525i Head

I think you found the crack steve. It can't be quite made out well under zoom due to the resulting loss in resolution but you're probably right.

Sir, i don't think cracked heads can be repaired with any security. The aluminium allow combination in the head is usually a trade secret and if you use the wrong filler alloy, it may not work well with the rest of the head under heat. They'll have to take an old cracked head, melt it down, and use that metal as filler.

Either that or they the head needs to be totally recast, which is prohibitively expensive. You only do that if you're dealing with a super vintage engine where spare parts are not available and essentially need to be made from scratch, which fortunately is not the case with our model as yet.

Originally Posted by ricks5series

It's hard to see with this photo but evident with the naked one. I didn't see it at first until the machinist pointed right to it. He also has a BMW, and even has the same head in the shop for a customer. Then his assistant walked out and even before looking at it stated that it must be one of the center cylinders because it's common on these heads. So no, it wasn't pressure tested just visually, it's there believe me.

Well perhaps sometime after all this is over, you could clean up that portion with degreaser and post up a clearer picture.

I had a cracked head once on my e34...and yes i do believe it was on one of the centre cylinders...either no3 or no4......was not on bimmerfest then and did not think to take pictures, wish i did. However, I've never heard that this commonly occurs on our cars. Is there something that can be done to reinforce that area, perhaps......no i doubt anything is possible.

Rick my friend please forget about it, have a shower and a beer, go to bed. Tomorrow is a new day and new opportunities will arise.

i have a head from a 94 325 with 94000 on it i would let go cheap if that would help you. the shipping is still a bitch though. get a shipping quote and let me know.

Originally Posted by BMR_LVR

Is that the crack(s) at the 2 and 3 o'clock positions on the combustion chamber? If not, would you be able to edit the photo with a red circle or arrow pointing to the crack?

Have you decided what you plan to do regarding repair (doubtfull this could be done where the crack is ) vs. replacement?

Steve

PS: This scenario is one of the reasons I did the full coolant system overhaul. I was afraid of a catastrophic failure resulting in a rapid overheat and blown HG or cracked head

PPS: Sorry if you've already explained this (I reviewed your first post), but was this due to an overheat situation? If so, what were the circumstances?

This is a more localized shot of the small crack between the marked parenthesis.

Thanks for the clarification Rick. Man, it's amazing that such a small crack can completely screw up an engine.

Again, was this from an overheat situation?

Steve

Originally Posted by BMR_LVR

Thanks for the clarification Rick. Man, it's amazing that such a small crack can completely screw up an engine.

Again, was this from an overheat situation?

Steve

I don't believe it was Steve,
A week before it did overheat due to the loss of coolant I experienced what now turned out to be hydro-locking when I attempted to start in the mornings. I thought it was rather odd, the engine would turn then abruptly stop then would turn over and start. I could only guess that when the valves opened up the coolant was let out of the cylinder. I also had to put in a lot of coolant the previous week. So it was leaking into the # 3 cylinder weeks in advance.
From what I've researched, aluminum heads simply form minute cracks from the repeated expansion rates due to heating and cooling. Throw in the fact that aluminum expand & contracts at twice the rate than the iron block it sits on.
So no, it wasn't due to an over heating situation.

Originally Posted by ricks5series

I don't believe it was Steve,
A week before it did overheat due to the loss of coolant I experienced what now turned out to be hydro-locking when I attempted to start in the mornings. I thought it was rather odd, the engine would turn then abruptly stop then would turn over and start. I could only guess that when the valves opened up the coolant was let out of the cylinder. I also had to put in a lot of coolant the previous week. So it was leaking into the # 3 cylinder weeks in advance.
From what I've researched, aluminum heads simply form minute cracks from the repeated expansion rates due to heating and cooling. Throw in the fact that aluminum expand & contracts at twice the rate than the iron block it sits on.
So no, it wasn't due to an over heating situation.

Wow. Scary to know it could happen with no overheat. However, I think that what you experienced would be extremely uncommon.

I agree that a lot of fluid in a cylinder will cause the hydrolock. If the fluid happens to get in the cylinder and then the next stroke happens to be the compression stroke, then both valves would be closed and there would be nowhere for the fluid to go. And it obviously cannot compress.

Keep us updated on how things go.

Originally Posted by BMR_LVR

Wow. Scary to know it could happen with no overheat. However, I think that what you experienced would be extremely uncommon.

I agree that a lot of fluid in a cylinder will cause the hydrolock. If the fluid happens to get in the cylinder and then the next stroke happens to be the compression stroke, then both valves would be closed and there would be nowhere for the fluid to go. And it obviously cannot compress.

