have followed?

[Dale_K]

The compression numbers certainly seem to be a good sign. Kind of rules out piston/valve contact. Did you figure out where the oil leak is coming from?

[Jake Raby]

The M96 is known for broken valve springs.. That could be the issue. A compression test and leakdown test would be the first diagnostic that I'd carry out.