Reliability Z4M vs M3 e46

[rif75]

Dear all,

I have seen a lot of threads about the M3 e46 reliability but not much for the Z4M.

I have been lucky enough to own all M3s since the e46. Lately, I have been driving F80 et even G80 but I have been missing so much the old natural aspirated 6L that I bought a E36 3.2 321cv cabriolet and was also looking for a E46 manual transmission but almost impossible with less than 200000km or it would be very expensive...

I have a good opportunity on a coupe Z4M with 115000km from 2007 and I love the test drive so I will probably go for it but I was wondering before signing if even the 2007 M cars have the same issues as M3 e46 such as :

- Head gasket failure
- Rear axle tear
- rod bearing recall (guess not for a 2007 s54)

If I have missed anything or something only related to E86, thanks for sharing

Regards,

[maupineda]

They are mechanically the same, so engine wise are the same, VANOS and Rod bearings are the biggest concerns, but I feel VANOS concern is way out of proportion. Rod bearings may be an issue depending on how the car was treated by prior owners.

The Z4M does not have the structural issues the e46 has. I would say the Z4M is a more robust vehicle.

[86Zed]

Well stated by maupineda . In todays market you can get a whole lot more Z4M (coupe or roadster) for the same money vs an E46 M3. Doesn’t make sense but that is the way it is

[07ImolaRot]

I own both. All the S54 issues are shared. Z4M has none of the RACP issues or SMG issues obviously. It is also more fun to drive, more unique and overall the ratio of unmolested cars in existence is higher. Nowadays it is the better car to buy. For 40 grand you can get yourself into a clean low mileage Z4M. It is not as popular or as beautiful but you also wouldn't be spending 10 grand swapping in a brand new axle carrier.

[vt100]

Originally Posted by rif75

if even the 2007 M cars have the same issues as M3 e46 such as :

- Head gasket failure
- Rear axle tear

Wait, head gasket failure and rear axle tear (btw, what does the latter mean?) are common on e46 m3?! Never heard of either

[rif75]

Thank you all for your feeback. Helps a lot.

For the head gasket, I tought it was maybe solved since the ref on etk changed 3 time :

Part number Production ended
1 11127835918 production
2 11127833736 11.02.2004
3 11127832022 13.11.2003

I guess I will plan the rod bearings and see also for the vanos.

[rif75]

Originally Posted by vt100

Wait, head gasket failure and rear axle tear (btw, what does the latter mean?) are common on e46 m3?! Never heard of either

Just type that on google and you will see a lot of pictures...

rear axle cracks bmw m3 e46

[GuidoK]

Originally Posted by rif75

rear axle cracks bmw m3 e46

I think you mean rear subframe mounting point issues (cracks in the monocoque at that spot).

The z4m doesn't have those issues. The way the axle subframe is mounted in the monocoque is different: the bottom chassis tension struts (the ones you screw on the monocoque bottom) go on the z4 chassis from the monocoque to a mounting point behind the rear diff/subframe, effectively creating a box section where the axle subframe sits in (so those tension struts encapsule both the fuel tank and the rear subframe), and with the e46, those tension struts mount mount to a mounting point in front of the rear subframe, so they only encapsule the fuel tank and not the axle subframe. So that axle subframe sits in a C section instead of a box section (box section is obviously much stronger).
I think that is the difference why the e46 chassis has all these problems and the z4 chassis hasn't.

Another aspect with the s54 engine is worn camshafts and cam followers. Not as common, but if you get that, it's a lot of money in parts to fix that (and quite a bit of work)

I don't think headgasket failures on the s54 are that common though.

[rif75]

Thank you sir for info. This is what I meant but I am a french speaker so my english is not perfect

I have found this video about the S54 that is quite good

[GuidoK]

Originally Posted by rif75

I have found this video about the S54 that is quite good

One thing that isn't addressed in that video is wear on the oil pump pressure regulating cylinder. This is something not generally found on english forums, but the german forums are well documented on this.
In germany you can also get new DLC coated pressure regulating cylinders (that's a part you can't buy at BMW, only a complete oilpump is sold (€626)).
So if you change the rodbearings (should be done every ~80k km), also check&change that pressure regulating cylinder.

And I think the S54 also has a constant pressure oil valve in the block that can start leaking.

Regarding the vanos, both the tabs on the vanos hub can fail (aftermarket hubs with reinforced tabs are available), but also the little bolts on the camgears can fail (both these problems are well documented though so this shouldn't be a problem to fix/overhaul)

[rif75]

Thanks a lot for those additional info. I take note and try to find a shop in germany to do the bearings with this pressure regulating cylinder.

For the vanos, I am wondering what would be the cost for those reinforced parts and labor...Don't want to spend 5000 in total with the bearings even if I would like to keep that car as long as possible

[Westersund]

Wasn't the VANOS hub bolts a Z4 M S54 only issue? They used different bolts. Or is my mind playing me a trick?

[GuidoK]

Originally Posted by Westersund

Wasn't the VANOS hub bolts a Z4 M S54 only issue? They used different bolts. Or is my mind playing me a trick?

Lots of cases with s54's derived from M3's documented on the www.
Bolts were changed indeed at some point (from m6x14 to m6x16) according to the ETK, but both pre and post 06 engines can develop these issues afaik.

I don't know how those bolts work themselves loose, but if I were to install new ones, I would very meticulously clean the screw holes and the new bolts with acetone and fit the new bolts with red loctite.