BMW Z3 VANOS Issues, Help with Repair Experience Needed

Hey there! I had a similar issue with my 1998 BMW M3 last year, and I have some experience working on cars (though I'd say low to moderate experience level). Like you, I had rough idling, check engine light, and significant power loss. I initially thought it might be something simpler, but after taking it to my trusted workshop, they diagnosed a faulty camshaft solenoid valve. Cost me about 250 Euro for the fix, including parts and labor. They had to replace one of the VANOS solenoids and check the electrical connections. The whole repair took about 3-4 hours, and the difference was night and day. Engine ran smooth again, and fuel economy went back to normal. Before I can share more specific advice, could you share: Have you scanned for error codes? When did these symptoms first appear? Does the problem get worse when the engine is warm? What kind of maintenance history does your Z3 have?

Thanks for sharing your experience! My Z3 is currently at 197417 KM, and I just had it serviced last month. I did scan for codes and got P1520 and P1523, which points to VANOS issues from what I've read online. The symptoms started gradually about three weeks ago, but definitely got worse in the past week. The problem is actually more noticeable when the engine is cold and seems to improve slightly when warm, though the power loss is still there. Good to hear your repair cost was reasonable, I was worried it might be a much bigger expense. I've been pretty diligent with maintenance, but haven't had any VANOS-related work done before. Did your repair involve just the solenoids, or did they have to get into the VANOS unit itself? I'm trying to get an idea of what I might be looking at cost-wise.

Hey again! Thanks for those details. After fixing my M3 last year, I actually discovered that the initial solenoid replacement was only part of the solution. A few months later, the same symptoms started creeping back, and it turned out the VANOS unit itself needed attention. The cold-start issues you're describing sound really familiar, that's exactly how mine behaved. With those codes and symptoms, especially at your mileage, I'd bet you're looking at more than just solenoids. My complete VANOS rebuild ended up costing around 800-900 Euro, but it was totally worth it. The shop had to replace the seals, springs, and do some machining work on the unit. When they opened up my VANOS unit, they found worn seals and a bit of scoring on the piston, pretty common issue at higher mileages. The rebuild took about a day and a half, but the car came back running like new. Power delivery was smooth again, especially in the lower rev range where these cars really shine. Quick tip though, make sure whoever works on it really knows BMWs. My first mechanic missed some of the wear indicators, which is why I ended up needing more work later. Have you noticed any rattling noise from the engine bay? That's usually another good indicator of VANOS wear.

Thanks for the detailed response! Yeah, now that you mention it, there is a slight rattling noise, especially during cold starts. Your experience is really helpful, sounds like I should prepare for a full VANOS rebuild rather than just hoping it's the solenoids. At least I know what I'm potentially dealing with now. I'll make sure to find a BMW specialist for this job. Last thing I want is to pay for a partial fix and end up doing it all over again in a few months like what happened with your M3. The car's been great otherwise, so investing in a proper repair seems worth it to get it running right again. I've got an appointment scheduled with a specialist shop next week. Going to bring up everything we've discussed here, the cold start issues, the codes, and the possibility of a complete rebuild. Really appreciate you sharing your experience, helps a lot with knowing what to expect! Would you mind if I messaged you after the repair to let you know how it went? Might be helpful for others with similar issues too.