I spent the weekend working on my X5 project and it was definitely 1 step forward, two steps back!

First, the good news. I installed the new tie rods and sway bar links and was able to drive the car for the first time since buying it almost 3 weeks ago. It behaved very well - no vibration or shimmy. Good handling, and good tracking in spite of my quickie DIY alignment. It doesn't pull to either side really drives nicely. The transmission seemed to shift well, too.

But it was a quick drive and I stayed close to home. I never know what to expect the first time I drive a project car and don't want to go any farther than I think my wife will be willing to come get me if needed. It was about a 10 minute drive and as I pulled into my neighborhood, the engine temp started to rise. I was within sight of my house when it nearly reached the red, so I shut it down and coasted to a stop. After about 10 minutes it had cooled down enough to go the last 500 feet to my driveway. Hmmmm, now it's a little clearer why it may have been abandoned!

So now what? I started to look a little closer and found some interesting and, quite frankly, contradictory things. Upon closer inspection, it's obvious the head has been off and refreshed. It's very clean - much cleaner than the rest of the engine. There are also copper colored flakes in the coolant. That tells me that somebody tried to stop a head gasket leak with that stuff you pour into the radiator. But was that before or after the head was redone? There is also some evidence of water in the oil. You would think that whoever had the head off would have changed the oil afterwards, but maybe they didn't? Did these things lead to the head gasket being replaced and the person (or shop) who did the work didn't bother to change the oil and flush the coolant when the job was done? Or, was the job botched and now needs to be redone? Maybe they reused the head bolts, or there are stripped holes in the block so they can't be torqued properly. Who knows!

I decided to do a compression test to see if that would tell me anything. I got the engine up to temperature, but then it took me almost 20 minutes to find the frikkin DME relay. Plus the 15 minutes it took to get the coils and plugs out. So it had some time to cool before I tested. I say this because the numbers are higher than I would have expected. This is what I got when I tested it:

1 - 186
2 - 179
3 - 186
4 - 184
5 - 186
6 - 187

I don't have an E53 Bentley manual, but I do have a set for the E39. And it has info for the M54 engine since it was also available in the E39. According to the manual and TIS, the compression should be 142-156 on a hot engine. So my numbers seems high. But maybe because it had time to cool down? The main thing, though, is how consistent they are. Although #2 does seem a tad low. Which is the opposite of what I would expect from a bad head gasket. So if the head gasket is okay, what's going on?

I have replaced a HG before and am up to job. I just don't want to. The last time I did it, I bought all the special tools for the S52 in my E36 M3. But of course, different special tools are needed for the M54. Does anybody know of a source to borrow or rent the two VANOS alignment tools I'll need if I decide to pull the head to have a look-see?

After thinking about while mowing the grass (I do my best thinking on the lawnmower), this is my next step - unless somebody has a better idea:

Drain the coolant (it's mostly water, anyway), swap out the water pump, thermostat, expansion tank, upper/lower radiator hoses, refill with BMW coolant, go for a drive and see what happens. If it runs hot again, I'll know there's definitely something wrong. Maybe I'll do another compression test once it's fully up to temperate (now that I know where the relay is).

The only thing is that I'm not sure what to do next if it does run hot. By that point I'll have cooling system parts that are known to be good. And the compression test doesn't shout that the head-to-block seal is a problem. So then what?