deep loud humming noise in cabin before startup
 

Hi to all, well I have noticed recently that just before starting up I hear a loud deep humming noise (and am sure it isn't the console fan) I say whilst starting up as I have a diesel engine and turn the key one notch and wait 15-20 seconds before firing x5 up.

Only thing that has changed is that on the 2nd dec I swapped out dying OEM battery for a bosch silver plus rated at 100ah/ 830cca as opposed to the oems 90ah/720cca...not an issue just curious

I can't help you with the humming noise. I haven't noticed any humming, except for the fan starting and all the vents opening up.
Cyprus isn't very cold, is it? In temperatures under approximately 5c the webasto fires up (if your car has webasto). That might make a humming noise.

But I'm very curious about why you would turn the key and wait for 15-20 seconds before starting up? Pre-heat/glowing? If that's the reason, you can just quit doing it.
The preheating is done before you start up, even if you put the key in and turn it to pos 3 (start) right away. I've had the "PRE HEATING" message come up twice, it was on for less than a second before it disappeared. The outside temperature was around -10c.
As long as you don't see the Pre-Heating message in your instrument cluster, you can just start it right away. If it doesn't fire, your glow plugs and/or glow-relay is faulty.

The X5 isn't a 35 year old diesel Benz :)

Sounds like the air pump waking up for the suspension to be topped off. Mine has a leak and does this sometimes. The cold weather is making it worse too.

thanks fella, I am sure I read in the glove box manual a while back for the diesel version that you should turn key wait a little while then fire up....didn't specify whether to do this in cold conditions or average temps, either way do you fellas know what fuse will 'disable' the webasto? or should i just disconnect the two connectors on it? or will this cause issues?....I am still trying to figure out if this webasto thermotopz, is to help the engine warm up? or to provide hear for the cabin in very cold temps whilst the engine heats up in the meantime......

The Webasto is meant to help the engine warm up. If you have the remote control, or the "Aux vent/heating" menu on your navi screen, it can warm up the engine, as well as warm up the cabin when the engine is switched off.
It burn diesel to heat up the coolant, thus making the engine and cabin warm up faster. The owners manual states that even in the summer time, the Webasto should be manually switched on for 5 minutes now and then, just to run it. If you don't have the "Aux vent/heating" option, it will only say "Auxilary vent" or something like that.

I'm not near my car right now, but I can check if the Webasto has it own fuse later.

If you disconnect the cables or remove the fuse, I'm pretty sure it will throw fault codes. Every single E53 diesel I have seen, has the Webasto. So I guess it's there for a reason. I wouldn't disconnect it permanently, if I were you.

rolfi thanks, I have found out it is fuse 59 to disable the heater....and am in two minds about removing fuse if it throws a fault code....however as you said looking at the guide i dug up it seems to do 3 things


http://www.elektromobily.org/w/images/1/13/Webasto.pdf


thermo Top Z/C2 General Description
201
2. General Description
The water heater Thermo Top Z supplementary heater is
intended to compensate for the shortage in heat
generated by engines optimised for low fuel consumption.
The water heater Thermo Top C auxiliary heater is used
to:
• heat the vehicle cabin,
• defrost the vehicle windscreens,
• preheat water-cooled vehicle engines.
The supplementary heater Thermo Top Z may be
converted into an auxiliary heater using a retrofit kit


and Rolfi digging around in some old emails I found below answer to question i raised with webasto

Q.I have a webasto thermotop z in my bmw x5, should this function automatically if the temperature falls below 5C?

Answer.
Dear Sir,
The Webasto Thermo Top Z is used as an auxilary heater. This means it will provide heat when needed and the vehicle heating system is not able to provide it. The switching on and off of the TT-Z is controlled by the vehicle system, but +5 degrees Celcius is a commonly used temperature to switch on an auxilary heater.
Apart from the temperature, also another condition is needed, e.g. engine running (otherwise the heater will also run when the car is parked).
For some vehicles it is also possible to upgrade the auxilary heater to a parking heater. This means the Webasto heater can be started stand alone and will be able to pre-heat the vehicle. Please contact your BMW workshop for the possibilities for your car.
Hopefully this answers your question.

Kind regards,

Jan Dekens
Technical Support Engineer

Webasto Product International (NL)
Global Comfort Solutions
P.O. Box 41, NL-8260 AA Kampen
Constructieweg 47, NL-8263 BC Kampen
The Netherlands
Phone: +31 (0) 38 3371160

Good thing you found it. I forgot about it :p

But I did look in the manual under starting, and it said that the engine can be started as soon as the "Pre-heating" message disappears. If it doesn't show up, it's not cold enough or the pre-heating is already done :)

And yeah, it can be converted into a auxiliary heater. If you have the electronic water pump, it's just a matter of coding. I enabled it with BMW Scanner 1.4.0. It's one of the best things I've ever done :) Cold mornings are no longer unbearable! I consider the BMW Scanner 1.4.0 cable the best spent $18 in my whole life :D