A few more problems with the E38 740I

Hi Guys

Moved on to a few more problems that I am having with my new purchase...

1. There is a worrying sound that comes from underneath the car. I can only describe it as a VERY LOUD mosquito...but loud enough to be heard in the car while driving...and very pronounced when you have the windows open. It seems to be directly related to the engine revs and gets louder the higher the engine revs. It seems to be coming from underneath the car around the area of the autobox. It also seems to make this noise just as the car changes gear aswell...acompanied by a loud "Wheeeeeesh" sound. The noise is a lot less pronounced when the car is up to normal temp, but it is still there!

2. The car always seems to think that I want the heater on in the cabin! I can tell it that I want the temp to be 16C, and it will blow red hot hair out of the floor and window vents...but blows cool air out of the face vents??? The only way that I can avoid being cooked it to manually turn off the window and floor vents on the control panel!

3. The car seems to run VERY roughly when cold. After I start her, she barely idles at 300RPM and will splutter and buck and shudder until the computer kicks in and revs it to 1100RPM. Even then, I get the "Battery Charge" light coming on and the car makes loud booming noises from the rear silencers... After she gets off the blue zone though, all is well!!!

Any ideas very welcome ...

Thanks

BB

Hey Sporty1

The sound is definately rev related...cos if you shift into neutral while coasting, you cannot hear it anymore...

I was also thinking the cabin air sensor as I can hear the fan is battling to turn when I get into the car. Almost sounds like it is binding on something or is covered in dust.

I checked on Realoem, but that switch is listed as a Double Temperature Switch. Is this not the switch that engages the low and high speed on the aux cooling fan?

Thanks

BB

Hey

Based on what I have managed to find on this website, it sounds like the ATF pump is gone and needs to be replaced. From what they say, it should not be the torque converter becuase it makes the noise irrespective of the gear it is in and revving in park will produce the noise...it would also tie in with my statment that it suddenly makes a much louder wooooooosh noise as it changes gear...as the demand on the pump increases due to a need for more pressure...

http://transmissioncenter.net/Transmission_Noise_Help.htm

I have had a look at nearly all of realoem and have found nothing! That sensor that you pointed out must be the Coolant Temp Sensor and Coolant Guage Sender in one, unless it is integrated into the thermostat...cos when I replaced the gasket, there is a plug connector to the thermostat, which I assume controls the thermostat electronically...

The M60 has its coolant temp sensor mounted on the back of the engine in the coolant manifold. The M62 mentions nothing about this, but does have the sensor that you mention above, plugged into the waterpump...whereas the M60 does not have this sensor...

BB

...will try unplugging it tonight and see what happens...

You make a good point ...

The noise does not totally dissapear when warm, just a lot quieter. I wonder if this could be because the oil is hotter and therefore thinner and therefore not putting as much strain on the pump...as when it is cold and thick...

I actually got out of my 525I while it was idling this morning. I heard a very similar noise and that was what prompted me to think it may be the pump. The noise I am hearing from the 7 sounds exactly like a loud fuel pump...that high pitched hissing noise...except it is like 3 times louder and coming from the front of the car...

BB

BB