[technician117]

My original M5 currently has 339,000 miles on it. I'm the 2nd owner, having bought the car when it had 117k miles on it. I have full history on the car. The rod bearings were replaced at 334k miles and didn't look bad at all. I did the timing chains and guides 2-3k miles later because the u guide was failing (broken retaining clips). The two side rails looked completely fine.

Expanding on Sailors comments - high mileage can mean the car saw a lot of highway time, which is generally very easy on the drivetrain. The main thing is the potential for deferred maintenance. That would be my concern before rod bearings or guides came into question. There are many items that should be replaced as PM for correct operation of the engine at it's full potential. Those items add up to a lot of cash in parts, let alone if you have to pay someone to change them too.

 

[technician117]

You nailed it. Compression test and more importantly, leak down test. Note that compression tests are hard to get accurate results on these engines. Must do it hot and must purge the fuel from the injectors at minimum. If the leak test results are bad, then you could scope the afflicted cylinder(s) for bore scoring.

Drop the lower oil pan and pull the oil pump pickup screen. You have to open the "lid". Be very careful not to break the plastic as these are not replaceable IIRC. Look for plastic "tabs" in there. Lastly, the best way to check the guides is to pull the valve covers. You're not going to do this prepurchase though. Once the covers are off, you can inspect the u guide top edge to see how far it's slipping off the rail and/or if the chain is starting to ride up on the rail edge.

Honestly, yes the engine is expensive to repair, but don't overlook other aspects of the car, namely rust like Sailor pointed out. Jack pads rotting out are a death sentence for most e39's as the work to replace them with clean metal is extensive work. If you can't safely jack up or put jackstands on the jack pad locations, it becomes much harder to work on the car, which one with those miles will certainly need.

Good luck and post up when you buy it!

 

[technician117]

Congrats and good luck! Please read up on old threads asking about what preventative maintenance to tackle. If I were you, the first thing you should do is tackle the rust though. If you delay now, you'll keep pushing it off and it might become more hassle than it's worth.

 

[technician117]

Just to note, a brand new guide will allow some movement of the plastic. That's why they fail in the first place IMO. I agree with the others. Not in a state that you shouldn't risk starting the engine, but I wouldn't drive it much!

 

[technician117]

I've heard the Delphi parts are supposed to be pretty good as well.

 

[technician117]

For passing your inspection, I think all you need to do are those VC gaskets. They're notorious for leaking and from the looks of it, yours haven't been changed, maybe ever. lol. I'd clean everything really good, install new VC gaskets and go from there. I'd hold off on the front main seal until you're doing the timing guides. They do leak, but usually not enough to be physically leaking/dripping like VC gaskets do. Another thing that can leak and drip are Vanos solenoid orings. If you pop the square covers off and see oil inside, you know at least one oring is leaking (yes, technically a "D" ring").