Keep us updated on how things go.

Will do, located a complete motor but trying to buy just the head. They'll let me know in a few days if they want part with the head since they haven't had luck selling the entire engine. I suspect its because its still in the vehicle.

Originally Posted by ricks5series

Will do, located a complete motor but trying to buy just the head. They'll let me know in a few days if they want part with the head since they haven't had luck selling the entire engine. I suspect its because its still in the vehicle.

Now that you have pulled a head one time, how long do you think it would take you to pull it if the seller agrees to just pull the head?

Originally Posted by BMR_LVR

Now that you have pulled a head one time, how long do you think it would take you to pull it if the seller agrees to just pull the head?

I would guess a couple of hours. Maybe less since nothing has to be labeled. It's in a 3 series so it might be tight towards the firewall. If I had an extra pairs of hands, I'd consider taking the entire engine but its just me. So I'm crossing my fingers that she'll part with the head and call or email me.

Originally Posted by ricks5series

I would guess a couple of hours. Maybe less since nothing has to be labeled. It's in a 3 series so it might be tight towards the firewall. If I had an extra pairs of hands, I'd consider taking the entire engine but its just me. So I'm crossing my fingers that she'll part with the head and call or email me.

I'm sure she will. Most yards will not bother with this and she'll have to sit on it for months if she doesn't do this with you. Do please check the head for cracks and straightness.

Aluminium is considered a soft metal for cylinder head applications, which is why they've alloyed it with something else to make it stronger. And I agree with steve about the cause of the microfissure......i don't think its supposed to occur due to repeated hot/cold cycles. How long have you had this car? Are you still in touch with the po? If you are, perhaps you could call them up and ask them if it ever overheated or if they ever did any work on it...

So after an unsuccessful, relentless attempt of trying to find a used head here on the forum as well as on CL I've decided to place an order (out of state) for a completely rebuilt head. Unfortunately, a few members offered but never replied to my pm's. No hard feelings, life goes on.
After many questions to the machinist I am confident with this purchase knowing its been machined to the highest standards and I'll post of pic of it when it arrives at my doorstep early next week in case anyone is in need of a top notch rebuilt head.

Roberto, you are by far "the" best forumer I've ever met who went above and beyond the call of duty to assist another forum member in trying to find a cylinder head. And trust me, I've met many here and other forums for my other vehicles.

So here's to you mate

i dont know if you mean me but i never received a pm. just check now and nothing. last one from roberto 1/14/11.

Originally Posted by injunmort

i dont know if you mean me but i never received a pm. just check now and nothing. last one from roberto 1/14/11.

Injunmort,
I thought you were one of the ones I sent a pm to but I just checked my log and didn't see you there. I could have swore I sent it, even told Roberto. Perhaps some pm's fall thru the cracks?
So then, no you weren't one of them who didn't respond, lol.
No worries, I'm good with the purchase and just excited about getting this head next week.

alls good, my own opinion as to why the hg fails even without overheating has to do with the vastly different expansion rates of the two metals it is sandwiched it. the aluminum head expands more and faster than the cast iron block and effectively "scubs" the hg. after many, many many heat cycles the gasket simply fails. this is common on brittish parralell twin motorcycles at the base of the cylinder block. the case is alum, the cyl are cast iron and just a flimsy piece of paper between. the rocking forces and different expansion rates of the cyl/case the gasket doesnt stand a chance and they all end up leaking at the cylinder base. fwiw.

Originally Posted by injunmort

alls good, my own opinion as to why the hg fails even without overheating has to do with the vastly different expansion rates of the two metals it is sandwiched it. the aluminum head expands more and faster than the cast iron block and effectively "scubs" the hg. after many, many many heat cycles the gasket simply fails. this is common on brittish parralell twin motorcycles at the base of the cylinder block. the case is alum, the cyl are cast iron and just a flimsy piece of paper between. the rocking forces and different expansion rates of the cyl/case the gasket doesnt stand a chance and they all end up leaking at the cylinder base. fwiw.

Injunmort,
After extensive research on aluminum heads I couldn't agree with you more.
For anyone interested in learning more about aluminum heads here is a great article I found.

http://www.enginebuildermag.com/Arti...k_repairs.aspx

For what its worth, cylinder heads are rarely made of pure aluminium. Its usually an alloy of some kind. Alloys are used because they resist cracking, even after millions of extreme heat cycles. That's the whole point of rnd. Alloys are also used in aircraft engines and airframes for exactly the same reason. You don't hear about engines cracking up in reputed airplanes.

