Saturday, November 29, 2008

Replacing the Head Gasket Part Two

I missed a couple of steps on Thanksgiving when I started tearing the head down. I forgot to disconnect the exhaust from the head, so I started with that today. It took me a good amount of time to do it since you have to remove 24 nuts that hold the manifold to the head. Most of the nuts came out with the studs, all except for two of them. I also had to remove the six nuts from where the headers connect to the exhaust pipes, it made it much easier to get the headers off.

The rest of the way, I made sure to follow the Bentley's Manual step by step. Everything went pretty well.

One of the things I've done that I've never done before was take great care in documenting and labeling where everything goes. Last time I took the Intake Manifold off of the 93 525i, I mixed up the fuel lines when I put it back together and it wouldn't start. It took me about an hour to figure out what I did. Hopefully the extra time I took to mark everything will relieve me from having to spend time troubleshooting a problem.

There wasn't a whole lot of stuff to take pictures of until I pulled the head off, so I will put a couple of pictures at the end of this post.

Over the summer, I purchased all of the special BMW tools you need to do a head gasket replacement. You really do need them if you want to do the job right without breaking anything. I used the tools at the appropriate times and everything came apart as it should have.

Once I had all of the head bolts out, I was ready to take the head off. I gave it a little tug, nothing. I tapped it a couple of times with a rubber mallet and tried again, it moved. I grabbed it on both ends and the front came up first and then the rear. I didn't have my body positioned like I should have, so I set it down to reposition my feet. I then pulled up and it came out. Once I had it off the block, I balanced the head on the inside of the fender well so I could fish the timing chain through the head to finish getting it out of the engine compartment. I took it over and put it with all the other parts on my work bench. It is heavier than it looks.

Once the head was off, I looked to see where the gasket had failed. I found a spot on the exhaust side right between the #3 and #4 cylinders. I didn't see a break, but you could tell it had been leaking there. Inside of the the exhaust header for the #3 cylinder, you could see that it was sort of greasy looking. The water must have been going through that cylinder. I remember when I was having the problem earlier in the year I pulled the spark plugs and the #3 cylinder plug was discolored, so I'm pretty sure that was where the problem is.

This picture shows the head off of the block.

This is a close up of the area where I believe the leak to be in the head gasket. The spot is directly below the middle cylinder, right in the middle of the picture.

This is just a picture of all the stuff I've taken off the car. I had some old pieces of pressboard left over from some project I did a while back, so I cleared off my work bench and put the pressboard on top of it. As I removed the parts, I put them there and wrote directly on the pressboard where it came from. I think it will work well, there are a lot of small parts, nuts, bolts, you know. I've documented pretty well I think.

One thing did happen that I didn't plan on, probably cost me an extra $150 and several hours of time. When I was trying to pull the head off, I must have caught the primary chain tensioner guide and broke the leading edge off of it. Actually I'm glad I found it. It could have been very easy to not find it and put everything back together. Anyway, to replace the guide, you have to remove the timing chain cover. To remove the cover you have to remove the crankshaft pulley, all of the belts, two belt pulleys, one tensioner and you have to drop the oil pan.

I will tackle the oil pan and then the timing cover on Monday.

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