THE M3 IS GETTING THE ANRI BUILD TREATMENT - Blown headgasket to build thread

[ChapterM3]

You need to get a second opinion, seeing these leak down numbers compared to the compression numbers I don't trust either considering your driving observation. 35% on its on is a huge number and for the (4) "good" cylinders to be at that, IDK, I would be skeptical.

Wooah, yeah +1 to second opinion. Like George, I don't trust those numbers after seeing that the shop called 35% "good".

Thank you guys for your input - I woke up today thinking something is off: 35% leak down and those cylinders are still making ~170psi compression? Even 70% and still 120 psi compression test? That would mean that 70psi is leaking somewhere (from the 100psi leakdown) and yet the car still makes 120 psi in the compression test, I'm no mathematician but how does that add up?

I've been reading that around 5% leak down is considered normal, would you say that's accurate?

[ChapterM3]

I just pulled this out of my engine a couple weeks ago. Car had no misfires or drivability concerns. Only indications that something was wrong were low dyno numbers (~30hp down from similar setups) and when I did a compression test everything was at 165psi except for cylinder 5 which came in at 145psi.
I don’t mean to scare you, just showing that sometimes bigger issues might not cause a misfire condition.

Damn. First of all, sorry to hear that about your motor, that sucks. I appreciate your input and yeah, I would be shocked if that was my case, but always good to remember that sometimes things break without warning. I hope you get your car back together and running again soon!

[heinzboehmer]

Wooah, yeah +1 to second opinion. Like George, I don't trust those numbers after seeing that the shop called 35% "good".

[George Hill]

You need to get a second opinion, seeing these leak down numbers compared to the compression numbers I don't trust either considering your driving observation. 35% on its on is a huge number and for the (4) "good" cylinders to be at that, IDK, I would be skeptical.

[Ryan_R]

That is something that I can't get out of my head as well - wouldn't the misfires happen even while driving and the car wouldn't drive as well as it does? Driving the car back from the shop it again made me think about this point again: the car seems to be running well, sounds amazing and there are no hiccups or stumbles in the RPM range. With apparently 70% leakdown in both 5 and 6, how can that be? I would imagine the engine running much rougher than it is

I just pulled this out of my engine a couple weeks ago. Car had no misfires or drivability concerns. Only indications that something was wrong were low dyno numbers (~30hp down from similar setups) and when I did a compression test everything was at 165psi except for cylinder 5 which came in at 145psi.
I don’t mean to scare you, just showing that sometimes bigger issues might not cause a misfire condition.

[ChapterM3]

discoelk - Good points you raise - a blackstone oil analysis showed no signs of any head gasket material or coolant remnants in the last 10k miles, but yes as JayJaya said, it seems like it's between cylinders 5 and 6. The car is not being driven or run until I have an idea on next steps, which for me as of now is getting a second opinion on the compression test and leak-down test, which I may end up doing myself with some help

[discoelk]

The head gasket failure is between 2 cylinders, not between cylinder and oil passage or coolant passage. The only way to test for this is via a leak down test.

You could try using a borescope with a 90 degree camera to try and see if theres any visible damage to the head gasket. Maybe shining a bright light into cyl 6 while bore scoping cyl 5 would show it.

Good point. Total brain fart.

[jayjaya29]

The head gasket failure is between 2 cylinders, not between cylinder and oil passage or coolant passage. The only way to test for this is via a leak down test.

You could try using a borescope with a 90 degree camera to try and see if theres any visible damage to the head gasket. Maybe shining a bright light into cyl 6 while bore scoping cyl 5 would show it.

[discoelk]

Just FYI, misfire is typically calculated based on (lack of) crankshaft acceleration. Given the firing order of the S54, 1-5-3-6-2-4, it's entirely possible that the ECU will throw a code for misfire on cylinders that don't have misfire. I believe this is what sapote is getting at above.

Cylinder 3 misfire code doesn't provide any evidence against a blown head gasket. Keep in mind that you're doing further damage to the head and block if the head gasket is blown by continuing to drive the car. Maybe I've missed it but has anyone suggested looking at the coolant or testing it for combustion gasses?

[ChapterM3]

Yeah, take your time and do a careful leak down test, and hopefully no leak. I still don't quite understand that a bad head gasket that only caused misfire at idle but perfectly fine during driving.