Rick, while the hydrolocking that you experienced clearly did not help things, you've also stated that the cylinder was probably leaking a few weeks before this as you had to top up coolant. You've also reported that your head gasket was normal upon inspection. Thus, the coolant was probably being lost through a crack in the cylinder head.

Why did that happen? How did that occur? I want you to really think hard about this. It could be very important for you to track down. Here's why : it is possible that the problem that ultimately lead to your cracked head is still in your car.

My cylinder head cracked in August 09. 3 weeks before it did, my engine overheated. There was no water in the radiator although the last time i had checkedm maybe a month before that, coolant levels were normal. I was at a workshop by sheer coincidence. The mech flushed the rad and filled it back up. 3 weeks later, the engine overheated again. Same cause. This time i did something really stupid...i poured cold water into the hot engine before waiting for it to cool down first (30 minutes required during daytime summertime, from what i've read). It kept overheating over the next 2 weeks and i kept pouring water in while it was still hot. When i checked the oil, there was no water in there, and there was no steam coming out of the tailpipe.

At some point, the thermal shock of cold water hitting a hot head would have did the trick, and either cracked the head or causes a really tiny crack to become larger (although it was engine). The last time i did this, i noticed alot of steam out the tailpipe, and the oil turned milky. That's when i threw in the towel. I've been bothered by the thought of the underlying cause of the first loss of coolant ever since. I've still not got the answer, although i believe i'm getting closer.

Rick, I just had a thought. Its time for you to do a lifetime radiator modification. Its cheap my friend...under $40 in parts shipped, and that includes a new rad cap and bleed screw. Lets not take the risk buddy...consider it an insurance premium that you're paying on your head repair. If your rad is screwed, your new head will be screwed before too long. I suspect you don't exactly know what caused the initial coolant loss on your car so you can't rule out the radiator.

I just did this mod on my car less than 7 days ago, after thinking about it for nearly 6 months. I've not had time to post the pictures and the writeup over here. I'll work on it within 24 hours. I'll write you offline with more details to sound you out.

When is your new head reaching you? Its best to do what I'll be suggesting before you fix the head up, although of course it is not essential.

Originally Posted by robertobaggio20

For what its worth, cylinder heads are rarely made of pure aluminium. Its usually an alloy of some kind. Alloys are used because they resist cracking, even after millions of extreme heat cycles. That's the whole point of rnd. Alloys are also used in aircraft engines and airframes for exactly the same reason. You don't hear about engines cracking up in reputed airplanes. Valid point, but as injunmort mentioned, the very fact that the head is composed of an aluminum alloy and the block is an iron alloy, rates of expansion and contraction are different. I'm not familiar with aircraft engines and don't know if the heads and engine blocks are different in material.

Rick, while the hydrolocking that you experienced clearly did not help things, you've also stated that the cylinder was probably leaking a few weeks before this as you had to top up coolant. You've also reported that your head gasket was normal upon inspection. Thus, the coolant was probably being lost through a crack in the cylinder head.
It was indeed but I'm pretty certain I've located the slow coolant leak. Upon cleaning the individual parts, I noticed the water outlet from the rear of the head had dried coolant/water deposits encrusted around the nipple and the water hose was sort of expanded. I should have taken a picture before cleaning it all up. I boiled the outlet in vinegar (trick I learned from the motorcycle forum) just to remove all of the hardened deposits. I already have a new coolant hose. A notation to everyone here, take a mirror and bright light source and inspect all of the water connections for small coolant leakage under the intake manifold. Those clamps tend to wiggle themselves loose over time.


Why did that happen? How did that occur? I want you to really think hard about this. It could be very important for you to track down. Here's why : it is possible that the problem that ultimately lead to your cracked head is still in your car. See above

My cylinder head cracked in August 09. 3 weeks before it did, my engine overheated. There was no water in the radiator although the last time i had checkedm maybe a month before that, coolant levels were normal. I was at a workshop by sheer coincidence. The mech flushed the rad and filled it back up. 3 weeks later, the engine overheated again. Same cause. This time i did something really stupid...i poured cold water into the hot engine before waiting for it to cool down first (30 minutes required during daytime summertime, from what i've read). It kept overheating over the next 2 weeks and i kept pouring water in while it was still hot. When i checked the oil, there was no water in there, and there was no steam coming out of the tailpipe.

At some point, the thermal shock of cold water hitting a hot head would have did the trick, and either cracked the head or causes a really tiny crack to become larger (although it was engine). The last time i did this, i noticed alot of steam out the tailpipe, and the oil turned milky. That's when i threw in the towel. I've been bothered by the thought of the underlying cause of the first loss of coolant ever since. I've still not got the answer, although i believe i'm getting closer.

