[cmdavis3rd]

Greetings all,

I've got an 06 330i sedan with just over 190k on the clock. I am trying to determine if a broken aluminum "head" bolt can cause a coolant leak into the cylinders. Every post I can find related to broken aluminum head bolts all report oil leaks.

Last Saturday I went to start the car from cold and it misfired bad enough to throw the service engine light. I pulled codes and it indicated cylinder 1, 2, and 3 misfires. I pulled the plugs and found coolant in cylinder 1.

From what I understand, head gasket issues with the N52 is virtually unheard of. In fact, I took the car to a shop about a year ago to try and track down coolant loss with no external signs. The shop said that in the 15 years they've been in business, they can count on one hand the number of head gasket issues for the N52. They were able to find a number of small leaks which I've since repaired.

I do not recall every seeing anything that would indicate that the engine had overheated, but with no water temp gauge, I am relying on the dash warning light. Water pump/thermostat was replaced around 106K before it failed.

I'm trying to gauge if it's worth pulling the valve cover and seeing if any are broken. It looks to be about $125 for new bolts, gaskets, etc.

Thanks for the help

[bluewater328]

So, hows your OFHG?

[cmdavis3rd]

That was repaired about 2 years ago along side the oil pan gasket. No new visible oil leaks and I seem to be going through the same amount of oil per oil change as I had after those were fixed.

[hassmaschine]

the "head" bolts that break don't seal any coolant passages - those bolts are steel. the aluminum bolts on the front only really seal the timing case.

It's possible you have a cracked head and it's leaking into the cylinder, but I have never heard of that either on an N52. Even if the pump died it's unlikely it would have caused any damage, and you would have known by the warning lights well before that point.

Is the head off the engine? I'd have it pressure tested if you get to that point.

[E92William]

No brown milky goo inside the engine when you open the oil cap at all? First thing I would do is the chemical test that tests for exhaust gases in the cooling system, pretty safe way to know. What I tried myself in my older cars is to see if there's bubbles in the cooling system running the engine with the coolant cap open, preferably cold. You can also pressure test the cooling system to see if it holds pressure. I suppose you could get away with a compression test too though sometimes this results good and the gasket is blown.

I've yet to see an N52 with a blown Headgasket and the dash warning I believe let's you know when it's just beginning to get warm and it can't bring it down so there's no fear it wouldn't have let you know if it was overheating.

[HydroxFrost]

I'd feel for any oil under the OFHG to see if it might need to be replaced again for some reason, cracked head would be my second guess but its unlikely. I've literally never seen an n52 with a blown head gasket in my life.

[cmdavis3rd]

Thanks for the things to check.

Here is an image of cylinder 1. There isn't a lot of coolant, but I wouldn't know how much would be a lot. As far as I know, any is too much. The coolant is green most likely to me not completely flushing the UV dye from the system after I changed the radiator.


1) hassmaschine Thanks for the clarification on the bolts. The head is still on the engine, I haven't done anything other than pull plugs and do a limited visual inspection.

2) E92William Opening the filler cap, things look as I would expect it to.



Here are some images from my endoscope





How long should the expansion tank stay pressurized after driving? I haven't driven the car since Saturday and I opened the expansion tank cap and a whoosh of air came out.


3) HydroxFrost I just looked all around the OFHG and it all looks dry or from being a 13 year old car.



Thanks again

[hassmaschine]

That looks stuffed, unfortunately. I think you need to pull the head and go from there, I just don't see how that much coolant could get in there without a cracked head or damaged HG. Even if the OFHG was leaking, it would leak it into the oil passages/sump, not into one cylinder. That's like a cup of fluid which is way more than residual.

Maybe it's not even worth pulling the head - I mean, you can get complete N52s for like $900 at a wrecker (maybe even less, but I've seen them for that price recently). Balance that with costs for diagnostics and repair on what is almost certainly a damaged engine. but maybe you'll get lucky and your mechanic can just pressure test the head and replace the gasket if there's not another obvious source of water.

