Dakar Rebuild - part 1

I broke it! :-(

As it stood, I simply didn't have the time to tackle this properly, and so the poor Dakar stood looking miserable in my yard for quite a few months. As the demands on my time decreased a little, I decided to get going again as seeing SDS stood there every time I walked past was getting to me.

I decided to do a quick inspection before I took anything seriously to bits, and so started stripping the engine in situ. A large quantity of wildlife seemed to have moved into the engine bay along with most of the leaves from the tree under which it was parked, so this all had to be dispatched first.

Most of the following photos are clickable - it will open a pop-up with a larger version of the photo.

Plenum chamber off (had to be done first otherwise it's incredibly difficult to get to the bolts that secure the inlet manifold)

Inlet manifold removed. Seems as if something had started making a nest under here...

Seeing as the headers were in such a state, I decided to remove them and clean them up a bit. Coaxing the header bolts out took the best part of a day!

After peeling the valley gasket out, a very healthy looking top-end presented itself:

Encouraged, I pulled the heads off. This is where I started to get a bit disheartened - there were no obvious signs of blow-by, either cylinder-to-cylinder or to the water jacket:

On the plus side, the cylinder condition appeared to be as sweet as a nut, if a bit oily, perhaps:

As I couldn't see anything obviously wrong, I decided to fit a composite gasket. Yes, these lower compression ratios, but I figured it'd ensure a decent seal and prove once and for all if it was the head gasket:

It wasn't. Started it up after putting the top end together and within ten minutes it was boiling over - exactly the same scenario as before.

I flushed and checked the radiator, header tank, water pump etc. and all were in good order and free-flowing, so there was another point where combustion gases were escaping from the cylinder and into the water jacket.

After asking around on various forums, the common concensus was that the 3.9 is particularly prone to cracking of the block behind the cylinder liners. This allows the cylinder contents (usually number 7 cylinder) to escape and hence pressurise the water jacket. One of the symptoms of this, though, is to have the steel liner slip in its bore so it no longer sits flush with the top of the block. There was no evidence of this on my engine, and so it either simply hasn't slipped to an extent that was perceptable OR the heads are cracked.

The heads came off again (I was too annoyed to be taking pictures by this stage!) and I inspected the liner positioning once again, as well as a much more thorough examination of the heads themselves. Both revealed nothing, and so I decided to simply swap the engine out: I could then fiddle with misbehaving item at a later date.