Rick, I just had a thought. Its time for you to do a lifetime radiator modification. Its cheap my friend...under $40 in parts shipped, and that includes a new rad cap and bleed screw. Lets not take the risk buddy...consider it an insurance premium that you're paying on your head repair. If your rad is screwed, your new head will be screwed before too long. I suspect you don't exactly know what caused the initial coolant loss on your car so you can't rule out the radiator.
I've replaced the radiator a couple of years ago and it is in working order, also replaced the upper and lower hoses. I do plan on replacing the cap and bleed valve per your suggestion and as I've mentioned earlier, I already have to newer composite water pump. I replaced the wp with a metal impeller two years ago when I bought the new radiator but upon inspecting the wp pump, noticed the shaft moved a bit. When the car was running I did notice the fan wobbling just a bit (indication either the fan clutch bearing or the water pump bearing are bad) and sure enough, when I pulled the pump out, the shaft was a bit loose. I've read many articles stating that unless the shaft is replaced with a heavier one, a metal impeller (due to its weight) will ruin the bearing in the shaft. That's exactly what I think happened to my pump. It was working but sooner or later the bearings would have failed.

I just did this mod on my car less than 7 days ago, after thinking about it for nearly 6 months. I've not had time to post the pictures and the writeup over here. I'll work on it within 24 hours. I'll write you offline with more details to sound you out. Looking forward to seeing it.

When is your new head reaching you? Its best to do what I'll be suggesting before you fix the head up, although of course it is not essential.

UPS tracking indicates it will arrive this coming Thursday. And yes, I will go over the entire cooling system before the head is installed.

Thought I'd add a couple of pics showing some of the progress.

I've cleaned up the piston tops and block along with many other surrounding parts.

As for the cam removal, I'm following Wayne's procedure he's outlined in his PelicanParts write up. He recommends using a second person to hold the cam so it doesn't rotate in either direction due to the lobes forced onto the valves but I don't have that person. Instead, I've gently clamped the cam with two clamps resting against a part of the head (notice I've wedged a piece of wood and rag for protection) so that the cam does not rotate either way.
Now it's a matter of removing the cap bolts from cylinders 1 thru 5 then removing the cap one from cylinder 6.

You're a smart dude. If i were you, I would send that picture and a writeup on the purpose of the dual cams to pelican parts, and have them update their writeup accordingly. It would benefit tons other people down the line.

Rick, just an idea. This is a good time to consider spray painting parts of your engine. The valve cover and vanos cover are two targets, but another possibility is the oil filter housing and the oil filter housing's head - this would be spray painted silver. It will fade and get dirty over time for sure but until then it would look real purty - which btw is how i would describe your pistons now. Do you have pictures of how they used to look before you cleaned them out ? Could you tell us what you did to execute the repair and how much time was involved?

There is something i wanted to try with regards to cleaning off carbon from the piston tops. And that would be the direct application of a blue flame - kinda like the handheld devices used by solar film/tint applicators who use this to dry the film up from the outside of your windshield. My theory is that the direct blue flame (blue = zero carbon in the flame) would cause the carbon to burn off and turn to ash and carbon dioxide, thus enabling whatever's left to be removed easily. If this worked, then it may be possible to develop a similar blue flame blowtorch with a long thin neck that can be introduced into the combusion chamber via the spark plug socket, to burn off carbon there - all this while the head remains fixed on the engine. An effective in-car combustion chamber decarbonising procedure.

It may be too late to test this on your block, but i'm pretty sure there's some hard carbon on your cylinder head's valve tops. Rick, could you give this method a shot? I'm very curious to see what would happen, and in particular, to see if anything would melt, and if it would, can the exposure period be adjusted to prevent this and yet efficiently burn the carbon off quickly.

Very much obliged for your response, sir. (If there was an icon that represented good natured arm twisting, I would use it here. )


rgds,
Roberto

Originally Posted by robertobaggio20

You're a smart dude. If i were you, I would send that picture and a writeup on the purpose of the dual cams to pelican parts, and have them update their writeup accordingly. It would benefit tons other people down the line.
I just may, also Wayne describes cylinder #6 as #1. It's the other way around as cylinder #1 is always referred to the cylinder at the front of the engine block. I'll wait until this project is completed before I submit anything.

