DIY: Do It Yourself
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|03-27-2012, 12:21 PM||#1|
Join Date: Sep 2009
My Ride: 330 Ci convertible
Project M54 Engine: Head
Link to other parts of the project
Once the camshafts have been removed, pulling off the head is a pretty simple process. The head can be removed with the camshafts still attached, but unless you weren't planning to remove the camshafts at all, I would remove them first, and then pull off the head. The head with everything off it is not that heavy (21kg). Putting it on and off can easily be done with one person using a little care. If the camshafts are fitted, the extra weight makes it all a bit difficult (33kg).
My Bentley manual calls for a special E12 torx socket BMW tool to remove the head bolts. I don't know why this is. I have a standard Kincrome set of torx sockets. The E12 one with an extension bar worked with no issues getting in there. With the camshafts removed there is loads of room. With the camshafts fitted, it's pretty tight, but these tools still worked.
While there was plenty of torque on the bolts, it was less than I expected. I only had a breaker bar that was about a foot long, and to be honest I was surprised to find that this was enough. Something a bit longer would have made it a breeze. For installation I would use something quite long so it is easy to get the correct angle of rotation after initial torquing.
There are 16 bolts in total. The 14 main M10 bolts, plus another two smaller bolts that go into the timing chain cover at the front. When removing the main M10 bolts, my Bentley manual calls for a progressive loosening of the outside bolts first moving into the center bolts last.
When the head bolts are removed, pulling off the head is quite simple. The head gasket is metal, so nothing is stuck, and everything just pulls apart nicely.
This is what the bottom of the head looks like after removal.
And the top of the block
Installation of the head is something that needs to be done properly, otherwise you will have problems later.
You will need:
- New head bolts
- New head gasket
-Cleaned up the head and block perfectly with no remains of the previous gasket
Please excuse the state of the block and head in these photos, also I'm not using a new gasket or bolts. I just wanted to practice a few times to see how it all went, and take a few photos.
One of the difficulties is placing the head onto the block so it goes straight on, and not damage or scratch anything. I used two 10mm wooden dowels that fit into the bolt holes where the head alignment dowels are fitted. Also the timing chain gets in way. If you have a second person, they can feed it through. If not, it is a simple process of stacking the chain up after you have pulled the chain guides together. Don't worry about the chain falling down. I actually tried to push it down there. It won't fit. Also, there is a lip on the inside of the timing chain cover that sits under the crankshaft sprocket that stops the chain falling off the sprocket. It's designed so that when you remove the upper timing sprockets, there is no way the chain will come off the lower sprocket, and the chain can't fall down the hole. When I removed all of the timing mechanism weeks ago, I always had the chain tied to something to stop it from falling down. I know now that this is not required.
Once the head is on, the bolts need to fitted and tightened. When putting in the bolts, make sure you give the threads and the washer a good squirt of oil so they torque correctly.
The torquing sequence is below. The Bentley manual calls for initially 40Nm. After this, go over each bolt in the sequence and turn 90 degrees. Now repeat the whole sequence again with a further 90 degrees of turn. At the end, each bolt will have 40 Nm + 90 deg + 90 deg.
When I initially put on 40Nm in the sequence, I went back to the center bolts and found they needed a bit of a tweak to get them to 40Nm again. Make sure you go over each bolt in sequence again and ensure they all have 40Nm applied.
To turn each bolt through 90 degrees, this is what I used. I made it up on my computer, then printed and laminated it. You could just as easily hand write this on some cardboard using a protractor. The bottom circular piece that has the angles marked is loose on the extension bar and doesn't turn. The arrow is snugly fit on the bar, and turns as you tighten the bolt. On the head I found it easiest to stick the circular piece to the head with some blu tac. You can do this because the top of the head is flat. On other components that aren't flat, you could use a wire that is bolted to the block, and the other end holds onto the circular piece.
The way to do this is to go give each bolt 90 degrees of turn in the correct sequence, then go back again and repeat. This will require a fair bit of force. I used a breaker bar that was1m long, and found that I only needed to hold it about 60cm along to make an easy job of it.
Doing all of this is quite easy, as long as you take your time and are methodical in the sequence you tighten the bolts. The biggest issue is getting lost in your tightening sequence, and either not torquing one bolt, or doing it twice. When having a bit of a practice, I was very quickly asking myself "which one did I just tighten". My best advice is to place something next to each bolt before you start, and then remove it when you are done with that bolt. The problem is that if you get mixed up you will have to loosen everything off and start from scratch. This means a new gasket, new bolts, and lots of tears. BAD.
Moral of the story. Take your time. Come up with a plan so the sequence of tightening is done correctly.
With the head off, it needs to be tested for flatness. If not flat it will need to be machined flat prior to installation. The maximum it is allowed to be machined is 0.3mm. Then a head gasket that is 0.3mm thicker would be used.
Here is how you test for flatness. The specs from the BMW TIS are a maximum of 0.05mm deviation. In other words, when you put on the straight edge, you shouldn't be able to get a 0.05mm feeler gauge in there anywhere.
The block needs to be tested in the same manner.
Also inside the head is an oil non return valve. There are two oil feed lines that go to the head. One goes to the camshafts, the other goes to the chain tensioners. Only the line that goes to the camshafts has a non return valve.
Last edited by jjrichar; 04-29-2012 at 11:54 AM.
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