Noise after turning car off

[Dave1027]

This is probably normal but I thought I should check it with the experts. My ZHP, after driving home and turning it off in the garage, something continues to run. It sounds like an electric motor and I think it may be the SAP. It runs for a while, maybe a few mintues and eventually shuts off. Also, there is a slight knocking sound coming from the rear area, maybe fuel pump? I have a feeling it's all emissions related.

[danewilson77]

Dunno about the rear sound. The other sound is normally reported.

[bmwcats]

I have the same electric motor sound too, I have no idea.

[Avetiso]

+1. I have it too.

[nike001]

Same here.

I get a couple clunks when it turns off sometimes too.. also reported normal

[danewilson77]

It sounds to me, like the electrical circuits are discharging after shutdown, but I'm probably hearing my AE's.

[LivesNearCostco]

I sometimes get the same type of electric motor sound. Don't know if it's heater pump, DISA de-energizing, VANOS solenoids, ventilation blower fan, electric cooling fan, etc. Shouldn't be the SAP which should only run on cold startup.

[Dave1027]

I'll try to localize the sounds. I got a feeling they have something to do with fuel vapors/evap system. My Toyota truck does something similar. Not near as loud though. On the Toyota, you have to be outside the truck with absolute silence or you can't hear it. With the ZHP, I can hear it sitting in the driver's seat.

[Johnmadd]

The front could just be the fan and the rear may be just the crackling of the catalytic converter. You have an automatic transmission correct?

[Stewbie]

I get this too. I was guessing fuel pump but haven't spent any time trying to localize it.

[BavarianZHP]

Is the sound normal for a few minutes as the OP stated? I've never had anything run that long after shutting it down. This may be related to the rear noise (not sure) but whenever I open the trunk, a hissing/buzzing noise can be heard for a while near the taillights - I assume this is normal...

[Dave1027]

The front could just be the fan and the rear may be just the crackling of the catalytic converter. You have an automatic transmission correct?

Yes, AT. So the electric pusher fan runs when I don't have the AC on and even after shutting the car off?

I agree it is possible the knocking is coming from the exhaust going by the sound of it.

[Johnmadd]

Yes, AT. So the electric pusher fan runs when I don't have the AC on and even after shutting the car off?

I agree it is possible the knocking is coming from the exhaust going by the sound of it.

It shouldn't... does it though? If so final stage resistor would likey be the culprit.

[shanneba]

The SAP would normally only run on a cold start.

The sound is probably the tank leakage test for the EVAP system.
It will run a longer time when the gas tank is closer to empty.
It runs every other time when you turn the car off, when a set of conditions are met:

See pages 18-20 of this document- http://www.bmwmotorsports.org/BMW_docs/m54x5.pdf

LEAK DIAGNOSIS TEST PRECONDITIONS
The ECM only initiates a leak diagnosis test every second time the criteria are met. The criteria
is as follows:
• Engine OFF with ignition switched OFF.
• Engine Control Module still in active state or what is known as “follow up mode” (Main
Relay energized, control module and DME components online for extended period after
key off).
• Prior to Engine/Ignition switch OFF condition, vehicle must have been driven for a minimum
of 20 minutes.
• Prior to minimum 20 minute drive, the vehicle must have been OFF for a minimum of 5
hours.
• Fuel Tank Capacity must be between 15 and 85% (safe approximation between 1/4 -
3/4 of a tank).
• Ambient Air Temperature between -7C & 35C (20F & 95F )
• Altitude < 2500m (8,202 feet).
• Battery Voltage between 11.5 and 14.5 Volts
When these criteria are satisfied every second time, the ECM will start the Fuel System Leak
Diagnosis Test. The test will typically be carried out once a day i.e. once after driving to work in the morning, when driving home in the evening, the criteria are once again met but the test is not initiated. The following morning, the test will run again.

[Dave1027]

It shouldn't... does it though? If so final stage resistor would likey be the culprit.

Just so I'm understanding correctly, the FSR controls the heater/ac blower fan. If I feel it still blowing air after I shut off the car then the FSR is bad?

[danewilson77]

Just so I'm understanding correctly, the FSR controls the heater/ac blower fan. If I feel it still blowing air after I shut off the car then the FSR is bad?

You'll know for sure if the FSR is bad...imo.

[Dave1027]

The sound is probably the tank leakage test for the EVAP system.
It will run a longer time when the gas tank is closer to empty.
It runs every other time when you turn the car off, when a set of conditions are met:

See pages 18-20 of this document- http://www.bmwmotorsports.org/BMW_docs/m54x5.pdf

LEAK DIAGNOSIS TEST PRECONDITIONS
The ECM only initiates a leak diagnosis test every second time the criteria are met.... When these criteria are satisfied every second time, the ECM will start the Fuel System Leak
Diagnosis Test. The test will typically be carried out once a day i.e. once after driving to work in the morning, when driving home in the evening, the criteria are once again met but the test is not initiated. The following morning, the test will run again.

Excellent information. Seems my car is on the opposite schedule then. It runs after coming home from work. :)

Thanks for your very informative post. That's sounds like exactly what is happening. Question: So the DM-TL pump can run for up to 4.5 minutes depending on how much leakage there is? Maybe the knocking I heard is the pressure change of the fuel tank?

[shanneba]

Maybe the knocking I heard is the pressure change of the fuel tank?

It may be the purge valve or change over valve being activated/deactivated.

[Dave1027]

The knocking sound I reported did turn out to be exhaust cooling off.

[M3TA5IN]

The e90 does weird electrical stuff when I shut it off too. It will cycle for quit awhile actually. I've stayed in the car with everything off for 10 mins and every little bit it sounds like an electric motor cycles.

I've been outside after the car has been off for hours and heard the car making the same noise.


Sent from my fancy city machine.