New 740 owner with questions???

[ABQbimmer]

I purchased a 2000 740iL over 2 years ago and it is the best highway car I have ever driven. It did come with some problems so I hope somebody can help. I live in the Southwest so when it gets over 100 degrees the radio goes out and the on-board computer stops work but the car does drive normally. I start receiving error messages, is this normal? Any solutions? I also have a water leak coming from the lower hose on the radiator but I know it isn't the hose, does the radiator need to be replaced. Looking into different wheels, any suggestions I'm trying to decide if I should invest more money into car, 93K miles, but addicted to the highway comfort of the car.

[IcemanBHE]

Sounds like the MID/RAdio has a crack someplace in the Motherboard that expands and disrupts the circuit. As for messages? Please tell us what they are. I know they have nothing to do with the MID/Radio problem because I have driven mine without this being plugged in.

As for the leak. These are known for leaking expansion tank. Also check vent screw on top of radiator and the cap itself.

Nothing wrong with fixing these problems. They all do it at some point.

As for wheels...you cam to the right place.

Everyone here has an opinion. :)

[ABQbimmer]

I get various messages and dashlights coming on. I will get the traction control light, brake light, air bag light on at the same time. I can't operate the on-board computer to do things such as comsumption, distance, etc. When it got to 110 degrees I received the trans safe fail mode message. Is there a thermal switch somewhere that needs to be replaced? While all these lights are coming on the car operates normally.

[IcemanBHE]

Wow. So ASC, ABS, and SRS come on simultaneously? OBC is directly related to the MID, so Im not surprised you have that issue. Trans fail safe is a generic problem that appears usually having nothing to do with transmission. lol In the E38 its usually low battery.

SO..... My best guess for everything but the MID/OBC is failing battery. How old?

These cars are super funky when getting LOW voltage supplied from battery. You should have ~14v DC at the battery or the jump posts in the engine bay.

Please check and report back. If battery is fine then I have another test for you.
B

[ABQbimmer]

I finally got time to check the battery voltages:12.3V sitting, 12.14V with key on ACC, 13.3V when car is on. This was done when things were operating normally. The battere is a 85 month and it is about 2 years old. Another thing I notice is that the outside temp is reading about 8-10 degrees higher than the real temp. I still think it is an heat issue because as soon as the radio comes back on all the other lights start going off. Is there a cooling vent for the electronics that may not be working? Send me your other test and I will check that.

[IcemanBHE]

OK. Remove the battery cables from the battery. Connect the two cables together, wire whatever, but so they touch and make an electrical connection. Leave like this overnight. Reconnect battery.

Any difference? This resets all the electrical goodies, as all the modules are drained of power. Some modules can retain power for HOURS due to capacitors.

[Derekj]

Check ignition switch.

[imola740i]

wow:eek: that iceman is knows his bmws

[IcemanBHE]

Aww thks lol But some would argue :)

Ive owned lot sof BMWs and do most of the work myself. So Ive learned. Still am. We all have knowledge that others can learn from.

And...my indy is a good pal and a BMW Master Mech. So when I get stumped, we solve it together.

My next thing...Im going to build me a GT1 like Edwin has. I get tired of borrowing my pals.

[ABQbimmer]

Finally getting back to the problem. I disconnected the battery cables and shorted them for 3 days. The problem came back. The radio doesn't come on and this time the fasten seatbelt indicator stayed on. The onboard computer stuff was accessible but the BC lever didn't affect anything. When I started to drive at night the interior lights would come on randomly. None of the steering wheel controls worked. I also think is is harder to steer, especially notice this on corners. The temperature here has cooled to the 60's. It seems like the system is hanging up, does it need to be reflashed or something along these lines? The car drives normally except for the extra effort in steering.

[bstar]

Voltage

[IcemanBHE]

OK. Start the car. Flip down the passenger visor and open the mirror.

If it does anything unusual (new errors, lights, radio off, tilt wheel moves, etc), you need a new ignition switch.

Seeing this more and more now on these older cars. Ive personally not seen this, but others here have. Do a search on faulty ignition switch.

[ABQbimmer]

Tried the passenger mirror thing and no problems. If it is a voltage thing any ideas where to start checking? Is the alternator ready to die? I don't notice any flickering in the lights when the car is sitting at idle. Stumped!!!