Rick, just an idea. This is a good time to consider spray painting parts of your engine. The valve cover and vanos cover are two targets, but another possibility is the oil filter housing and the oil filter housing's head - this would be spray painted silver. It will fade and get dirty over time for sure but until then it would look real purty - which btw is how i would describe your pistons now. Do you have pictures of how they used to look before you cleaned them out ? Could you tell us what you did to execute the repair and how much time was involved?
Did some research on painting aluminum and unless it's exceptionally clean the paint will eventually peel off and look worse. I called my local machine shop and will have the valve cover tank cleaned but don't know if paint will stick. Depending on what it looks like after cleaning I just may leave it as is.
Yes it comes painted from the factory but of course they not only have a clean environment and the ovens to cure the paint.
Funny you should ask about what the top of the pistons looked like before because my wife asked the same. Would you believe I forgot to take those pics. In any case, they were pretty black and carbonized. I sprayed diesel fuel on them, let them soak and took a Scotch 3M pad to them, wiped them and repeated until they appeared as you see them. The pads are the kinds used for Teflon so they wouldn't damage the aluminum pistons. For the last part of this process I lightly soaked the tops again and blew compressed air in and around the ring area in order to flush out what ever carbon seeped in there.

There is something i wanted to try with regards to cleaning off carbon from the piston tops. And that would be the direct application of a blue flame - kinda like the handheld devices used by solar film/tint applicators who use this to dry the film up from the outside of your windshield. My theory is that the direct blue flame (blue = zero carbon in the flame) would cause the carbon to burn off and turn to ash and carbon dioxide, thus enabling whatever's left to be removed easily. If this worked, then it may be possible to develop a similar blue flame blowtorch with a long thin neck that can be introduced into the combusion chamber via the spark plug socket, to burn off carbon there - all this while the head remains fixed on the engine. An effective in-car combustion chamber decarbonising procedure.

It may be too late to test this on your block, but i'm pretty sure there's some hard carbon on your cylinder head's valve tops. Rick, could you give this method a shot? I'm very curious to see what would happen, and in particular, to see if anything would melt, and if it would, can the exposure period be adjusted to prevent this and yet efficiently burn the carbon off quickly. Very much obliged for your response, sir.
I wouldn't recommend this process (too risky) as it is not needed. The tops of the pistons just need to be as clean as I have them. Now if they were polished? Well, now we enter high performance stuff.


rgds,
Roberto

See my responses in bold.

Could you try the flame procedure it on the valve tops on your old cylinder head? There's no risk there as you're getting rid of it. I don't think the aluminium will melt or anything like that at all...the alloy aluminium has a much higher melting point than pure aluminium.

Another reason why i think this would not damage anything....the combustion chamber is already exposed to fire and brimstone at extremely high pressures - an environment that's much worse than a direct blue flame from a handheld device. In any case, this would be an experiment to try on your old head's valve tops, not on the block.

btw how much scouring did you need to clean off those tops? How long did the whole thing take you for all six chambers?

Originally Posted by robertobaggio20

Could you try the flame procedure it on the valve tops on your old cylinder head? There's no risk there as you're getting rid of it. I don't think the aluminium will melt or anything like that at all...the alloy aluminium has a much higher melting point than pure aluminium.

Another reason why i think this would not damage anything....the combustion chamber is already exposed to fire and brimstone at extremely high pressures - an environment that's much worse than a direct blue flame from a handheld device. In any case, this would be an experiment to try on your old head's valve tops, not on the block.
If time alloys I may try it. My tank is empty. As for doing this to the block itself, its just not a good idea to have a flame in and around the engine compartment but then again that's me.

btw how much scouring did you need to clean off those tops? How long did the whole thing take you for all six chambers?

Really not much scouring but I think it took about 45 minutes or a little more. I tend to take my time and go slowly when doing these things, sort of get into a zen moment. lol It's really not difficult at all and just takes patience.

Yes! The cams have been removed successfully without breaking them. I did ask my pretty assistant (wife) to hold the first cam as a safety precaution just to make certain nothing moved. As I predicted the cams stayed and did not rotate either way but just slowly moved up as I loosened the two remaining nuts 1/8 turn until there wasn't anymore tension. Then I simply unscrewed the rest by hand.

I did notice a couple of the cam caps with very, very minor scorns and will research to see if I could get away with just leaving them as is.

Originally Posted by ricks5series

Really not much scouring but I think it took about 45 minutes or a little more. I tend to take my time and go slowly when doing these things, sort of get into a zen moment. lol It's really not difficult at all and just takes patience.

Yes my friend. You got it right there. Be zen about it. It will then come out perfectly.

Be zen about as many things in life as possible. A great reminder to me at this very moment. Just typing about it here is shifting me into a zen state. Thanks Rick.