2007 Z4 M Coupe Summer Starting Issue

[Z4MC Junkie]

I’ve had this bizarre starting issue for a few years now where I’ll turn the key, the console lights will come on but the starter does nothing. I’ve found that if I then hit the hatch release button, get out the car, open the hatch and get back in the car, the car starts right up. To make this issue even more bizarre, it only happens in warm weather when the car’s been sitting in the sun. Car starts like a champ in the fall, winter and spring. I’ve taken it to my local MB/BMW mechanic multiple times and he’s replaced the battery, alternator and clutch switch but the issue has not gone away. Any thoughts? Thanks!

[bananabun]

Wonder why the mechanic chose to replace the battery and alternator. Were they showing signs of failure?

Mine had a similar intermittent starting issue and it turned out to be the starter motor solenoid going bad. Usually happens before the motor completely fails.

[Z4MC Junkie]

I have this issue for years. I only mentioned the new alternator and battery since they were electrically related repairs/maintenance and this issue is electrical related.

Was your issue weather temperature related like mine?

Thanks!

[bananabun]

Now that you mention it, I think it might have been. It happened a few times last year but wasn't too bad. This year, it got worse during a really hot track weekend recently. Electronics would work but the car wouldn't crank at all. It would start after a dozen or so tries.

Gave the starter motor a good tap with a hammer and socket extender, and it magically started working again.

[Nate4641]

Do you have an aftermarket clutch pedal stop? The switch on the clutch pedal doesn't allow for much play beyond the factory setting. I have a similar issue with my car when it is warm, and my clutch stop is as far back as I can get it. My solution is to turn the key then kick the clutch pedal down hard like I'm starting a dirt bike. There is a way to slightly reposition the switch (if that is your issue), but I haven't done it.

[dfjaws]

Originally Posted by bananabun

Mine had a similar intermittent starting issue and it turned out to be the starter motor solenoid going bad. Usually happens before the motor completely fails.

This may be it. The starter solenoid is a known issue. My starter would work perfectly until every once in awhile it would do absolutely nothing despite the battery having plenty of power. The issue began to creep up more and more and seemed to be exacerbated by heat (trying to restart the car after it was warmed up was a real gamble). Ended up replacing the starter with a new Valeo unit and everything worked perfectly. The DIY is stupid easy as well. I didn't even need to remove the intake or airbox because there's so much room.
This Pelican DIY will give you an idea of what the job entails.

https://www.pelicanparts.com/techart...eplacement.htm

[Daemonblitz]

I replaced my starter for a similar issue. (Car would not crank when hot)
I suggest doing that next.
Not sure why someone would recommend an alternator replacement for a car that doesn't start. Maybe if it died immediately, but an alternator does not cause a no-start situation by itself.

[Z4MC Junkie]

Thanks Bananabun and Daemonblitz. I told my mechanic to check the starter/starter solenoid. Thanks for confirming your issue's relationship to warm temperatures. My issue only happens after my car has sat out in the sun on a warm summer day or when the engine is warm on a warm summer day.

Thanks Nate. My mechanic replaced the clutch switch last week in a failed attempt to fix my issue. I'm, not sure if the new clutch switch included a new clutch stop and/or if the parts he used were after market. I'll ask him.

[couchflyer]

Heat related issue is usually a short some where, solenoid, starter motor are good possibles. Back when cars had coils the coil would start to fail at higher temperatures.

[elerner61]

Originally Posted by Nate4641

Do you have an aftermarket clutch pedal stop? The switch on the clutch pedal doesn't allow for much play beyond the factory setting. I have a similar issue with my car when it is warm, and my clutch stop is as far back as I can get it. My solution is to turn the key then kick the clutch pedal down hard like I'm starting a dirt bike. There is a way to slightly reposition the switch (if that is your issue), but I haven't done it.

I have had this exact heat related starting issue after I installed an aftermarket clutch stop (which I like). I ended up adjusting the clutch stop a little further towards the fire wall and that fixed the problem.

[Z4MC Junkie]

Mechanic told me today that the battery cables and starter checked out and that there was nothing more he could do. I called another BMW shop and they told me the issue was more than likely due to one or more bad contacts (I believe he said there are a total of 8) in the ignition switch and that if that's the problem, I would need a new one switch since you can't clean ignition switch contacts without destroying the switch itself. I guess I'll go down that rabbit hole.

BTW - I have no codes on the code reader.

[XMetal]

A bad starter or bad ignition switch won't throw any codes. It's much cheaper and easier to try out a new ignition switch first.

[Hawkeye]

As an easy check before pulling your hair out... does your car have an aftermarket clutch stop? I see elerner beat me to this one!

My car does this when it is really hot. It is because I installed a clutch stop that is metal that expands just enough to not let me depress the clutch enough to turn the engine. Airing out the car for a few seconds usually does the trick (just opening the window or door). If you have an aftermarket clutch stop might want to check how much travel you have, might just need to screw it in a little more.

[Z4MC Junkie]

Hawkeye - I had this issue with the car's original clutch stop/switch. I had a new clutch switch installed (not sure if clutch stop is part of clutch switch) but that didn't fix the issue.

[Steeler]

Originally Posted by aball65@yahoo.com

Hawkeye - I had this issue with the car's original clutch stop/switch. I had a new clutch switch installed (not sure if clutch stop is part of clutch switch) but that didn't fix the issue.

The clutch stop is attached to the floorboard behind the clutch pedal.
It can be adjusted in or out to suit. In your case it may be adjusted too far out due to the warm weather expanding the materials and not allowing the clutch pedal arm to contact the neutral safety switch.
See if you can wind the clutch stop in a bit.

[Z4MC Junkie]

Thanks. I'll try that and let you know.

[wdb]

Thing with the clutch switch is that you should be able to HEAR it. I can hear mine 'click' when its actuated. If you hear the 'click' (and your switch is new) that is not likely to be your problem.

What mileage is on the car?

[Z4MC Junkie]

The issue was solved by installing a new clutch master cylinder. According to the mechanic, the original one was "wobbly" and therefore would not always make the necessary contact/connection required for starting. I'm now able to start my car after it has been sitting in the sun - what a luxury! This issue was by far the most frustrating issue I've ever had with any car. I appreciate everyone's inputs. Thanks!

[Steeler]

Happy you have it fixed but IMO that does not make any sense.
The clutch MC has no bearing on the electrical system.

Anyhow, happy motoring.

[Sergio19]

The clutch pedal switch is a HAL effect sensor so no, it will not click.

As already mentioned most common starting issue is a bad ignition switch followed by aftermarket clutch stops.