[cmdavis3rd]

Thanks. Obviously I was hoping for a different answer, but knew it was a long shot. I wonder if I could spin this in some manner, its so rare its got to be valuable, right?

A friend of mine suggested the new engine route. My daughter is a few years away from driving, might just park it and save a little each month and use this an an intro to cars. Heck, if she can swap an engine, flat tires should be no problem.

[E92William]

My civic before it blew the Headgasket was like that. Sometimes rarely after sitting for a long time you'd start it up and a cloud of smoke would come out then the next day it'd drive fine and not overheat until well it did finish eating through the gasket. I assume as the engine fully cools down over a few days the parts contract enough for it to let water in but if you drive it regularly it's still tight and warm enough to keep the cylinder sealed, just an speculation of what's maybe going on. There's no way that amount of coolant is normal. I'd start looking for a replacement 30i engine, they're cheap so why not invest that in the car. If it served you that many miles up until now.

At 100 or so an hour in diagnostics you'll spend the cost of the engine like hass said just with a shop doing pressure testing and all that kind of stuff, you could try a mechanic in a bottle fix but I'd also try to get the engine out healthy so you can recoup some of the cost by selling it to someone.

[Brian_TII]

Curious on the new engine route will a newer 2010 / 11 328i engine fit ok? If I was going to replace it, I’d be tempted by the newer head design which I think also has the cam ledges improved too.

Since they are all 3 liters, seems like you could take the 330i intake manifold, oil pan, and valve cover and get the best of all worlds. (Improved head design to prevent “the tick” and improved cam ledge seals, no gouging)

[E92William]

That'd be the best bet though don't the newer engines have issues with the vanos bolts. I think you'd wanna land in a late 08 or early 09 engine to get the updated lifters and no vanos bolts issues

[cmdavis3rd]

While we are going down the frankengine route, would an engine from an AWD model matter if mine is RWD?

[E92William]

The xdrive subframe is very much different aswell as the oil pan. Just get a rwd engine. The xdrive pan is like a big long brick with a hole to mount the axles and front diff while the rwd is like a bucket at the end of an otherwise flat pan. To make it work you'd have to swap them and who knows if the oil pickup setups are different.

[hassmaschine]

Originally Posted by cmdavis3rd

While we are going down the frankengine route, would an engine from an AWD model matter if mine is RWD?

No. Everything is easily swapped over. And if you have the whole engine out, you'd have to be mad to (not) replace the oil pan gasket. There's nothing significantly different about the AWD engine, you'd just put the oil pan on from your old one.

[E92William]

Is the oil pickup not different? I recall seeing a thread about a guy doing it on an N54 and he had some issues with that.

[hassmaschine]

Maybe but it's literally 2 bolts.

[335xi_full_throttle]

At least for the N54 the pickup tubes are different. I swapped a N54 out of a 535xi into a 135i.

[HydroxFrost]

Just try to find the best deal you can on an engine that works, just because the head is warped or the gasket is blown doesn't mean you can't re-use other old parts from your engine like an oil pan, pick up tube, or any new/known working parts you want to use. But if you can save money by going with an awd engine do it.

[smass]

Since you just got that car, don't waste any time with that engine. Someone has been there before you and figuring out what they did will be a waste of time.

Check the link below. They have a 2006 330i w/ just over 100k miles. Complete engine will be $500 with a warranty.

https://www.lkqpickyourpart.com/loca...e-229/recents/

[Brian_TII]

Originally Posted by smass

Since you just got that car, don't waste any time with that engine. Someone has been there before you and figuring out what they did will be a waste of time.

He’s had the car for a long time, like > 10 years. It’s been well maintained. I liked his so much I bought one (almost) just like it 10 years ago. We both still have them, he just drives a lot more than me and unfortunately won the “wow that never happens to N52s game” :-(