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Thanks guys!

Im gonna disconnect the battery every night till the weather is nice enough to work on it.
not that its doing anything over night but it will calm my nerves after the last electrical fire debacle.

The easiest thing 2 do would be to unplug 2 pump (

or the relay in the DME box. As I wrote above the relay switches power to the air pump and the DME controls the relay.

Im 100% sure its the air pump

first months of ownership i thought it was the pusher fan turning on but one day i was standing in front of the car with the hood open and engine running and it turned on. Was NOT the fan was the air pump behind the bumper.

This is scaring me cause last time electrical things were bugging out the car went on fire after sitting for 9 hours.

the air pump will not turn on it traffic >>

you can confirm its the air pump by unplugging it before a cold start. If you still hear the noise look at idler pulleys and belt driven accessories.

It IS the air pumps guys

I got that video from an m5 forum, watch the whole thing it stops after the 120-130 seconds.
But his only turns on for the cold starts.

Very weird. Why does mine turn on randomly? I noticed it happens in stop and go when im being lazy with the gas pedal and the car almost stalls out on take off. Does it think it just restarted maybe? but if its only cold starts that wouldn't make sense since the car was at operating temp.

BTW my noise stopped for now but i know for sure that pump turns on in traffic.

AND I'm 100% sure it was the same exact noise as the video.

Andreas
Queens NY
BMWCCA# 186796
86 325es (wrecked by careless driver)
87 325 300k (project for life)
00 540is 6spd 180k (daily driver)

+1, that's definitely not air pump, as JimLev said

it's probably bearing. If you have stethoscope, you could find the exact source, just be very carefull with engine running.



1998 BMW 540i 6 speed
Arctic silver, M sport suspension (euro delivery), prod. date 05/98, non VANOS
Staggered 18" style 32 OEM wheels
3.15 open differential
Remus exhaust
AFE CAI with improved heat shield
Z3 shifter
VDO oil pressure and temperature gauges in place of headlight/fog switches
Powder coated valve covers-satin black
CDV delete
Debadged
AEA DRL module (aftermarket daytime running lights)

1997 BMW 528iA
Alpine white, premium package, prod. date 04/97, single VANOS
Staggered 17" style 32 OEM wheels
Debadged
AEA DRL module
Custom made sun blinds for rear seating area

2000 Nissan Frontier Desert Runner, AKA "The Work Horse"

Garage aids:
Direct Lift Pro Park 8
Campbell Hausfeld 28 gallon oil lubricated air compressor
Newair ACP-1400H portable air conditioner and heater
Auto Enginuity scan tool with BMW enhanced option
Actron 9135 scan tool-for quick readouts

Sounds like a bearing, check the idlers, etc (m)

The secondary air pump runs at a much faster speed than the sound in your video.
If you speed up your engine does the pitch of your squeal change? If so, this would indicate something that one of the belts is turning.

This is exactly what i heard

What controls it? what can be triggering mine? my coolant temp sensor works fine.






Click if embeded video does not work

Andreas
Queens NY
BMWCCA# 186796
86 325es (wrecked by careless driver)
87 325 300k (project for life)
00 540is 6spd 180k (daily driver)

Yes, we're sure

"Drive It Like You Stole It, A Sickness for Quickness"
The Bottle Rocket "King of Spray" 2 Stage Nitrous Oxide
Dare to be different and stand out among the crowd of me-to-cars!
No guts, no glory! Tire smoke, not traction control!
Zionsville all aluminum radiator to replace the 3 leak prone Nissens Radiators!

