I guess the previous owner wasn't lying...

[tomrdy]

A bit of context... When I bought the car, the previous owner had told me he swapped the engine for one with about 60,XXX kms due to an issue with the original motor. At the time the chassis had 122,XXX kms. He had no receipts to back this up so I've never given it much thought.

When reading about the oil pump nut/harmonic dampener issue, it was found that M54b30 motors after 2002 were updated with a slightly different dampener that had 4PK for the AC belt instead of the previous 5PK.

So, I was having a poke around the motor while the undertray was off and discovered that the AC belt on my engine is 5PK, and not 4PK, practically confirming that this motor is not original to the car as no Z4 would have the 5PK set up - assuming RealOEM is acting as a source of truth.

I'm not sure how I feel about this.

On one hand, assuming that the KMs claimed are true, this motor has lower mileage than the chassis which I think is good - everything on it would be that little bit less worn. On the other hand, the dampener is of the old design - though the differences visually seem imperceptible bar the rib count - and has been associated inconclusively at length as a possible culprit for the oil pump issue.



I'm glad I noticed this though before doing a belt job and getting one for an '04 Z4 that wouldn't fit!

What are member's thoughts? Is this a good or bad thing?

 

[Hairyarse]

I wouldn't have an issue with this. You've bought into the idea with the seller being upfront and you've got a lower mileage engine. As long as you know which parts to buy going forwards for it, then I'd say all is well

 

[bigwinn]

Yeah agree- one of my E30's had 244k on the clock but I knew the engine was only 100k- so as long as I kept on top of preventative maintenance with those two ages/conditions in mind all was well

The previous seller was upfront- I think its a plus point for when you come to sell too as a lower KM engine has to be a plus to anyone who cares about that stuff

 

[tomrdy]

Thanks for the extra perspective guys

I did think perhaps it could be a selling point later - but I have no papers to back it up so it may just scare a buyer away if anything? Selling isn't on the cards anyway though a 3.0 manual (infact any e85/e86 non-M manuals) seem to be rare down here lately for some reason...

 

[tomrdy]

As long as you know which parts to buy going forwards for it, then I'd say all is well

Well in a hilarious turn of events, I was planning to order new belts (just did an oil service and figured its probably time). Promptly added an AC belt for the E46 pre-2002/09 with the 5 rib but thought... I best double check my assumptions outlined in this thread. Don't want to look like an idiot right?

Took a look at the photo again and realised that the pulley on the AC doesn't seem to have 5 ridges - only 4... yet the belt certainly appears to have 5 ribs. Could be lighting at play here? Last time I only reached a hand in while refitting my broken bumper/tray sides to snap a pic.

Screw it. This time I want to grab this belt in my hand to be sure. Lifted the car, took the splash shield off and low-behold... 4 rib AC belt The little ridge on the end caught the light and appeared like a rib. Also the tensioner is the updated version as well along with the matching AC pulley. This motor is thus, an updated m54b30 so should be parity to what was in the car.



Also inspected all the pulleys (particularly the harmonic dampener) and everything looks surprisingly new.

Of note, the current drive belt is a 1460 (for a Z4M) but spec for 3.0 is a 1453. Go figure. This could be the cause of the random cold start squeels.

I'm not sure what lesson can be learned here but I'll be on my way now

 

[Hairyarse]

Sounds like you got it all covered now

The belt difference could be making the squeal. Seems only a few mm could make all the difference