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

[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.

[heinzboehmer]

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

[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!

[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?

[Slideways]

Their leak down tester might be off by 30-35% . 120/170 is .70 x 100 is 70%, so those two rear cylinders are down 30% compared to the others.

[ChapterM3]

Their leak down tester might be off by 30-35% . 120/170 is .70 x 100 is 70%, so those two rear cylinders are down 30% compared to the others.

Could this have been from a bad tester or from not achieving TDC on the intake stroke? Thank you for your reply!

[discoelk]

A compression tester is like $30 at harbor freight and it's pretty easy test to do, even for a novice mechanic. You only need basic hand tools and you could verify some of the shops data fairly quickly. If you were local, I'd help you out. It's literally 20mins of work from start to finish.

Make sure you pull all the plugs before doing the test so you get true compress and not a false higher reading on 5&6.

[ChapterM3]

A compression tester is like $30 at harbor freight and it's pretty easy test to do, even for a novice mechanic. You only need basic hand tools and you could verify some of the shops data fairly quickly. If you were local, I'd help you out. It's literally 20mins of work from start to finish.

Make sure you pull all the plugs before doing the test so you get true compress and not a false higher reading on 5&6.

Totally agree - I just bought a compression tester and decided to go this route to 100% make sure before opening the motor - thanks for your comment

[Halftim3]

I believe you need a 12mm adapter, someone correct me if I'm wrong. Also check that the o-rings are in good shape so you get a good seal, should be since your compression tester kit is new, And try to clean the spark plug threads. Good luck 👍

[ChapterM3]

I believe you need a 12mm adapter, someone correct me if I'm wrong. Also check that the o-rings are in good shape so you get a good seal, should be since your compression tester kit is new, And try to clean the spark plug threads. Good luck 👍

Thank you Mike! I got this kit, I think I'll be good or will I need that adapter?

https://www.amazon.com/gp/product/B004K2FSXI/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

[Arith2]

You should have a 5-10% leakdown percentage. I now don't trust a place that calls 35% good. With how well the engine runs, I wouldn't expect even 35% on the bad cylinders. It may be more expensive but my shop has had decent luck with Cornwell tools. It'll run you $200 to $250 total for a leakdown and compression tester but it's worth having quality tools for this. You can buy straight from their website. This is not something I'd cheap out on because it needs to be accurate.

My head got removed because I wanted to install cams. I found the intake valve seats were all about 1.5mm and intake valves on 4 were very collapsed at almost 2mm with some abnormal wear. The Spec is 1.25mm however I doubt there was an actual issue with sealing just yet. I did a whole head refresh which ran about $4k in labor and parts. I just wanted to put my cams in... but I have to be thorough. I do try to follow my slogan. All sensors(cam, crank, knock, throttle position, temp and preasure) are getting replaced along with vacuum hoses, ICV rubber bits, and any soft item I can manage to get my hands on to replace.

For what it's worth, just about anything can be fixed or replaced. It's just $$$ sometimes

[WestBankM4]

I had a HG replacement at 90k miles on my 2003. It cracked between 2 and 3, no misfires, no codes and drove well. It's not until AFTER I did my own HG that I felt the difference. Car was definitely under power.

I drove on my blown HG initially because I couldn't figure out the issue, but I heard sounds in 2nd/3rd/4th @ 2-4k RPM, noticeable only under load, sounded like a bag of marbles. Worse when going up and down the hills of SF. The arching ate a bit of my aluminum head but not substantial enough, the skim cleaned everything right up. I then used a piece of glass with some grit on the bottom block to ensure things are clean and smooth. Vacuum'd up all the debris on the piston's after cleaning them as well.

Long story short, like heinzboehmer said, if you're ever in NorCal there's a group of us that can help get it done in one weekend, this is assuming the machine shop needed to skim your head completes it quickly. My shop took one day to skim and hot tank everything. It's doable and this community can/will help. If there's no space, you can use my 1-car garage to work on it.