NOS Progressive 2 Stage Controller with port injection
Snow's Performance Methanol/Water Injection
Dinan downloads, VAC Under Drive Pulleys
Dinan Carbon Fiber CAI
Dinan Front Strut Bar
Electric Cooling Fan w/PWM controller
NGK Iridium Plugs
DDE Enhanced Angel Eyes, Smoked Lenses
Koni FSD's/H&R Springs, BAV Brass Caliper Bushings
Eisenmann Race Exhaust (from H8-Rain's car)
///M5 3.15 LSD
///M5 Sway Bars, Front & Rear
Energy Suspension Polyurethane Sway Bar Bushings
///M5 Gauge Cluster Rings ///M5 Lip Spoiler
///M5 Mirrors and Switches
Leather Z weighted shift knob (thanks H8-Rain)
Rogue “Octane” Short Shift kit w/WSR
Rogue Tranny Mounts
StopTech Brake Lines Front & Rear
Axxis Deluxe Plus pads Front & Rear
Staggered M Parallel 66, Xenons
Modified CDV, UGDO
Euro Storage Tray (thanks Zombywolf)
Redline in Diff and Tranny
Passport 8500 X50, Escort ZR3 Laser Jammer
G-Tech/Competition Pro Data Logger
Auto Enginuity OBD-II Scan Tool
25% Tint, X-Pel, LoJack
PIAA Driving Lights
BMW CCA Member Boston Chapter

I wonder if you have short somewhere causing

pump to come on and off randomly.



1998 BMW 540i 6 speed
Arctic silver, M sport suspension (euro delivery), prod. date 05/98, non VANOS
Staggered 18" style 32 OEM wheels
3.15 open differential
Remus exhaust
AFE CAI with improved heat shield
Z3 shifter
VDO oil pressure and temperature gauges in place of headlight/fog switches
Powder coated valve covers-satin black
CDV delete
Debadged
AEA DRL module (aftermarket daytime running lights)

1997 BMW 528iA
Alpine white, premium package, prod. date 04/97, single VANOS
Staggered 17" style 32 OEM wheels
Debadged
AEA DRL module
Custom made sun blinds for rear seating area

2000 Nissan Frontier Desert Runner, AKA "The Work Horse"

Garage aids:
Direct Lift Pro Park 8
Campbell Hausfeld 28 gallon oil lubricated air compressor
Newair ACP-1400H portable air conditioner and heater
Auto Enginuity scan tool with BMW enhanced option
Actron 9135 scan tool-for quick readouts

Re: Air pump screeching

Is it only cold starts or all kinds of starting? Maybe my dme thinks its stalling out and restarting?

Andreas
Queens NY
BMWCCA# 186796
86 325es (wrecked by careless driver)
87 325 300k (project for life)
00 540is 6spd 180k (daily driver)

You guys sure??

In the summer it would come alot on in traffic for about 30 seconds at a time. When it came on last night was after i got stuck in a little snow and had to spin the tires a few times. I thought this pump comes on to cool off the cats when they are to hot. And yes I'm sure I'm not hearing the electric fan on the front of the condenser.

Andreas
Queens NY
BMWCCA# 186796
86 325es (wrecked by careless driver)
87 325 300k (project for life)
00 540is 6spd 180k (daily driver)

Right, pump should only come on when the car is (m

first started and the engine is cold. The secondary air pump is powered from relay K6304 (in DME box), which is controlled by the DME.
If it is the air pump that is making the noise (and not an idler pulleys, AC, alt, or waterpump) hope for the relay to be bad, otherwise it's going to be a pricy fix.
The fuse for the pump is under the pass side carpet.

Re: Air pump screeching

The pump will not come on in stop and go traffic. It runs for 10-120 seconds (or something like that) at startup ONLY. Unless you were shutting the engine off in this stop and go traffic or I misread your post you heard something else.

Air pump screeching

Car sat all day in the snow and it was really icy today. I went for a 40 mile drive, when i got off the highway and was in stop and go traffic I heard the air pump turn on as normal but it was screeching like a loose alt. belt. I remember a few threads on a problem with the egr system and water building up in the pump. I'm assuming the water in the pump froze and is causing this noise.
Can anybody point me in the right direction? I always thought this was a M50 problem.

Andreas
Queens NY
BMWCCA# 186796
86 325es (wrecked by careless driver)
87 325 300k (project for life)
00 540is 6spd 180k (daily driver)