Finally getting to drive the Z4 Coupe (long)

[cahme]

I reported here over a month ago my 2007 Z4 Coupe purchase, but what I failed to state then was that I bought it with a misfire in cyl #5. In fear of someone else coming behind me to grab it at such a steal, I bought it on the spot for $6k. The misfire would happen only at moderate pedal around 1800 - 2500 RPM and was non-existent under real light or full throttle and would trigger the SES light if the moderate pedal was maintained.

When buying it, I made a comment (to my family) that even if I needed to put in a new engine, it was still worth it at this price, but I was pretty sure it was coil/injector/plug related, but didn't even have time to swap coils and see at the time due to other commitments.

The next day, I drove it home 90 miles and was able to keep the misfire away and parked it around lunchtime. That evening, my son and I swapped out all 6 coils with the old ones from my 335 I had laying around and took it for a short spin. It was only 3 miles total and I was unable to reproduce the misfire at all and codes were clear. Feeling good, we put the engine cover back on and went to start it up again 15 minutes later to the sound of a clacking rocker arm and rough idle. Pull the codes and low and behold have a misfire on #5 again; the car doesn't leave it's spot.

After quite a bit of research, I'm betting on the issue being with a collapsed lifter on the exhaust side, so I order a new set, the timing tool, and VC gasket and pull the VC. The issue does indeed seem like a collapsed lifter on cyl #5, but it's the intake side (oh, crap! I don't have *that* tool). I spin the engine by hand and the rocker goes sideways and the Valvetronic lever falls out. Before I go and buy the $300 tool, I start thinking about if I should try to find a used '09+ assembled head with the updated casting and teflon rectangrings, but wanted to check mine first. I pull the front caps off of both cams and take a peek .. both look really good. I then pull the exhaust cam and this is what I have. Oh, also, sometime during all of this, I realize it's not a collapsed lifter but a valve stuck slightly open. I put air in the cylinder and verified it was indeed open, but a few taps with a rubber mallet and extension to the top of the valve did indeed bring it closed, so I don't believe it was bent; just stuck. At a minimum, I'm going to need new valve guides.

I'm now full force looking for a used head, but can only find ones that are pre '09, completely refurbished ($1200+), or looks in worse shape than mine. I called a few places on rebuilding my head & having the cam bearings re-worked, but never got the confidence from the shops I was expecting, so I ended up buying an '11 N52 complete engine from a totaled 328xi with 80k mi for $1100. Still a bit of unknown, but I didn't truly know my engine either (with 124k mi). I'm now committed to full gaskets (oil pan - kept mine, OFHG, intake, exhaust) as well as a new clutch (no big deal, it does have 124k on it anyway), but now it will be newer & much cleaner.

Two weekends with myself and son, it's all back together and started up for a few short trips around town, about 20 mi total and this car is freakin awesome! My first 5 cars I owned were all 2-seaters from MGB to Corvette and I just love how this thing drives; it really makes my 335 feel big.

I do have a couple of concerns with a bit of coolant loss on the first drive (after it was bleed & filled) and some chirping & surging at cold startup (< 10 seconds) so I'm not completely out of the woods yet, but it did start right up and I didn't miss any connectors or hoses .

[3798j]

Wow! Good story. My fingers are crossed that your concerns don't materialize into anything. Have fun with it.

[boca1]

fantastic job, I need you as my neighbor so learn how to do all that

[cahme]

Well, upon startup this evening, it really didn't chirp/squeak which leads me to believe it's harmonic balancer/belt related. I'll keep an eye on that. Also, I drained a few drops of oil and there was no water, so at least if I'm losing coolant, it's not going into the crankcase!

Thanks, I've been working on family cars since a kid. For the summer when I was 13, my dad bought a Fiat with a spun bearing and we rebuilt the engine. He did alot of work and showed me, but he'd also leave me the Chilton's manual with a page folded while he went to work and I'd tool around on it. He'd also let me drive around in the country on weekends (still 13) and I've loved cars my whole life. My son is 18 now and hadn't shown much interest in cars until he got his license, but he was thrown into it whole hog with this project.

I took a surprisingly few pictures, mostly because my hands were very grungy and the ones I did take were more to be sure I could put it all back together . The more I tore into it the more depressed I got swapping the entire engine. The old one was in really great shape, well except for the cam and stuck lifter. I didn't have much service history and the previous owners, since 2010, had it serviced at an indy without any documentation to give me. I could've drank the coolant mistaking it for kool-aid, the top of the head was very clean with no sludge whatsoever, and the backs of the valves looking through the intake runners were shiny & super clean.

I had contemplated just changing the heads from the newer engine to mine. I ended up going for the full swap due to
- the engine came with a 6 mo warranty and I figured it'd be much better if I had issues if I kept the engine complete
- the oil pan and all around it was grungy; I inspected the previous owners garage spot and there were not signs of leaks, but there was seepage and lots of grunge on the under-belly panels
- a head gasket + new bolts is > $150; I figured I'd rather spend that on light-weight, high tech Aluminum engine bolts instead (actually came out ahead here)
- pulling the engine forces the clutch change and makes the exhaust manifolds so much easier

The biggest surprise to me, though, was the clutch. It looked less than half used @ 124k miles and the PO mentioned they were a bit worried about that coming up and were a bit worried/scared of what that bill might be, so I know they didn't have it changed. I bought my 335 with 113k miles on it and the clutch was toast at 118k miles.

We're in flood warning rain today and the next, but I should be taking it to work on Thur!

[Huz-Z]

Awesome - I wish I could do work like this on my own. Let me get this straight - so far, you are in about $7500 for a Z4 coupe that is now running nicely and other than those now fixed engine issues, is in darn good shape? Wow!

RESPECT!!

[wdb]

I could be wrong but I believe all Z4 coupes in the US were 3.0si. If so you are losing some hp with your replacement engine. I beleive you should be able to recover them by swapping intakes, but I am not 100% certain.

[Huz-Z]

Originally Posted by wdb

I could be wrong but I believe all Z4 coupes in the US were 3.0si. If so you are losing some hp with your replacement engine. I beleive you should be able to recover them by swapping intakes, but I am not 100% certain.

Yes. If the N 52 that the OP bought was tuned for 215 hp then it should be possible to use the original intake that was fitted to the coupe.

[cahme]

Yes, I kept the original intake manifold. Also, the oil pan and oil pump pickup tube was used from the original Z4 engine as the donor vehicle was a 328xi so it had a completely different oil pan.

That is a good catch, though!

[Huz-Z]

If you have the VIN of the donor car, you can likely use an online BMW VIN decoder to find out if the donor engine was tuned for 215 hp or 255 hp.

[cahme]

The donor car was definitely not a 255hp car, but since I kept the Z4 SI 3 stage intake and tune, I'm sure I've still got the 255hp setup.