That is something that I can't get out of my head as well - wouldn't the misfires happen even while driving and the car wouldn't drive as well as it does? Driving the car back from the shop it again made me think about this point again: the car seems to be running well, sounds amazing and there are no hiccups or stumbles in the RPM range. With apparently 70% leakdown in both 5 and 6, how can that be? I would imagine the engine running much rougher than it is.

Are you able to post all the codes your getting if it's more than just the misfire codes? Headgaskets are a big job as I'm in the middle of it right now. Another engine is literally cheaper than the labor.

Below are the two reports I got on the compression, leakdown, and the misfire codes. Sorry to hear you're in the middle of it, yes they certainly sound like a PITA

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[Arith2]

Thank you for this, I needed to hear that, and it makes sense. The car however is not fixed - I didn't have them do the headgasket as I can't throw $6k at the car right now (that was their quote to me for doing just the top end) - so although it seems like it's driving totally OK, it's still driving on 120psi in both 5 and 6 apparently, and so for the time being I'm parking it and not driving it until I can get it fixed - I don't want to keep driving it and have it get worse if that makes sense

Are you able to post all the codes your getting if it's more than just the misfire codes? Headgaskets are a big job as I'm in the middle of it right now. Another engine is literally cheaper than the labor.

[sapote]

Yeah, take your time and do a careful leak down test, and hopefully no leak. I still don't quite understand that a bad head gasket that only caused misfire at idle but perfectly fine during driving.

[ChapterM3]

45 miles is nothing in my shop, just a fyi. I had a car come in that was misdiagnosed as needing a headgasket (M54) and the client had already approved and engine replacement but I was skeptical of the failure so I probably drove it 40 miles on the diagnosis to find out it had a bad crank case vent valve. After fixing it I put another 45 on it to verify. It then came right back with a bad brake pressure sensor (previously replaced URO brand, not by me) and I put another 40 on it just making sure it was truly good to go. If you trust your shop don't sweat the miles they are sorting your car. If you don't trust them, then maybe they are going to lunch, lol.

Honestly from everything you had stated I would get a second opinion and not tell the 2nd shop anything that the first shop told you. Go in and tell them what you observed like you did the first shop and see what they say. IF the come to the same conclusion you have your answer.

Anri what is your method for test a fan clutch operation?

Thank you for this input, I wonder if it's been misdiagnosed - I'll get a second opinion just as you stated, that's a great piece of advice - thank you!

I would do a leakdown for my own peace of mind.

If it's driving fine then I wouldn't worry and just keep driving it.

Yeah I think I'll either do my own or get another shop to do it

1. Yes, try not to run the engine until it's fixed, as the leaking hot combustion gas can eat through the metal more (head and block if leaking between 5 and 6 thin wall).
2. When the 5 and 6 misfired, this could affected the crank rotational speed and many times caused the incorrect misfire detection on the other normal cylinders.
3. All of the plugs look the same and not too bad. I would have a second shop to check.

1. Understood - think it's fine to go to get a second opinion or rather tow it there?
2. Even if these misfires are happening only at startup? While the car is driving it feels absolutely fine
3. I'll get a second opinion, thank you for this. I have access to a shop that I could do this on my own, I would just need to get a leak-down kit

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Thank you all for chiming in, I really appreciate it and will keep updating this thread as I discover new things about the car, stay tuned

[sapote]

The car however is not fixed - I didn't have them do the headgasket as I can't throw $6k at the car right now (that was their quote to me for doing just the top end) - so although it seems like it's driving totally OK, 1. it's still driving on 120psi in both 5 and 6 apparently, and so for the time being I'm parking it and not driving it until I can get it fixed - I don't want to keep driving it and have it get worse if that makes sense
2. Something just doesn't add up to me of why 3,4, and 5 would be misfiring if the break in the HG is indicated between 5 and 6 - if anyone knows the answer of why this is occurring, that would help settle my mind.

1. Yes, try not to run the engine until it's fixed, as the leaking hot combustion gas can eat through the metal more (head and block if leaking between 5 and 6 thin wall).
2. When the 5 and 6 misfired, this could affected the crank rotational speed and many times caused the incorrect misfire detection on the other normal cylinders.
3. All of the plugs look the same and not too bad. I would have a second shop to check.

[cobra]

I would do a leakdown for my own peace of mind.

If it's driving fine then I wouldn't worry and just keep driving it.