Removing M42 head - problems?

[kmack]

Anybody have problems removing an M42 head?

This evening, I pulled the first headbolt out fine.  The second was a little tough.  The it snapped!  :mad: :eek: :mad:

I'm afraid to pull any more of them out for fear I'll be drilling and tapping every one of them.  Is this a common problem or am I just having bad luck?

[Shocker]

I’ve never seen a BMW head bolt snap before while taking them out but…  I've heard of them braking while on the car (the older 750's were famous for that).   My dad bought a 1989 750il with 80k miles for $1000 with 6 broke head bolts.

[bmwman91]

Well, it depends on where it snapped.  At this point, you HAVE to reove all of them to find out.  You might have lucked out and it left some sticking up so you could get some oil and vice grips on it.  I do not really have any big suggestions to ensure the otherd so not break.  Penetrating oil is not really of much use on those, not do you want it down in the holes.  Good luck.

[kowalski]

previous mechanic was probably a dumbass and didn't put anti seize on the threads causing them to seize together. good luck removing the rest of them...

[2002maniac]

previous mechanic was probably a dumbass and didn't put anti seize on the threads causing them to seize together. good luck removing the rest of them...

I've never put anti-seize on head bolts.

[Alpine003]

I've seen headbolts snap before. Did you loosen all of them in the proper loosening sequence? This is one of the main reasons why this happens.

Another technique is to make sure you apply a quick blow of torque when you first start loosening the bolts. The slower you turn a stuck bolt, the better chance it can fatique and eventually break.

[kmack]

The piece of head bolt that came out is about 3" long.  From a mechanic I talked to today, I may be alright and still have some sticking out of the block.  We'll see.

I knew about the proper tightening sequence, but I've never heard of a proper loosening sequence before, even with other aluminum heads (I've done a few Nissan straight 6 head swaps before).

The first bolt loosened up like all other typical head bolts I've run across.  The second one wouldn't budge.  I used an impact driver on it a few times, then put the breaker bar on it and it just slowly twisted off.

It also was rather cold (for Texas).  It was about 53* outside.  Do you think I might have abetter chance with the remaining bolts if I warm up the head some?  Not with a torch or anything like that, but maybe using an electric blanket or such?  Or just wait for a warmer day....

[Alpine003]

The piece of head bolt that came out is about 3" long.  From a mechanic I talked to today, I may be alright and still have some sticking out of the block.  We'll see.

I knew about the proper tightening sequence, but I've never heard of a proper loosening sequence before, even with other aluminum heads (I've done a few Nissan straight 6 head swaps before).

The first bolt loosened up like all other typical head bolts I've run across.  The second one wouldn't budge.  I used an impact driver on it a few times, then put the breaker bar on it and it just slowly twisted off.

It also was rather cold (for Texas).  It was about 53* outside.  Do you think I might have abetter chance with the remaining bolts if I warm up the head some?  Not with a torch or anything like that, but maybe using an electric blanket or such?  Or just wait for a warmer day....

BWM manual does state a loosening sequence as well. As for headwork, I generally don't like using impact or breaker bar for that very reason. I've taken off heads in 20 degree weather without any issues so I don't think temperature would affect the outcome too much.

[D. Clay]

It also was rather cold (for Texas).  It was about 53* outside.  Do you think I might have abetter chance with the remaining bolts if I warm up the head some?  Not with a torch or anything like that, but maybe using an electric blanket or such?  Or just wait for a warmer day....

In Austin it's been too cold (55 degrees) to work on a car. LOL - We're such lightweights.  Up north they'd be out in that heat wave. Aluminum expands more than steel with heat so it's better to remove the head when the engine is cold. The problem is the threads of the bolts corroding in the block and rarely, the underside of the bolt head to the cylinder head. The threads of head bolts are usually  lightly oiled for accurate torque readings with anti-sieze to the underside of the bolt head (steel and aluminum together).
I know a guy that puts a piece of .75" steel rod on the bolt head and hits it sharply with a hammer. He says it "wakes them up". I don't think this is a scientifically valid method and I've never seen it recommended. It may fracture some of the corrosion but if you knew the guy you might have doubts.  He is incapable of working on a car without great quantities of profanity; usually characterizing the car as a feminine entity with questionable heritage, hygiene, and character.

[kmack]

I did not see any signs of corrosion on the portion of the bolt that broke off nor on the one bolt that came fully out.  Good sign I guess.  I will give the rest of the bolts a sharp tap before trying to work them loose.  I know this works (or helps) with rusted bolts to break the rust free.  I think I also might try to a tighten them slightly before trying to back them out.  

Short of those options, my only available process left will be to get the rest of them out while trying to break as few as possible.  Hopefully, anymore that break, will do so above the cylinder deck.

[Alpine003]

Short of those options, my only available process left will be to get the rest of them out while trying to break as few as possible.  Hopefully, anymore that break, will do so above the cylinder deck.

One option would be to follow the proper BMW loosening sequence which would reduce your chances of breaking bolts. Just download the online M42 manual off this site for the info.

[RED IS 91]

here ya go .............
do ya need the installation sequence also ?

[kmack]

I have the downloadable manual from here.  But it only states an bolt order sequence, not a loosening sequence.
Page 113-6, item 32: "Using Torx E12 socket, remove cylinder head bolts in the sequence indicated.  See Fig 15.  Remove cylinder head and head gasket.  Discard head bolts."

The figure only shows what order in which to remove the bolts.  Starting from the right-most rear corner of the engine.  It mentions nothing about turning each one 90* in the order shown, then another 90* in the order shown, and then pulling them all the way out.  That's why I didn't do it that way.  Between 3 motorcycle rebuilds, and 4 engine swaps in two cars, I've never removed a head bolt in that type of way.

Personally, I think stretch bolts were a poor design for BMW to use, but that's based on personal experience with hard bolts.

Anyway, I'll be pulling (or breaking) the rest of the bolts off by this weekend.  We'll see what the final score is in the end.

[RED IS 91]

You only do the 90 degree thing when your re installing the head .When removing you don't want to stress one area by loosening a certain section ,that's why the sequence.
More scans for ya

[shutter]

+1

Definitely follow the sequences shown above ^^  The full pdf that RedIS posted is on page 2 of the Reference section.  Somehow I missed it at work yesterday and didn't think it made it over with the server change a bit back.  This forum rocks!  Found it today to reference at work  Maybe it should be stickied??

Good luck with the rest.  Out of curiousity, which one snapped?

edit:  oops, sounds like you've got the manual already.