While trawling through the e60 forums one of the things that I have noticed is that 550i owners tend to complain about a lot fewer issues as compared to the 545i owners. When I say issues, for the sake of this discussion we can limit the conversation to repairs related to the engine. Just wanted to see if there is any substance to say that the 4.8L v8 on the 550i is better in terms of reliability than the 4.4L v8 on the 545i. I can begin with a laundry list of issues that typically characterize the 545i

1. Valve cover gaskets
2. Upper timing cover gaskets
3. Alternator bracket gasket
4. Transmission mechatronics sleeve
5. Vacuum pump and oil switch

I thought it would be interesting to to see if 550i owners had related observations/experiences to share.

 

There's a nice big oil cooler on the 550 that you and I don't have. Rumor has it that it helps with seal life, along with some design fixes. And it plugs in the hole under the alternator bracket, where we have that gasket that's so much trouble.

There a thread somewhere about adding the oil cooler to the 545 as a retrofit.

 

I would definitely agree with your premise that the 4.8L engine is more reliable than 4.4L, especially in the area of engine gasket design.

Unfortunately there are about 15 more "common" 545i failure points to add to your list of 5. Some items on the list are also experienced by 550s although seemingly at a reduced rate. Last time I counted my 545i had experienced 17 out of 20, though thankfully most were with the previous owner who had a bumper to bumper extended warranty, so everything that needed to be fixed was immediately addressed by a dealer (including the dreaded water pipe, alternator bracket gasket and mechatronics sealing sleeve).

You have to be a little careful in drawing final conclusions when comparing the two models as all of the 545i are seven or eight years old, whereas the 550i will range between two and six years old, and age/mileage does matter to some extent.

 

My understanding it's completely different block and has better cooling design due the wider channels or better design to carry heat out. Also weight/power ratio is better so engine tendency working less harder than 4.4L and of course oil cooler, that makes oil last longer so less problem with gasket failures. But I will replace oil 5-7 thousand miles anyway. I don?t want take a risk safe 100 bucks a year then pay 1000 for repair or 3,000-4,000 for valve seals.

 

Can you list out the missing failure points (cringing) so that I know whats to come?

 

Regarding the dreaded water pipe ... is there some improvement in the 550i engine design to mitigate this failure?

 

Transmission mechatronics sleeve as well as problems with mechatronic itself is definitely there - I am getting my 550i back today after a week in service regarding transmission leaks and surges.
Seems like steering leak through active sway bar is also common and quite $$$.

 

545i problems in no particular order (in addition to what you have mentioned);

Lower timing case gasket
Valley pan gasket
Water Pipe
Micro Power Module Melt Down in Trunk
Alternator - Bearings and voltage regulator
Broken wires in trunk lid wiring harness from fatigue (repetitive opening & closing)
Auto Trans Mechatronics failure
Active steering - optical steering angle sensor
Suspension thrust bearing excessive wear
Coolant components leak (Brittle from heat & age) ? y-pipe, vent pipe, lower radiator hose temperature sensor O-ring
Thermostat heater circuit failure
Radiator Failure
Expansion tank leaks
Passenger seat air bag sensor
Water pump leak
Hunting Idle
Weather stripping around front and rear windshield, doors and windows
Drains from sunroof and windshield clog and flood interior of car or e-box
Rear Tires wear out in average 8-15K miles with sport suspension
Factory brake pads blacken wheels in two blocks
ARS hydraulic sway bar leaks

 

Interesting list. Let me be the first to point out that many issues you've noted have nothing in particular to do with the 545 versus any other E60, and a few aren't reliability issues at all. I can report no overly surprising issues on my car, no significant engine-related issues, and only a few items on that list, and only those I would categorize as wear items. I have only 65k miles, so who knows what else is to come. I have no doubt that as the car went through its production cycle it got more reliable generally (I'm sure a 2010 is more generally reliable than my 2005), but on any of these cars out of warranty you're rolling the dice.

 

I agree with jim545. A lot of the issues mentioned above are not 545i specific.

Alternator/water-pump/thermostat/expansion-tank/coolant-pipe-leaks/radiator
>> All german cars (Mercedes/Porsche/BMW) have these issues to some degree. Heck even Land Rovers have these issues.

Rear Tires wear out in average 8-15K miles with sport suspension
>> This is due to the -ive camber on the rears. 0 the camber if you want to avoid premature tire wear.

Weather stripping around front and rear windshield, doors and windows
Drains from sunroof and windshield clog and flood interior of car or e-box
>> unsure as to what degree of exposure to the elements would cause the failures you mention above.