Once you're done, you'll realize the actual amount of power you're down even though things "feel" normal. My car was chirping in 1st to 2nd gear after that job, before the job, no dice.

[bmwfnatic]

I want to add to this that while as others have pointed out you should get a proper leak down test done, don’t get your hopes up that your head gasket might actually be fine, it wont be.

My friends car had a blown head gasket too, it drove totally fine, felt fine, didn’t really make any weird noises either, it even went on the dyno, which was the only reason we knew it was down on power. After fitting a new HG and doing a head overhaul it went on the dyno again and made 20hp more.

[ChapterM3]

You should have a 5-10% leakdown percentage. I now don't trust a place that calls 35% good. With how well the engine runs, I wouldn't expect even 35% on the bad cylinders. It may be more expensive but my shop has had decent luck with Cornwell tools. It'll run you $200 to $250 total for a leakdown and compression tester but it's worth having quality tools for this. You can buy straight from their website. This is not something I'd cheap out on because it needs to be accurate.

My head got removed because I wanted to install cams. I found the intake valve seats were all about 1.5mm and intake valves on 4 were very collapsed at almost 2mm with some abnormal wear. The Spec is 1.25mm however I doubt there was an actual issue with sealing just yet. I did a whole head refresh which ran about $4k in labor and parts. I just wanted to put my cams in... but I have to be thorough. I do try to follow my slogan. All sensors(cam, crank, knock, throttle position, temp and preasure) are getting replaced along with vacuum hoses, ICV rubber bits, and any soft item I can manage to get my hands on to replace.

For what it's worth, just about anything can be fixed or replaced. It's just $$$ sometimes

Totally hear you with this - I want to be thorough as well and do it right once. Lot's to consider. This weekend I'll be able to do the compression test again on my own, and will report back after that. I agree with you that 35% leakdown is crazy to call good, and again have verified that really it should only be 5% at maximum. I'm curious what compression numbers I'll get back when I do it.

I had a HG replacement at 90k miles on my 2003. It cracked between 2 and 3, no misfires, no codes and drove well. It's not until AFTER I did my own HG that I felt the difference. Car was definitely under power.

I drove on my blown HG initially because I couldn't figure out the issue, but I heard sounds in 2nd/3rd/4th @ 2-4k RPM, noticeable only under load, sounded like a bag of marbles. Worse when going up and down the hills of SF. The arching ate a bit of my aluminum head but not substantial enough, the skim cleaned everything right up. I then used a piece of glass with some grit on the bottom block to ensure things are clean and smooth. Vacuum'd up all the debris on the piston's after cleaning them as well.

Long story short, like heinzboehmer said, if you're ever in NorCal there's a group of us that can help get it done in one weekend, this is assuming the machine shop needed to skim your head completes it quickly. My shop took one day to skim and hot tank everything. It's doable and this community can/will help. If there's no space, you can use my 1-car garage to work on it.

Once you're done, you'll realize the actual amount of power you're down even though things "feel" normal. My car was chirping in 1st to 2nd gear after that job, before the job, no dice.

Mmmmmmmmm this resonated with me a lot. The slow breakdown of the HG and performance makes sense, I've PM'd you and heinzboehmer to discuss further. I really appreciate the follow up to this and insight!

I want to add to this that while as others have pointed out you should get a proper leak down test done, don’t get your hopes up that your head gasket might actually be fine, it wont be.

My friends car had a blown head gasket too, it drove totally fine, felt fine, didn’t really make any weird noises either, it even went on the dyno, which was the only reason we knew it was down on power. After fitting a new HG and doing a head overhaul it went on the dyno again and made 20hp more.

Thanks for the input, definitely going to be moving forward with a further compression test to decide on next steps

[ChapterM3]

October 19, 2023 - UPDATE 3 - THE M3 IS GETTING THE Anri BUILD TREATMENT

Just marking this section in the thread as the beginning of the build. The car will be pick

The car is going to be picked up to start the build this upcoming week of 10.23 - I'll be adding photos and updates all along the way

Stay tuned!